target: add Espressif ESP32-S3 basic support

[openocd.git] / doc / openocd.texi

\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename openocd.info
@settitle OpenOCD User's Guide
@dircategory Development
@direntry
* OpenOCD: (openocd).      OpenOCD User's Guide
@end direntry
@paragraphindent 0
@c %**end of header

@include version.texi

@copying

This User's Guide documents
release @value{VERSION},
dated @value{UPDATED},
of the Open On-Chip Debugger (OpenOCD).

@itemize @bullet
@item Copyright @copyright{} 2008 The OpenOCD Project
@item Copyright @copyright{} 2007-2008 Spencer Oliver @email{spen@@spen-soft.co.uk}
@item Copyright @copyright{} 2008-2010 Oyvind Harboe @email{oyvind.harboe@@zylin.com}
@item Copyright @copyright{} 2008 Duane Ellis @email{openocd@@duaneellis.com}
@item Copyright @copyright{} 2009-2010 David Brownell
@end itemize

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end quotation
@end copying

@titlepage
@titlefont{@emph{Open On-Chip Debugger:}}
@sp 1
@title OpenOCD User's Guide
@subtitle for release @value{VERSION}
@subtitle @value{UPDATED}

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@summarycontents
@contents

@ifnottex
@node Top
@top OpenOCD User's Guide

@insertcopying
@end ifnottex

@menu
* About::                            About OpenOCD
* Developers::                       OpenOCD Developer Resources
* Debug Adapter Hardware::           Debug Adapter Hardware
* About Jim-Tcl::                    About Jim-Tcl
* Running::                          Running OpenOCD
* OpenOCD Project Setup::            OpenOCD Project Setup
* Config File Guidelines::           Config File Guidelines
* Server Configuration::             Server Configuration
* Debug Adapter Configuration::      Debug Adapter Configuration
* Reset Configuration::              Reset Configuration
* TAP Declaration::                  TAP Declaration
* CPU Configuration::                CPU Configuration
* Flash Commands::                   Flash Commands
* Flash Programming::                Flash Programming
* PLD/FPGA Commands::                PLD/FPGA Commands
* General Commands::                 General Commands
* Architecture and Core Commands::   Architecture and Core Commands
* JTAG Commands::                    JTAG Commands
* Boundary Scan Commands::           Boundary Scan Commands
* Utility Commands::                 Utility Commands
* GDB and OpenOCD::                  Using GDB and OpenOCD
* Tcl Scripting API::                Tcl Scripting API
* FAQ::                              Frequently Asked Questions
* Tcl Crash Course::                 Tcl Crash Course
* License::                          GNU Free Documentation License

@comment DO NOT use the plain word ``Index'', reason: CYGWIN filename
@comment case issue with ``Index.html'' and ``index.html''
@comment Occurs when creating ``--html --no-split'' output
@comment This fix is based on: http://sourceware.org/ml/binutils/2006-05/msg00215.html
* OpenOCD Concept Index::            Concept Index
* Command and Driver Index::         Command and Driver Index
@end menu

@node About
@unnumbered About
@cindex about

OpenOCD was created by Dominic Rath as part of a 2005 diploma thesis written
at the University of Applied Sciences Augsburg (@uref{http://www.hs-augsburg.de}).
Since that time, the project has grown into an active open-source project,
supported by a diverse community of software and hardware developers from
around the world.

@section What is OpenOCD?
@cindex TAP
@cindex JTAG

The Open On-Chip Debugger (OpenOCD) aims to provide debugging,
in-system programming and boundary-scan testing for embedded target
devices.

It does so with the assistance of a @dfn{debug adapter}, which is
a small hardware module which helps provide the right kind of
electrical signaling to the target being debugged. These are
required since the debug host (on which OpenOCD runs) won't
usually have native support for such signaling, or the connector
needed to hook up to the target.

Such debug adapters support one or more @dfn{transport} protocols,
each of which involves different electrical signaling (and uses
different messaging protocols on top of that signaling). There
are many types of debug adapter, and little uniformity in what
they are called. (There are also product naming differences.)

These adapters are sometimes packaged as discrete dongles, which
may generically be called @dfn{hardware interface dongles}.
Some development boards also integrate them directly, which may
let the development board connect directly to the debug
host over USB (and sometimes also to power it over USB).

For example, a @dfn{JTAG Adapter} supports JTAG
signaling, and is used to communicate
with JTAG (IEEE 1149.1) compliant TAPs on your target board.
A @dfn{TAP} is a ``Test Access Port'', a module which processes
special instructions and data. TAPs are daisy-chained within and
between chips and boards. JTAG supports debugging and boundary
scan operations.

There are also @dfn{SWD Adapters} that support Serial Wire Debug (SWD)
signaling to communicate with some newer ARM cores, as well as debug
adapters which support both JTAG and SWD transports. SWD supports only
debugging, whereas JTAG also supports boundary scan operations.

For some chips, there are also @dfn{Programming Adapters} supporting
special transports used only to write code to flash memory, without
support for on-chip debugging or boundary scan.
(At this writing, OpenOCD does not support such non-debug adapters.)


@b{Dongles:} OpenOCD currently supports many types of hardware dongles:
USB-based, parallel port-based, and other standalone boxes that run
OpenOCD internally. @xref{Debug Adapter Hardware}.

@b{GDB Debug:} It allows ARM7 (ARM7TDMI and ARM720t), ARM9 (ARM920T,
ARM922T, ARM926EJ--S, ARM966E--S), XScale (PXA25x, IXP42x), Cortex-M3
(Stellaris LM3, STMicroelectronics STM32 and Energy Micro EFM32) and
Intel Quark (x10xx) based cores to be debugged via the GDB protocol.

@b{Flash Programming:} Flash writing is supported for external
CFI-compatible NOR flashes (Intel and AMD/Spansion command set) and several
internal flashes (LPC1700, LPC1800, LPC2000, LPC4300, AT91SAM7, AT91SAM3U,
STR7x, STR9x, LM3, STM32x and EFM32). Preliminary support for various NAND flash
controllers (LPC3180, Orion, S3C24xx, more) is included.

@section OpenOCD Web Site

The OpenOCD web site provides the latest public news from the community:

@uref{http://openocd.org/}

@section Latest User's Guide:

The user's guide you are now reading may not be the latest one
available. A version for more recent code may be available.
Its HTML form is published regularly at:

@uref{http://openocd.org/doc/html/index.html}

PDF form is likewise published at:

@uref{http://openocd.org/doc/pdf/openocd.pdf}

@section OpenOCD User's Forum

There is an OpenOCD forum (phpBB) hosted by SparkFun,
which might be helpful to you. Note that if you want
anything to come to the attention of developers, you
should post it to the OpenOCD Developer Mailing List
instead of this forum.

@uref{http://forum.sparkfun.com/viewforum.php?f=18}

@section OpenOCD User's Mailing List

The OpenOCD User Mailing List provides the primary means of
communication between users:

@uref{https://lists.sourceforge.net/mailman/listinfo/openocd-user}

@section OpenOCD IRC

Support can also be found on irc:
@uref{irc://irc.libera.chat/openocd}

@node Developers
@chapter OpenOCD Developer Resources
@cindex developers

If you are interested in improving the state of OpenOCD's debugging and
testing support, new contributions will be welcome. Motivated developers
can produce new target, flash or interface drivers, improve the
documentation, as well as more conventional bug fixes and enhancements.

The resources in this chapter are available for developers wishing to explore
or expand the OpenOCD source code.

@section OpenOCD Git Repository

During the 0.3.x release cycle, OpenOCD switched from Subversion to
a Git repository hosted at SourceForge. The repository URL is:

@uref{git://git.code.sf.net/p/openocd/code}

or via http

@uref{http://git.code.sf.net/p/openocd/code}

You may prefer to use a mirror and the HTTP protocol:

@uref{http://repo.or.cz/r/openocd.git}

With standard Git tools, use @command{git clone} to initialize
a local repository, and @command{git pull} to update it.
There are also gitweb pages letting you browse the repository
with a web browser, or download arbitrary snapshots without
needing a Git client:

@uref{http://repo.or.cz/w/openocd.git}

The @file{README} file contains the instructions for building the project
from the repository or a snapshot.

Developers that want to contribute patches to the OpenOCD system are
@b{strongly} encouraged to work against mainline.
Patches created against older versions may require additional
work from their submitter in order to be updated for newer releases.

@section Doxygen Developer Manual

During the 0.2.x release cycle, the OpenOCD project began
providing a Doxygen reference manual. This document contains more
technical information about the software internals, development
processes, and similar documentation:

@uref{http://openocd.org/doc/doxygen/html/index.html}

This document is a work-in-progress, but contributions would be welcome
to fill in the gaps. All of the source files are provided in-tree,
listed in the Doxyfile configuration at the top of the source tree.

@section Gerrit Review System

All changes in the OpenOCD Git repository go through the web-based Gerrit
Code Review System:

@uref{https://review.openocd.org/}

After a one-time registration and repository setup, anyone can push commits
from their local Git repository directly into Gerrit.
All users and developers are encouraged to review, test, discuss and vote
for changes in Gerrit. The feedback provides the basis for a maintainer to
eventually submit the change to the main Git repository.

The @file{HACKING} file, also available as the Patch Guide in the Doxygen
Developer Manual, contains basic information about how to connect a
repository to Gerrit, prepare and push patches. Patch authors are expected to
maintain their changes while they're in Gerrit, respond to feedback and if
necessary rework and push improved versions of the change.

@section OpenOCD Developer Mailing List

The OpenOCD Developer Mailing List provides the primary means of
communication between developers:

@uref{https://lists.sourceforge.net/mailman/listinfo/openocd-devel}

@section OpenOCD Bug Tracker

The OpenOCD Bug Tracker is hosted on SourceForge:

@uref{http://bugs.openocd.org/}


@node Debug Adapter Hardware
@chapter Debug Adapter Hardware
@cindex dongles
@cindex FTDI
@cindex wiggler
@cindex printer port
@cindex USB Adapter
@cindex RTCK

Defined: @b{dongle}: A small device that plugs into a computer and serves as
an adapter .... [snip]

In the OpenOCD case, this generally refers to @b{a small adapter} that
attaches to your computer via USB or the parallel port.


@section Choosing a Dongle

There are several things you should keep in mind when choosing a dongle.

@enumerate
@item @b{Transport} Does it support the kind of communication that you need?
OpenOCD focuses mostly on JTAG. Your version may also support
other ways to communicate with target devices.
@item @b{Voltage} What voltage is your target - 1.8, 2.8, 3.3, or 5V?
Does your dongle support it? You might need a level converter.
@item @b{Pinout} What pinout does your target board use?
Does your dongle support it? You may be able to use jumper
wires, or an "octopus" connector, to convert pinouts.
@item @b{Connection} Does your computer have the USB, parallel, or
Ethernet port needed?
@item @b{RTCK} Do you expect to use it with ARM chips and boards with
RTCK support (also known as ``adaptive clocking'')?
@end enumerate

@section USB FT2232 Based

There are many USB JTAG dongles on the market, many of them based
on a chip from ``Future Technology Devices International'' (FTDI)
known as the FTDI FT2232; this is a USB full speed (12 Mbps) chip.
See: @url{http://www.ftdichip.com} for more information.
In summer 2009, USB high speed (480 Mbps) versions of these FTDI
chips started to become available in JTAG adapters. Around 2012, a new
variant appeared - FT232H - this is a single-channel version of FT2232H.
(Adapters using those high speed FT2232H or FT232H chips may support adaptive
clocking.)

The FT2232 chips are flexible enough to support some other
transport options, such as SWD or the SPI variants used to
program some chips. They have two communications channels,
and one can be used for a UART adapter at the same time the
other one is used to provide a debug adapter.

Also, some development boards integrate an FT2232 chip to serve as
a built-in low-cost debug adapter and USB-to-serial solution.

@itemize @bullet
@item @b{usbjtag}
@* Link @url{http://elk.informatik.fh-augsburg.de/hhweb/doc/openocd/usbjtag/usbjtag.html}
@item @b{jtagkey}
@* See: @url{http://www.amontec.com/jtagkey.shtml}
@item @b{jtagkey2}
@* See: @url{http://www.amontec.com/jtagkey2.shtml}
@item @b{oocdlink}
@* See: @url{http://www.oocdlink.com} By Joern Kaipf
@item @b{signalyzer}
@* See: @url{http://www.signalyzer.com}
@item @b{Stellaris Eval Boards}
@* See: @url{http://www.ti.com} - The Stellaris eval boards
bundle FT2232-based JTAG and SWD support, which can be used to debug
the Stellaris chips. Using separate JTAG adapters is optional.
These boards can also be used in a "pass through" mode as JTAG adapters
to other target boards, disabling the Stellaris chip.
@item @b{TI/Luminary ICDI}
@* See: @url{http://www.ti.com} - TI/Luminary In-Circuit Debug
Interface (ICDI) Boards are included in Stellaris LM3S9B9x
Evaluation Kits. Like the non-detachable FT2232 support on the other
Stellaris eval boards, they can be used to debug other target boards.
@item @b{olimex-jtag}
@* See: @url{http://www.olimex.com}
@item @b{Flyswatter/Flyswatter2}
@* See: @url{http://www.tincantools.com}
@item @b{turtelizer2}
@* See:
@uref{http://www.ethernut.de/en/hardware/turtelizer/index.html, Turtelizer 2}, or
@url{http://www.ethernut.de}
@item @b{comstick}
@* Link: @url{http://www.hitex.com/index.php?id=383}
@item @b{stm32stick}
@* Link @url{http://www.hitex.com/stm32-stick}
@item @b{axm0432_jtag}
@* Axiom AXM-0432 Link @url{http://www.axman.com} - NOTE: This JTAG does not appear
to be available anymore as of April 2012.
@item @b{cortino}
@* Link @url{http://www.hitex.com/index.php?id=cortino}
@item @b{dlp-usb1232h}
@* Link @url{http://www.dlpdesign.com/usb/usb1232h.shtml}
@item @b{digilent-hs1}
@* Link @url{http://www.digilentinc.com/Products/Detail.cfm?Prod=JTAG-HS1}
@item @b{opendous}
@* Link @url{http://code.google.com/p/opendous/wiki/JTAG} FT2232H-based
(OpenHardware).
@item @b{JTAG-lock-pick Tiny 2}
@* Link @url{http://www.distortec.com/jtag-lock-pick-tiny-2} FT232H-based

@item @b{GW16042}
@* Link: @url{http://shop.gateworks.com/index.php?route=product/product&path=70_80&product_id=64}
FT2232H-based

@end itemize
@section USB-JTAG / Altera USB-Blaster compatibles

These devices also show up as FTDI devices, but are not
protocol-compatible with the FT2232 devices. They are, however,
protocol-compatible among themselves. USB-JTAG devices typically consist
of a FT245 followed by a CPLD that understands a particular protocol,
or emulates this protocol using some other hardware.

They may appear under different USB VID/PID depending on the particular
product. The driver can be configured to search for any VID/PID pair
(see the section on driver commands).

@itemize
@item @b{USB-JTAG} Kolja Waschk's USB Blaster-compatible adapter
@* Link: @url{http://ixo-jtag.sourceforge.net/}
@item @b{Altera USB-Blaster}
@* Link: @url{http://www.altera.com/literature/ug/ug_usb_blstr.pdf}
@end itemize

@section USB J-Link based
There are several OEM versions of the SEGGER @b{J-Link} adapter. It is
an example of a microcontroller based JTAG adapter, it uses an
AT91SAM764 internally.

@itemize @bullet
@item @b{SEGGER J-Link}
@* Link: @url{http://www.segger.com/jlink.html}
@item @b{Atmel SAM-ICE} (Only works with Atmel chips!)
@* Link: @url{http://www.atmel.com/tools/atmelsam-ice.aspx}
@item @b{IAR J-Link}
@end itemize

@section USB RLINK based
Raisonance has an adapter called @b{RLink}. It exists in a stripped-down form on the STM32 Primer,
permanently attached to the JTAG lines. It also exists on the STM32 Primer2, but that is wired for
SWD and not JTAG, thus not supported.

@itemize @bullet
@item @b{Raisonance RLink}
@* Link: @url{http://www.mcu-raisonance.com/~rlink-debugger-programmer__@/microcontrollers__tool~tool__T018:4cn9ziz4bnx6.html}
@item @b{STM32 Primer}
@* Link: @url{http://www.stm32circle.com/resources/stm32primer.php}
@item @b{STM32 Primer2}
@* Link: @url{http://www.stm32circle.com/resources/stm32primer2.php}
@end itemize

@section USB ST-LINK based
STMicroelectronics has an adapter called @b{ST-LINK}.
They only work with STMicroelectronics chips, notably STM32 and STM8.

@itemize @bullet
@item @b{ST-LINK}
@* This is available standalone and as part of some kits, eg. STM32VLDISCOVERY.
@* Link: @url{http://www.st.com/internet/evalboard/product/219866.jsp}
@item @b{ST-LINK/V2}
@* This is available standalone and as part of some kits, eg. STM32F4DISCOVERY.
@* Link: @url{http://www.st.com/internet/evalboard/product/251168.jsp}
@item @b{STLINK-V3}
@* This is available standalone and as part of some kits.
@* Link: @url{http://www.st.com/stlink-v3}
@end itemize

For info the original ST-LINK enumerates using the mass storage usb class; however,
its implementation is completely broken. The result is this causes issues under Linux.
The simplest solution is to get Linux to ignore the ST-LINK using one of the following methods:
@itemize @bullet
@item modprobe -r usb-storage && modprobe usb-storage quirks=483:3744:i
@item add "options usb-storage quirks=483:3744:i" to /etc/modprobe.conf
@end itemize

@section USB TI/Stellaris ICDI based
Texas Instruments has an adapter called @b{ICDI}.
It is not to be confused with the FTDI based adapters that were originally fitted to their
evaluation boards. This is the adapter fitted to the Stellaris LaunchPad.

@section USB Nuvoton Nu-Link
Nuvoton has an adapter called @b{Nu-Link}.
It is available either as stand-alone dongle and embedded on development boards.
It supports SWD, serial port bridge and mass storage for firmware update.
Both Nu-Link v1 and v2 are supported.

@section USB CMSIS-DAP based
ARM has released a interface standard called CMSIS-DAP that simplifies connecting
debuggers to ARM Cortex based targets @url{http://www.keil.com/support/man/docs/dapdebug/dapdebug_introduction.htm}.

@section USB Other
@itemize @bullet
@item @b{USBprog}
@* Link: @url{http://shop.embedded-projects.net/} - which uses an Atmel MEGA32 and a UBN9604

@item @b{USB - Presto}
@* Link: @url{http://tools.asix.net/prg_presto.htm}

@item @b{Versaloon-Link}
@* Link: @url{http://www.versaloon.com}

@item @b{ARM-JTAG-EW}
@* Link: @url{http://www.olimex.com/dev/arm-jtag-ew.html}

@item @b{Buspirate}
@* Link: @url{http://dangerousprototypes.com/bus-pirate-manual/}

@item @b{opendous}
@* Link: @url{http://code.google.com/p/opendous-jtag/} - which uses an AT90USB162

@item @b{estick}
@* Link: @url{http://code.google.com/p/estick-jtag/}

@item @b{Keil ULINK v1}
@* Link: @url{http://www.keil.com/ulink1/}

@item @b{TI XDS110 Debug Probe}
@* Link: @url{https://software-dl.ti.com/ccs/esd/documents/xdsdebugprobes/emu_xds110.html}
@* Link: @url{https://software-dl.ti.com/ccs/esd/documents/xdsdebugprobes/emu_xds_software_package_download.html#xds110-support-utilities}
@end itemize

@section IBM PC Parallel Printer Port Based

The two well-known ``JTAG Parallel Ports'' cables are the Xilinx DLC5
and the Macraigor Wiggler. There are many clones and variations of
these on the market.

Note that parallel ports are becoming much less common, so if you
have the choice you should probably avoid these adapters in favor
of USB-based ones.

@itemize @bullet

@item @b{Wiggler} - There are many clones of this.
@* Link: @url{http://www.macraigor.com/wiggler.htm}

@item @b{DLC5} - From XILINX - There are many clones of this
@* Link: Search the web for: ``XILINX DLC5'' - it is no longer
produced, PDF schematics are easily found and it is easy to make.

@item @b{Amontec - JTAG Accelerator}
@* Link: @url{http://www.amontec.com/jtag_accelerator.shtml}

@item @b{Wiggler2}
@* Link: @url{http://www.ccac.rwth-aachen.de/~michaels/index.php/hardware/armjtag}

@item @b{Wiggler_ntrst_inverted}
@* Yet another variation - See the source code, src/jtag/parport.c

@item @b{old_amt_wiggler}
@* Unknown - probably not on the market today

@item @b{arm-jtag}
@* Link: Most likely @url{http://www.olimex.com/dev/arm-jtag.html} [another wiggler clone]

@item @b{chameleon}
@* Link: @url{http://www.amontec.com/chameleon.shtml}

@item @b{Triton}
@* Unknown.

@item @b{Lattice}
@* ispDownload from Lattice Semiconductor
@url{http://www.latticesemi.com/lit/docs/@/devtools/dlcable.pdf}

@item @b{flashlink}
@* From STMicroelectronics;
@* Link: @url{http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATA_BRIEF/DM00039500.pdf}

@end itemize

@section Other...
@itemize @bullet

@item @b{ep93xx}
@* An EP93xx based Linux machine using the GPIO pins directly.

@item @b{at91rm9200}
@* Like the EP93xx - but an ATMEL AT91RM9200 based solution using the GPIO pins on the chip.

@item @b{bcm2835gpio}
@* A BCM2835-based board (e.g. Raspberry Pi) using the GPIO pins of the expansion header.

@item @b{imx_gpio}
@* A NXP i.MX-based board (e.g. Wandboard) using the GPIO pins (should work on any i.MX processor).

@item @b{am335xgpio}
@* A Texas Instruments AM335x-based board (e.g. BeagleBone Black) using the GPIO pins of the expansion headers.

@item @b{jtag_vpi}
@* A JTAG driver acting as a client for the JTAG VPI server interface.
@* Link: @url{http://github.com/fjullien/jtag_vpi}

@item @b{vdebug}
@* A driver for Cadence virtual Debug Interface to emulated or simulated targets.
It implements a client connecting to the vdebug server, which in turn communicates
with the emulated or simulated RTL model through a transactor. The current version
supports only JTAG as a transport, but other virtual transports, like DAP are planned.

@item @b{jtag_dpi}
@* A JTAG driver acting as a client for the SystemVerilog Direct Programming
Interface (DPI) for JTAG devices. DPI allows OpenOCD to connect to the JTAG
interface of a hardware model written in SystemVerilog, for example, on an
emulation model of target hardware.

@item @b{xlnx_pcie_xvc}
@* A JTAG driver exposing Xilinx Virtual Cable over PCI Express to OpenOCD as JTAG/SWD interface.

@item @b{linuxgpiod}
@* A bitbang JTAG driver using Linux GPIO through library libgpiod.

@item @b{sysfsgpio}
@* A bitbang JTAG driver using Linux legacy sysfs GPIO.
This is deprecated from Linux v5.3; prefer using @b{linuxgpiod}.

@end itemize

@node About Jim-Tcl
@chapter About Jim-Tcl
@cindex Jim-Tcl
@cindex tcl

OpenOCD uses a small ``Tcl Interpreter'' known as Jim-Tcl.
This programming language provides a simple and extensible
command interpreter.

All commands presented in this Guide are extensions to Jim-Tcl.
You can use them as simple commands, without needing to learn
much of anything about Tcl.
Alternatively, you can write Tcl programs with them.

You can learn more about Jim at its website, @url{http://jim.tcl.tk}.
There is an active and responsive community, get on the mailing list
if you have any questions. Jim-Tcl maintainers also lurk on the
OpenOCD mailing list.

@itemize @bullet
@item @b{Jim vs. Tcl}
@* Jim-Tcl is a stripped down version of the well known Tcl language,
which can be found here: @url{http://www.tcl.tk}. Jim-Tcl has far
fewer features. Jim-Tcl is several dozens of .C files and .H files and
implements the basic Tcl command set. In contrast: Tcl 8.6 is a
4.2 MB .zip file containing 1540 files.

@item @b{Missing Features}
@* Our practice has been: Add/clone the real Tcl feature if/when
needed. We welcome Jim-Tcl improvements, not bloat. Also there
are a large number of optional Jim-Tcl features that are not
enabled in OpenOCD.

@item @b{Scripts}
@* OpenOCD configuration scripts are Jim-Tcl Scripts. OpenOCD's
command interpreter today is a mixture of (newer)
Jim-Tcl commands, and the (older) original command interpreter.

@item @b{Commands}
@* At the OpenOCD telnet command line (or via the GDB monitor command) one
can type a Tcl for() loop, set variables, etc.
Some of the commands documented in this guide are implemented
as Tcl scripts, from a @file{startup.tcl} file internal to the server.

@item @b{Historical Note}
@* Jim-Tcl was introduced to OpenOCD in spring 2008. Fall 2010,
before OpenOCD 0.5 release, OpenOCD switched to using Jim-Tcl
as a Git submodule, which greatly simplified upgrading Jim-Tcl
to benefit from new features and bugfixes in Jim-Tcl.

@item @b{Need a crash course in Tcl?}
@*@xref{Tcl Crash Course}.
@end itemize

@node Running
@chapter Running
@cindex command line options
@cindex logfile
@cindex directory search

Properly installing OpenOCD sets up your operating system to grant it access
to the debug adapters. On Linux, this usually involves installing a file
in @file{/etc/udev/rules.d,} so OpenOCD has permissions. An example rules file
that works for many common adapters is shipped with OpenOCD in the
@file{contrib} directory. MS-Windows needs
complex and confusing driver configuration for every peripheral. Such issues
are unique to each operating system, and are not detailed in this User's Guide.

Then later you will invoke the OpenOCD server, with various options to
tell it how each debug session should work.
The @option{--help} option shows:
@verbatim
bash$ openocd --help

--help       | -h       display this help
--version    | -v       display OpenOCD version
--file       | -f       use configuration file <name>
--search     | -s       dir to search for config files and scripts
--debug      | -d       set debug level to 3
             | -d<n>    set debug level to <level>
--log_output | -l       redirect log output to file <name>
--command    | -c       run <command>
@end verbatim

If you don't give any @option{-f} or @option{-c} options,
OpenOCD tries to read the configuration file @file{openocd.cfg}.
To specify one or more different
configuration files, use @option{-f} options. For example:

@example
openocd -f config1.cfg -f config2.cfg -f config3.cfg
@end example

Configuration files and scripts are searched for in
@enumerate
@item the current directory,
@item any search dir specified on the command line using the @option{-s} option,
@item any search dir specified using the @command{add_script_search_dir} command,
@item a directory in the @env{OPENOCD_SCRIPTS} environment variable (if set),
@item @file{%APPDATA%/OpenOCD} (only on Windows),
@item @file{$HOME/Library/Preferences/org.openocd} (only on Darwin),
@item @file{$XDG_CONFIG_HOME/openocd} (@env{$XDG_CONFIG_HOME} defaults to @file{$HOME/.config}),
@item @file{$HOME/.openocd},
@item the site wide script library @file{$pkgdatadir/site} and
@item the OpenOCD-supplied script library @file{$pkgdatadir/scripts}.
@end enumerate
The first found file with a matching file name will be used.

@quotation Note
Don't try to use configuration script names or paths which
include the "#" character. That character begins Tcl comments.
@end quotation

@section Simple setup, no customization

In the best case, you can use two scripts from one of the script
libraries, hook up your JTAG adapter, and start the server ... and
your JTAG setup will just work "out of the box". Always try to
start by reusing those scripts, but assume you'll need more
customization even if this works. @xref{OpenOCD Project Setup}.

If you find a script for your JTAG adapter, and for your board or
target, you may be able to hook up your JTAG adapter then start
the server with some variation of one of the following:

@example
openocd -f interface/ADAPTER.cfg -f board/MYBOARD.cfg
openocd -f interface/ftdi/ADAPTER.cfg -f board/MYBOARD.cfg
@end example

You might also need to configure which reset signals are present,
using @option{-c 'reset_config trst_and_srst'} or something similar.
If all goes well you'll see output something like

@example
Open On-Chip Debugger 0.4.0 (2010-01-14-15:06)
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : JTAG tap: lm3s.cpu tap/device found: 0x3ba00477
       (mfg: 0x23b, part: 0xba00, ver: 0x3)
@end example

Seeing that "tap/device found" message, and no warnings, means
the JTAG communication is working. That's a key milestone, but
you'll probably need more project-specific setup.

@section What OpenOCD does as it starts

OpenOCD starts by processing the configuration commands provided
on the command line or, if there were no @option{-c command} or
@option{-f file.cfg} options given, in @file{openocd.cfg}.
@xref{configurationstage,,Configuration Stage}.
At the end of the configuration stage it verifies the JTAG scan
chain defined using those commands; your configuration should
ensure that this always succeeds.
Normally, OpenOCD then starts running as a server.
Alternatively, commands may be used to terminate the configuration
stage early, perform work (such as updating some flash memory),
and then shut down without acting as a server.

Once OpenOCD starts running as a server, it waits for connections from
clients (Telnet, GDB, RPC) and processes the commands issued through
those channels.

If you are having problems, you can enable internal debug messages via
the @option{-d} option.

Also it is possible to interleave Jim-Tcl commands w/config scripts using the
@option{-c} command line switch.

To enable debug output (when reporting problems or working on OpenOCD
itself), use the @option{-d} command line switch. This sets the
@option{debug_level} to "3", outputting the most information,
including debug messages. The default setting is "2", outputting only
informational messages, warnings and errors. You can also change this
setting from within a telnet or gdb session using @command{debug_level<n>}
(@pxref{debuglevel,,debug_level}).

You can redirect all output from the server to a file using the
@option{-l <logfile>} switch.

Note! OpenOCD will launch the GDB & telnet server even if it can not
establish a connection with the target. In general, it is possible for
the JTAG controller to be unresponsive until the target is set up
correctly via e.g. GDB monitor commands in a GDB init script.

@node OpenOCD Project Setup
@chapter OpenOCD Project Setup

To use OpenOCD with your development projects, you need to do more than
just connect the JTAG adapter hardware (dongle) to your development board
and start the OpenOCD server.
You also need to configure your OpenOCD server so that it knows
about your adapter and board, and helps your work.
You may also want to connect OpenOCD to GDB, possibly
using Eclipse or some other GUI.

@section Hooking up the JTAG Adapter

Today's most common case is a dongle with a JTAG cable on one side
(such as a ribbon cable with a 10-pin or 20-pin IDC connector)
and a USB cable on the other.
Instead of USB, some dongles use Ethernet;
older ones may use a PC parallel port, or even a serial port.

@enumerate
@item @emph{Start with power to your target board turned off},
and nothing connected to your JTAG adapter.
If you're particularly paranoid, unplug power to the board.
It's important to have the ground signal properly set up,
unless you are using a JTAG adapter which provides
galvanic isolation between the target board and the
debugging host.

@item @emph{Be sure it's the right kind of JTAG connector.}
If your dongle has a 20-pin ARM connector, you need some kind
of adapter (or octopus, see below) to hook it up to
boards using 14-pin or 10-pin connectors ... or to 20-pin
connectors which don't use ARM's pinout.

In the same vein, make sure the voltage levels are compatible.
Not all JTAG adapters have the level shifters needed to work
with 1.2 Volt boards.

@item @emph{Be certain the cable is properly oriented} or you might
damage your board. In most cases there are only two possible
ways to connect the cable.
Connect the JTAG cable from your adapter to the board.
Be sure it's firmly connected.

In the best case, the connector is keyed to physically
prevent you from inserting it wrong.
This is most often done using a slot on the board's male connector
housing, which must match a key on the JTAG cable's female connector.
If there's no housing, then you must look carefully and
make sure pin 1 on the cable hooks up to pin 1 on the board.
Ribbon cables are frequently all grey except for a wire on one
edge, which is red. The red wire is pin 1.

Sometimes dongles provide cables where one end is an ``octopus'' of
color coded single-wire connectors, instead of a connector block.
These are great when converting from one JTAG pinout to another,
but are tedious to set up.
Use these with connector pinout diagrams to help you match up the
adapter signals to the right board pins.

@item @emph{Connect the adapter's other end} once the JTAG cable is connected.
A USB, parallel, or serial port connector will go to the host which
you are using to run OpenOCD.
For Ethernet, consult the documentation and your network administrator.

For USB-based JTAG adapters you have an easy sanity check at this point:
does the host operating system see the JTAG adapter? If you're running
Linux, try the @command{lsusb} command. If that host is an
MS-Windows host, you'll need to install a driver before OpenOCD works.

@item @emph{Connect the adapter's power supply, if needed.}
This step is primarily for non-USB adapters,
but sometimes USB adapters need extra power.

@item @emph{Power up the target board.}
Unless you just let the magic smoke escape,
you're now ready to set up the OpenOCD server
so you can use JTAG to work with that board.

@end enumerate

Talk with the OpenOCD server using
telnet (@code{telnet localhost 4444} on many systems) or GDB.
@xref{GDB and OpenOCD}.

@section Project Directory

There are many ways you can configure OpenOCD and start it up.

A simple way to organize them all involves keeping a
single directory for your work with a given board.
When you start OpenOCD from that directory,
it searches there first for configuration files, scripts,
files accessed through semihosting,
and for code you upload to the target board.
It is also the natural place to write files,
such as log files and data you download from the board.

@section Configuration Basics

There are two basic ways of configuring OpenOCD, and
a variety of ways you can mix them.
Think of the difference as just being how you start the server:

@itemize
@item Many @option{-f file} or @option{-c command} options on the command line
@item No options, but a @dfn{user config file}
in the current directory named @file{openocd.cfg}
@end itemize

Here is an example @file{openocd.cfg} file for a setup
using a Signalyzer FT2232-based JTAG adapter to talk to
a board with an Atmel AT91SAM7X256 microcontroller:

@example
source [find interface/ftdi/signalyzer.cfg]

# GDB can also flash my flash!
gdb_memory_map enable
gdb_flash_program enable

source [find target/sam7x256.cfg]
@end example

Here is the command line equivalent of that configuration:

@example
openocd -f interface/ftdi/signalyzer.cfg \
        -c "gdb_memory_map enable" \
        -c "gdb_flash_program enable" \
        -f target/sam7x256.cfg
@end example

You could wrap such long command lines in shell scripts,
each supporting a different development task.
One might re-flash the board with a specific firmware version.
Another might set up a particular debugging or run-time environment.

@quotation Important
At this writing (October 2009) the command line method has
problems with how it treats variables.
For example, after @option{-c "set VAR value"}, or doing the
same in a script, the variable @var{VAR} will have no value
that can be tested in a later script.
@end quotation

Here we will focus on the simpler solution: one user config
file, including basic configuration plus any TCL procedures
to simplify your work.

@section User Config Files
@cindex config file, user
@cindex user config file
@cindex config file, overview

A user configuration file ties together all the parts of a project
in one place.
One of the following will match your situation best:

@itemize
@item Ideally almost everything comes from configuration files
provided by someone else.
For example, OpenOCD distributes a @file{scripts} directory
(probably in @file{/usr/share/openocd/scripts} on Linux).
Board and tool vendors can provide these too, as can individual
user sites; the @option{-s} command line option lets you say
where to find these files. (@xref{Running}.)
The AT91SAM7X256 example above works this way.

Three main types of non-user configuration file each have their
own subdirectory in the @file{scripts} directory:

@enumerate
@item @b{interface} -- one for each different debug adapter;
@item @b{board} -- one for each different board
@item @b{target} -- the chips which integrate CPUs and other JTAG TAPs
@end enumerate

Best case: include just two files, and they handle everything else.
The first is an interface config file.
The second is board-specific, and it sets up the JTAG TAPs and
their GDB targets (by deferring to some @file{target.cfg} file),
declares all flash memory, and leaves you nothing to do except
meet your deadline:

@example
source [find interface/olimex-jtag-tiny.cfg]
source [find board/csb337.cfg]
@end example

Boards with a single microcontroller often won't need more
than the target config file, as in the AT91SAM7X256 example.
That's because there is no external memory (flash, DDR RAM), and
the board differences are encapsulated by application code.

@item Maybe you don't know yet what your board looks like to JTAG.
Once you know the @file{interface.cfg} file to use, you may
need help from OpenOCD to discover what's on the board.
Once you find the JTAG TAPs, you can just search for appropriate
target and board
configuration files ... or write your own, from the bottom up.
@xref{autoprobing,,Autoprobing}.

@item You can often reuse some standard config files but
need to write a few new ones, probably a @file{board.cfg} file.
You will be using commands described later in this User's Guide,
and working with the guidelines in the next chapter.

For example, there may be configuration files for your JTAG adapter
and target chip, but you need a new board-specific config file
giving access to your particular flash chips.
Or you might need to write another target chip configuration file
for a new chip built around the Cortex-M3 core.

@quotation Note
When you write new configuration files, please submit
them for inclusion in the next OpenOCD release.
For example, a @file{board/newboard.cfg} file will help the
next users of that board, and a @file{target/newcpu.cfg}
will help support users of any board using that chip.
@end quotation

@item
You may need to write some C code.
It may be as simple as supporting a new FT2232 or parport
based adapter; a bit more involved, like a NAND or NOR flash
controller driver; or a big piece of work like supporting
a new chip architecture.
@end itemize

Reuse the existing config files when you can.
Look first in the @file{scripts/boards} area, then @file{scripts/targets}.
You may find a board configuration that's a good example to follow.

When you write config files, separate the reusable parts
(things every user of that interface, chip, or board needs)
from ones specific to your environment and debugging approach.
@itemize

@item
For example, a @code{gdb-attach} event handler that invokes
the @command{reset init} command will interfere with debugging
early boot code, which performs some of the same actions
that the @code{reset-init} event handler does.

@item
Likewise, the @command{arm9 vector_catch} command (or
@cindex vector_catch
its siblings @command{xscale vector_catch}
and @command{cortex_m vector_catch}) can be a time-saver
during some debug sessions, but don't make everyone use that either.
Keep those kinds of debugging aids in your user config file,
along with messaging and tracing setup.
(@xref{softwaredebugmessagesandtracing,,Software Debug Messages and Tracing}.)

@item
You might need to override some defaults.
For example, you might need to move, shrink, or back up the target's
work area if your application needs much SRAM.

@item
TCP/IP port configuration is another example of something which
is environment-specific, and should only appear in
a user config file. @xref{tcpipports,,TCP/IP Ports}.
@end itemize

@section Project-Specific Utilities

A few project-specific utility
routines may well speed up your work.
Write them, and keep them in your project's user config file.

For example, if you are making a boot loader work on a
board, it's nice to be able to debug the ``after it's
loaded to RAM'' parts separately from the finicky early
code which sets up the DDR RAM controller and clocks.
A script like this one, or a more GDB-aware sibling,
may help:

@example
proc ramboot @{ @} @{
    # Reset, running the target's "reset-init" scripts
    # to initialize clocks and the DDR RAM controller.
    # Leave the CPU halted.
    reset init

    # Load CONFIG_SKIP_LOWLEVEL_INIT version into DDR RAM.
    load_image u-boot.bin 0x20000000

    # Start running.
    resume 0x20000000
@}
@end example

Then once that code is working you will need to make it
boot from NOR flash; a different utility would help.
Alternatively, some developers write to flash using GDB.
(You might use a similar script if you're working with a flash
based microcontroller application instead of a boot loader.)

@example
proc newboot @{ @} @{
    # Reset, leaving the CPU halted. The "reset-init" event
    # proc gives faster access to the CPU and to NOR flash;
    # "reset halt" would be slower.
    reset init

    # Write standard version of U-Boot into the first two
    # sectors of NOR flash ... the standard version should
    # do the same lowlevel init as "reset-init".
    flash protect 0 0 1 off
    flash erase_sector 0 0 1
    flash write_bank 0 u-boot.bin 0x0
    flash protect 0 0 1 on

    # Reboot from scratch using that new boot loader.
    reset run
@}
@end example

You may need more complicated utility procedures when booting
from NAND.
That often involves an extra bootloader stage,
running from on-chip SRAM to perform DDR RAM setup so it can load
the main bootloader code (which won't fit into that SRAM).

Other helper scripts might be used to write production system images,
involving considerably more than just a three stage bootloader.

@section Target Software Changes

Sometimes you may want to make some small changes to the software
you're developing, to help make JTAG debugging work better.
For example, in C or assembly language code you might
use @code{#ifdef JTAG_DEBUG} (or its converse) around code
handling issues like:

@itemize @bullet

@item @b{Watchdog Timers}...
Watchdog timers are typically used to automatically reset systems if
some application task doesn't periodically reset the timer. (The
assumption is that the system has locked up if the task can't run.)
When a JTAG debugger halts the system, that task won't be able to run
and reset the timer ... potentially causing resets in the middle of
your debug sessions.

It's rarely a good idea to disable such watchdogs, since their usage
needs to be debugged just like all other parts of your firmware.
That might however be your only option.

Look instead for chip-specific ways to stop the watchdog from counting
while the system is in a debug halt state. It may be simplest to set
that non-counting mode in your debugger startup scripts. You may however
need a different approach when, for example, a motor could be physically
damaged by firmware remaining inactive in a debug halt state. That might
involve a type of firmware mode where that "non-counting" mode is disabled
at the beginning then re-enabled at the end; a watchdog reset might fire
and complicate the debug session, but hardware (or people) would be
protected.@footnote{Note that many systems support a "monitor mode" debug
that is a somewhat cleaner way to address such issues. You can think of
it as only halting part of the system, maybe just one task,
instead of the whole thing.
At this writing, January 2010, OpenOCD based debugging does not support
monitor mode debug, only "halt mode" debug.}

@item @b{ARM Semihosting}...
@cindex ARM semihosting
When linked with a special runtime library provided with many
toolchains@footnote{See chapter 8 "Semihosting" in
@uref{http://infocenter.arm.com/help/topic/com.arm.doc.dui0203i/DUI0203I_rvct_developer_guide.pdf,
ARM DUI 0203I}, the "RealView Compilation Tools Developer Guide".
The CodeSourcery EABI toolchain also includes a semihosting library.},
your target code can use I/O facilities on the debug host. That library
provides a small set of system calls which are handled by OpenOCD.
It can let the debugger provide your system console and a file system,
helping with early debugging or providing a more capable environment
for sometimes-complex tasks like installing system firmware onto
NAND or SPI flash.

@item @b{ARM Wait-For-Interrupt}...
Many ARM chips synchronize the JTAG clock using the core clock.
Low power states which stop that core clock thus prevent JTAG access.
Idle loops in tasking environments often enter those low power states
via the @code{WFI} instruction (or its coprocessor equivalent, before ARMv7).

You may want to @emph{disable that instruction} in source code,
or otherwise prevent using that state,
to ensure you can get JTAG access at any time.@footnote{As a more
polite alternative, some processors have special debug-oriented
registers which can be used to change various features including
how the low power states are clocked while debugging.
The STM32 DBGMCU_CR register is an example; at the cost of extra
power consumption, JTAG can be used during low power states.}
For example, the OpenOCD @command{halt} command may not
work for an idle processor otherwise.

@item @b{Delay after reset}...
Not all chips have good support for debugger access
right after reset; many LPC2xxx chips have issues here.
Similarly, applications that reconfigure pins used for
JTAG access as they start will also block debugger access.

To work with boards like this, @emph{enable a short delay loop}
the first thing after reset, before "real" startup activities.
For example, one second's delay is usually more than enough
time for a JTAG debugger to attach, so that
early code execution can be debugged
or firmware can be replaced.

@item @b{Debug Communications Channel (DCC)}...
Some processors include mechanisms to send messages over JTAG.
Many ARM cores support these, as do some cores from other vendors.
(OpenOCD may be able to use this DCC internally, speeding up some
operations like writing to memory.)

Your application may want to deliver various debugging messages
over JTAG, by @emph{linking with a small library of code}
provided with OpenOCD and using the utilities there to send
various kinds of message.
@xref{softwaredebugmessagesandtracing,,Software Debug Messages and Tracing}.

@end itemize

@section Target Hardware Setup

Chip vendors often provide software development boards which
are highly configurable, so that they can support all options
that product boards may require. @emph{Make sure that any
jumpers or switches match the system configuration you are
working with.}

Common issues include:

@itemize @bullet

@item @b{JTAG setup} ...
Boards may support more than one JTAG configuration.
Examples include jumpers controlling pullups versus pulldowns
on the nTRST and/or nSRST signals, and choice of connectors
(e.g. which of two headers on the base board,
or one from a daughtercard).
For some Texas Instruments boards, you may need to jumper the
EMU0 and EMU1 signals (which OpenOCD won't currently control).

@item @b{Boot Modes} ...
Complex chips often support multiple boot modes, controlled
by external jumpers. Make sure this is set up correctly.
For example many i.MX boards from NXP need to be jumpered
to "ATX mode" to start booting using the on-chip ROM, when
using second stage bootloader code stored in a NAND flash chip.

Such explicit configuration is common, and not limited to
booting from NAND. You might also need to set jumpers to
start booting using code loaded from an MMC/SD card; external
SPI flash; Ethernet, UART, or USB links; NOR flash; OneNAND
flash; some external host; or various other sources.


@item @b{Memory Addressing} ...
Boards which support multiple boot modes may also have jumpers
to configure memory addressing. One board, for example, jumpers
external chipselect 0 (used for booting) to address either
a large SRAM (which must be pre-loaded via JTAG), NOR flash,
or NAND flash. When it's jumpered to address NAND flash, that
board must also be told to start booting from on-chip ROM.

Your @file{board.cfg} file may also need to be told this jumper
configuration, so that it can know whether to declare NOR flash
using @command{flash bank} or instead declare NAND flash with
@command{nand device}; and likewise which probe to perform in
its @code{reset-init} handler.

A closely related issue is bus width. Jumpers might need to
distinguish between 8 bit or 16 bit bus access for the flash
used to start booting.

@item @b{Peripheral Access} ...
Development boards generally provide access to every peripheral
on the chip, sometimes in multiple modes (such as by providing
multiple audio codec chips).
This interacts with software
configuration of pin multiplexing, where for example a
given pin may be routed either to the MMC/SD controller
or the GPIO controller. It also often interacts with
configuration jumpers. One jumper may be used to route
signals to an MMC/SD card slot or an expansion bus (which
might in turn affect booting); others might control which
audio or video codecs are used.

@end itemize

Plus you should of course have @code{reset-init} event handlers
which set up the hardware to match that jumper configuration.
That includes in particular any oscillator or PLL used to clock
the CPU, and any memory controllers needed to access external
memory and peripherals. Without such handlers, you won't be
able to access those resources without working target firmware
which can do that setup ... this can be awkward when you're
trying to debug that target firmware. Even if there's a ROM
bootloader which handles a few issues, it rarely provides full
access to all board-specific capabilities.


@node Config File Guidelines
@chapter Config File Guidelines

This chapter is aimed at any user who needs to write a config file,
including developers and integrators of OpenOCD and any user who
needs to get a new board working smoothly.
It provides guidelines for creating those files.

You should find the following directories under
@t{$(INSTALLDIR)/scripts}, with config files maintained upstream. Use
them as-is where you can; or as models for new files.
@itemize @bullet
@item @file{interface} ...
These are for debug adapters. Files that specify configuration to use
specific JTAG, SWD and other adapters go here.
@item @file{board} ...
Think Circuit Board, PWA, PCB, they go by many names. Board files
contain initialization items that are specific to a board.

They reuse target configuration files, since the same
microprocessor chips are used on many boards,
but support for external parts varies widely. For
example, the SDRAM initialization sequence for the board, or the type
of external flash and what address it uses. Any initialization
sequence to enable that external flash or SDRAM should be found in the
board file. Boards may also contain multiple targets: two CPUs; or
a CPU and an FPGA.
@item @file{target} ...
Think chip. The ``target'' directory represents the JTAG TAPs
on a chip
which OpenOCD should control, not a board. Two common types of targets
are ARM chips and FPGA or CPLD chips.
When a chip has multiple TAPs (maybe it has both ARM and DSP cores),
the target config file defines all of them.
@item @emph{more} ... browse for other library files which may be useful.
For example, there are various generic and CPU-specific utilities.
@end itemize

The @file{openocd.cfg} user config
file may override features in any of the above files by
setting variables before sourcing the target file, or by adding
commands specific to their situation.

@section Interface Config Files

The user config file
should be able to source one of these files with a command like this:

@example
source [find interface/FOOBAR.cfg]
@end example

A preconfigured interface file should exist for every debug adapter
in use today with OpenOCD.
That said, perhaps some of these config files
have only been used by the developer who created it.

A separate chapter gives information about how to set these up.
@xref{Debug Adapter Configuration}.
Read the OpenOCD source code (and Developer's Guide)
if you have a new kind of hardware interface
and need to provide a driver for it.

@deffn {Command} {find} 'filename'
Prints full path to @var{filename} according to OpenOCD search rules.
@end deffn

@deffn {Command} {ocd_find} 'filename'
Prints full path to @var{filename} according to OpenOCD search rules. This
is a low level function used by the @command{find}. Usually you want
to use @command{find}, instead.
@end deffn

@section Board Config Files
@cindex config file, board
@cindex board config file

The user config file
should be able to source one of these files with a command like this:

@example
source [find board/FOOBAR.cfg]
@end example

The point of a board config file is to package everything
about a given board that user config files need to know.
In summary the board files should contain (if present)

@enumerate
@item One or more @command{source [find target/...cfg]} statements
@item NOR flash configuration (@pxref{norconfiguration,,NOR Configuration})
@item NAND flash configuration (@pxref{nandconfiguration,,NAND Configuration})
@item Target @code{reset} handlers for SDRAM and I/O configuration
@item JTAG adapter reset configuration (@pxref{Reset Configuration})
@item All things that are not ``inside a chip''
@end enumerate

Generic things inside target chips belong in target config files,
not board config files. So for example a @code{reset-init} event
handler should know board-specific oscillator and PLL parameters,
which it passes to target-specific utility code.

The most complex task of a board config file is creating such a
@code{reset-init} event handler.
Define those handlers last, after you verify the rest of the board
configuration works.

@subsection Communication Between Config files

In addition to target-specific utility code, another way that
board and target config files communicate is by following a
convention on how to use certain variables.

The full Tcl/Tk language supports ``namespaces'', but Jim-Tcl does not.
Thus the rule we follow in OpenOCD is this: Variables that begin with
a leading underscore are temporary in nature, and can be modified and
used at will within a target configuration file.

Complex board config files can do the things like this,
for a board with three chips:

@example
# Chip #1: PXA270 for network side, big endian
set CHIPNAME network
set ENDIAN big
source [find target/pxa270.cfg]
# on return: _TARGETNAME = network.cpu
# other commands can refer to the "network.cpu" target.
$_TARGETNAME configure .... events for this CPU..

# Chip #2: PXA270 for video side, little endian
set CHIPNAME video
set ENDIAN little
source [find target/pxa270.cfg]
# on return: _TARGETNAME = video.cpu
# other commands can refer to the "video.cpu" target.
$_TARGETNAME configure .... events for this CPU..

# Chip #3: Xilinx FPGA for glue logic
set CHIPNAME xilinx
unset ENDIAN
source [find target/spartan3.cfg]
@end example

That example is oversimplified because it doesn't show any flash memory,
or the @code{reset-init} event handlers to initialize external DRAM
or (assuming it needs it) load a configuration into the FPGA.
Such features are usually needed for low-level work with many boards,
where ``low level'' implies that the board initialization software may
not be working. (That's a common reason to need JTAG tools. Another
is to enable working with microcontroller-based systems, which often
have no debugging support except a JTAG connector.)

Target config files may also export utility functions to board and user
config files. Such functions should use name prefixes, to help avoid
naming collisions.

Board files could also accept input variables from user config files.
For example, there might be a @code{J4_JUMPER} setting used to identify
what kind of flash memory a development board is using, or how to set
up other clocks and peripherals.

@subsection Variable Naming Convention
@cindex variable names

Most boards have only one instance of a chip.
However, it should be easy to create a board with more than
one such chip (as shown above).
Accordingly, we encourage these conventions for naming
variables associated with different @file{target.cfg} files,
to promote consistency and
so that board files can override target defaults.

Inputs to target config files include:

@itemize @bullet
@item @code{CHIPNAME} ...
This gives a name to the overall chip, and is used as part of
tap identifier dotted names.
While the default is normally provided by the chip manufacturer,
board files may need to distinguish between instances of a chip.
@item @code{ENDIAN} ...
By default @option{little} - although chips may hard-wire @option{big}.
Chips that can't change endianness don't need to use this variable.
@item @code{CPUTAPID} ...
When OpenOCD examines the JTAG chain, it can be told verify the
chips against the JTAG IDCODE register.
The target file will hold one or more defaults, but sometimes the
chip in a board will use a different ID (perhaps a newer revision).
@end itemize

Outputs from target config files include:

@itemize @bullet
@item @code{_TARGETNAME} ...
By convention, this variable is created by the target configuration
script. The board configuration file may make use of this variable to
configure things like a ``reset init'' script, or other things
specific to that board and that target.
If the chip has 2 targets, the names are @code{_TARGETNAME0},
@code{_TARGETNAME1}, ... etc.
@end itemize

@subsection The reset-init Event Handler
@cindex event, reset-init
@cindex reset-init handler

Board config files run in the OpenOCD configuration stage;
they can't use TAPs or targets, since they haven't been
fully set up yet.
This means you can't write memory or access chip registers;
you can't even verify that a flash chip is present.
That's done later in event handlers, of which the target @code{reset-init}
handler is one of the most important.

Except on microcontrollers, the basic job of @code{reset-init} event
handlers is setting up flash and DRAM, as normally handled by boot loaders.
Microcontrollers rarely use boot loaders; they run right out of their
on-chip flash and SRAM memory. But they may want to use one of these
handlers too, if just for developer convenience.

@quotation Note
Because this is so very board-specific, and chip-specific, no examples
are included here.
Instead, look at the board config files distributed with OpenOCD.
If you have a boot loader, its source code will help; so will
configuration files for other JTAG tools
(@pxref{translatingconfigurationfiles,,Translating Configuration Files}).
@end quotation

Some of this code could probably be shared between different boards.
For example, setting up a DRAM controller often doesn't differ by
much except the bus width (16 bits or 32?) and memory timings, so a
reusable TCL procedure loaded by the @file{target.cfg} file might take
those as parameters.
Similarly with oscillator, PLL, and clock setup;
and disabling the watchdog.
Structure the code cleanly, and provide comments to help
the next developer doing such work.
(@emph{You might be that next person} trying to reuse init code!)

The last thing normally done in a @code{reset-init} handler is probing
whatever flash memory was configured. For most chips that needs to be
done while the associated target is halted, either because JTAG memory
access uses the CPU or to prevent conflicting CPU access.

@subsection JTAG Clock Rate

Before your @code{reset-init} handler has set up
the PLLs and clocking, you may need to run with
a low JTAG clock rate.
@xref{jtagspeed,,JTAG Speed}.
Then you'd increase that rate after your handler has
made it possible to use the faster JTAG clock.
When the initial low speed is board-specific, for example
because it depends on a board-specific oscillator speed, then
you should probably set it up in the board config file;
if it's target-specific, it belongs in the target config file.

For most ARM-based processors the fastest JTAG clock@footnote{A FAQ
@uref{http://www.arm.com/support/faqdev/4170.html} gives details.}
is one sixth of the CPU clock; or one eighth for ARM11 cores.
Consult chip documentation to determine the peak JTAG clock rate,
which might be less than that.

@quotation Warning
On most ARMs, JTAG clock detection is coupled to the core clock, so
software using a @option{wait for interrupt} operation blocks JTAG access.
Adaptive clocking provides a partial workaround, but a more complete
solution just avoids using that instruction with JTAG debuggers.
@end quotation

If both the chip and the board support adaptive clocking,
use the @command{jtag_rclk}
command, in case your board is used with JTAG adapter which
also supports it. Otherwise use @command{adapter speed}.
Set the slow rate at the beginning of the reset sequence,
and the faster rate as soon as the clocks are at full speed.

@anchor{theinitboardprocedure}
@subsection The init_board procedure
@cindex init_board procedure

The concept of @code{init_board} procedure is very similar to @code{init_targets}
(@xref{theinittargetsprocedure,,The init_targets procedure}.) - it's a replacement of ``linear''
configuration scripts. This procedure is meant to be executed when OpenOCD enters run stage
(@xref{enteringtherunstage,,Entering the Run Stage},) after @code{init_targets}. The idea to have
separate @code{init_targets} and @code{init_board} procedures is to allow the first one to configure
everything target specific (internal flash, internal RAM, etc.) and the second one to configure
everything board specific (reset signals, chip frequency, reset-init event handler, external memory, etc.).
Additionally ``linear'' board config file will most likely fail when target config file uses
@code{init_targets} scheme (``linear'' script is executed before @code{init} and @code{init_targets} - after),
so separating these two configuration stages is very convenient, as the easiest way to overcome this
problem is to convert board config file to use @code{init_board} procedure. Board config scripts don't
need to override @code{init_targets} defined in target config files when they only need to add some specifics.

Just as @code{init_targets}, the @code{init_board} procedure can be overridden by ``next level'' script (which sources
the original), allowing greater code reuse.

@example
### board_file.cfg ###

# source target file that does most of the config in init_targets
source [find target/target.cfg]

proc enable_fast_clock @{@} @{
    # enables fast on-board clock source
    # configures the chip to use it
@}

# initialize only board specifics - reset, clock, adapter frequency
proc init_board @{@} @{
    reset_config trst_and_srst trst_pulls_srst

    $_TARGETNAME configure -event reset-start @{
        adapter speed 100
    @}

    $_TARGETNAME configure -event reset-init @{
        enable_fast_clock
        adapter speed 10000
    @}
@}
@end example

@section Target Config Files
@cindex config file, target
@cindex target config file

Board config files communicate with target config files using
naming conventions as described above, and may source one or
more target config files like this:

@example
source [find target/FOOBAR.cfg]
@end example

The point of a target config file is to package everything
about a given chip that board config files need to know.
In summary the target files should contain

@enumerate
@item Set defaults
@item Add TAPs to the scan chain
@item Add CPU targets (includes GDB support)
@item CPU/Chip/CPU-Core specific features
@item On-Chip flash
@end enumerate

As a rule of thumb, a target file sets up only one chip.
For a microcontroller, that will often include a single TAP,
which is a CPU needing a GDB target, and its on-chip flash.

More complex chips may include multiple TAPs, and the target
config file may need to define them all before OpenOCD
can talk to the chip.
For example, some phone chips have JTAG scan chains that include
an ARM core for operating system use, a DSP,
another ARM core embedded in an image processing engine,
and other processing engines.

@subsection Default Value Boiler Plate Code

All target configuration files should start with code like this,
letting board config files express environment-specific
differences in how things should be set up.

@example
# Boards may override chip names, perhaps based on role,
# but the default should match what the vendor uses
if @{ [info exists CHIPNAME] @} @{
   set  _CHIPNAME $CHIPNAME
@} else @{
   set  _CHIPNAME sam7x256
@}

# ONLY use ENDIAN with targets that can change it.
if @{ [info exists ENDIAN] @} @{
   set  _ENDIAN $ENDIAN
@} else @{
   set  _ENDIAN little
@}

# TAP identifiers may change as chips mature, for example with
# new revision fields (the "3" here). Pick a good default; you
# can pass several such identifiers to the "jtag newtap" command.
if @{ [info exists CPUTAPID ] @} @{
   set _CPUTAPID $CPUTAPID
@} else @{
   set _CPUTAPID 0x3f0f0f0f
@}
@end example
@c but 0x3f0f0f0f is for an str73x part ...

@emph{Remember:} Board config files may include multiple target
config files, or the same target file multiple times
(changing at least @code{CHIPNAME}).

Likewise, the target configuration file should define
@code{_TARGETNAME} (or @code{_TARGETNAME0} etc) and
use it later on when defining debug targets:

@example
set _TARGETNAME $_CHIPNAME.cpu
target create $_TARGETNAME arm7tdmi -chain-position $_TARGETNAME
@end example

@subsection Adding TAPs to the Scan Chain
After the ``defaults'' are set up,
add the TAPs on each chip to the JTAG scan chain.
@xref{TAP Declaration}, and the naming convention
for taps.

In the simplest case the chip has only one TAP,
probably for a CPU or FPGA.
The config file for the Atmel AT91SAM7X256
looks (in part) like this:

@example
jtag newtap $_CHIPNAME cpu -irlen 4 -expected-id $_CPUTAPID
@end example

A board with two such at91sam7 chips would be able
to source such a config file twice, with different
values for @code{CHIPNAME}, so
it adds a different TAP each time.

If there are nonzero @option{-expected-id} values,
OpenOCD attempts to verify the actual tap id against those values.
It will issue error messages if there is mismatch, which
can help to pinpoint problems in OpenOCD configurations.

@example
JTAG tap: sam7x256.cpu tap/device found: 0x3f0f0f0f
                (Manufacturer: 0x787, Part: 0xf0f0, Version: 0x3)
ERROR: Tap: sam7x256.cpu - Expected id: 0x12345678, Got: 0x3f0f0f0f
ERROR: expected: mfg: 0x33c, part: 0x2345, ver: 0x1
ERROR:      got: mfg: 0x787, part: 0xf0f0, ver: 0x3
@end example

There are more complex examples too, with chips that have
multiple TAPs. Ones worth looking at include:

@itemize
@item @file{target/omap3530.cfg} -- with disabled ARM and DSP,
plus a JRC to enable them
@item @file{target/str912.cfg} -- with flash, CPU, and boundary scan
@item @file{target/ti_dm355.cfg} -- with ETM, ARM, and JRC (this JRC
is not currently used)
@end itemize

@subsection Add CPU targets

After adding a TAP for a CPU, you should set it up so that
GDB and other commands can use it.
@xref{CPU Configuration}.
For the at91sam7 example above, the command can look like this;
note that @code{$_ENDIAN} is not needed, since OpenOCD defaults
to little endian, and this chip doesn't support changing that.

@example
set _TARGETNAME $_CHIPNAME.cpu
target create $_TARGETNAME arm7tdmi -chain-position $_TARGETNAME
@end example

Work areas are small RAM areas associated with CPU targets.
They are used by OpenOCD to speed up downloads,
and to download small snippets of code to program flash chips.
If the chip includes a form of ``on-chip-ram'' - and many do - define
a work area if you can.
Again using the at91sam7 as an example, this can look like:

@example
$_TARGETNAME configure -work-area-phys 0x00200000 \
             -work-area-size 0x4000 -work-area-backup 0
@end example

@anchor{definecputargetsworkinginsmp}
@subsection Define CPU targets working in SMP
@cindex SMP
After setting targets, you can define a list of targets working in SMP.

@example
set _TARGETNAME_1 $_CHIPNAME.cpu1
set _TARGETNAME_2 $_CHIPNAME.cpu2
target create $_TARGETNAME_1 cortex_a -chain-position $_CHIPNAME.dap \
-coreid 0 -dbgbase $_DAP_DBG1
target create $_TARGETNAME_2 cortex_a -chain-position $_CHIPNAME.dap \
-coreid 1 -dbgbase $_DAP_DBG2
#define 2 targets working in smp.
target smp $_CHIPNAME.cpu2 $_CHIPNAME.cpu1
@end example
In the above example on cortex_a, 2 cpus are working in SMP.
In SMP only one GDB instance is created and :
@itemize @bullet
@item a set of hardware breakpoint sets the same breakpoint on all targets in the list.
@item halt command triggers the halt of all targets in the list.
@item resume command triggers the write context and the restart of all targets in the list.
@item following a breakpoint: the target stopped by the breakpoint is displayed to the GDB session.
@item dedicated GDB serial protocol packets are implemented for switching/retrieving the target
displayed by the GDB session @pxref{usingopenocdsmpwithgdb,,Using OpenOCD SMP with GDB}.
@end itemize

The SMP behaviour can be disabled/enabled dynamically. On cortex_a following
command have been implemented.
@itemize @bullet
@item cortex_a smp on : enable SMP mode, behaviour is as described above.
@item cortex_a smp off : disable SMP mode, the current target is the one
displayed in the GDB session, only this target is now controlled by GDB
session. This behaviour is useful during system boot up.
@item cortex_a smp : display current SMP mode.
@item cortex_a smp_gdb : display/fix the core id displayed in GDB session see
following example.
@end itemize

@example
>cortex_a smp_gdb
gdb coreid  0 -> -1
#0 : coreid 0 is displayed to GDB ,
#-> -1 : next resume triggers a real resume
> cortex_a smp_gdb 1
gdb coreid  0 -> 1
#0 :coreid 0 is displayed to GDB ,
#->1  : next resume displays coreid 1 to GDB
> resume
> cortex_a smp_gdb
gdb coreid  1 -> 1
#1 :coreid 1 is displayed to GDB ,
#->1 : next resume displays coreid 1 to GDB
> cortex_a smp_gdb -1
gdb coreid  1 -> -1
#1 :coreid 1 is displayed to GDB,
#->-1 : next resume triggers a real resume
@end example


@subsection Chip Reset Setup

As a rule, you should put the @command{reset_config} command
into the board file. Most things you think you know about a
chip can be tweaked by the board.

Some chips have specific ways the TRST and SRST signals are
managed. In the unusual case that these are @emph{chip specific}
and can never be changed by board wiring, they could go here.
For example, some chips can't support JTAG debugging without
both signals.

Provide a @code{reset-assert} event handler if you can.
Such a handler uses JTAG operations to reset the target,
letting this target config be used in systems which don't
provide the optional SRST signal, or on systems where you
don't want to reset all targets at once.
Such a handler might write to chip registers to force a reset,
use a JRC to do that (preferable -- the target may be wedged!),
or force a watchdog timer to trigger.
(For Cortex-M targets, this is not necessary.  The target
driver knows how to use trigger an NVIC reset when SRST is
not available.)

Some chips need special attention during reset handling if
they're going to be used with JTAG.
An example might be needing to send some commands right
after the target's TAP has been reset, providing a
@code{reset-deassert-post} event handler that writes a chip
register to report that JTAG debugging is being done.
Another would be reconfiguring the watchdog so that it stops
counting while the core is halted in the debugger.

JTAG clocking constraints often change during reset, and in
some cases target config files (rather than board config files)
are the right places to handle some of those issues.
For example, immediately after reset most chips run using a
slower clock than they will use later.
That means that after reset (and potentially, as OpenOCD
first starts up) they must use a slower JTAG clock rate
than they will use later.
@xref{jtagspeed,,JTAG Speed}.

@quotation Important
When you are debugging code that runs right after chip
reset, getting these issues right is critical.
In particular, if you see intermittent failures when
OpenOCD verifies the scan chain after reset,
look at how you are setting up JTAG clocking.
@end quotation

@anchor{theinittargetsprocedure}
@subsection The init_targets procedure
@cindex init_targets procedure

Target config files can either be ``linear'' (script executed line-by-line when parsed in
configuration stage, @xref{configurationstage,,Configuration Stage},) or they can contain a special
procedure called @code{init_targets}, which will be executed when entering run stage
(after parsing all config files or after @code{init} command, @xref{enteringtherunstage,,Entering the Run Stage}.)
Such procedure can be overridden by ``next level'' script (which sources the original).
This concept facilitates code reuse when basic target config files provide generic configuration
procedures and @code{init_targets} procedure, which can then be sourced and enhanced or changed in
a ``more specific'' target config file. This is not possible with ``linear'' config scripts,
because sourcing them executes every initialization commands they provide.

@example
### generic_file.cfg ###

proc setup_my_chip @{chip_name flash_size ram_size@} @{
    # basic initialization procedure ...
@}

proc init_targets @{@} @{
    # initializes generic chip with 4kB of flash and 1kB of RAM
    setup_my_chip MY_GENERIC_CHIP 4096 1024
@}

### specific_file.cfg ###

source [find target/generic_file.cfg]

proc init_targets @{@} @{
    # initializes specific chip with 128kB of flash and 64kB of RAM
    setup_my_chip MY_CHIP_WITH_128K_FLASH_64KB_RAM 131072 65536
@}
@end example

The easiest way to convert ``linear'' config files to @code{init_targets} version is to
enclose every line of ``code'' (i.e. not @code{source} commands, procedures, etc.) in this procedure.

For an example of this scheme see LPC2000 target config files.

The @code{init_boards} procedure is a similar concept concerning board config files
(@xref{theinitboardprocedure,,The init_board procedure}.)

@anchor{theinittargeteventsprocedure}
@subsection The init_target_events procedure
@cindex init_target_events procedure

A special procedure called @code{init_target_events} is run just after
@code{init_targets} (@xref{theinittargetsprocedure,,The init_targets
procedure}.) and before @code{init_board}
(@xref{theinitboardprocedure,,The init_board procedure}.) It is used
to set up default target events for the targets that do not have those
events already assigned.

@subsection ARM Core Specific Hacks

If the chip has a DCC, enable it. If the chip is an ARM9 with some
special high speed download features - enable it.

If present, the MMU, the MPU and the CACHE should be disabled.

Some ARM cores are equipped with trace support, which permits
examination of the instruction and data bus activity. Trace
activity is controlled through an ``Embedded Trace Module'' (ETM)
on one of the core's scan chains. The ETM emits voluminous data
through a ``trace port''. (@xref{armhardwaretracing,,ARM Hardware Tracing}.)
If you are using an external trace port,
configure it in your board config file.
If you are using an on-chip ``Embedded Trace Buffer'' (ETB),
configure it in your target config file.

@example
etm config $_TARGETNAME 16 normal full etb
etb config $_TARGETNAME $_CHIPNAME.etb
@end example

@subsection Internal Flash Configuration

This applies @b{ONLY TO MICROCONTROLLERS} that have flash built in.

@b{Never ever} in the ``target configuration file'' define any type of
flash that is external to the chip. (For example a BOOT flash on
Chip Select 0.) Such flash information goes in a board file - not
the TARGET (chip) file.

Examples:
@itemize @bullet
@item at91sam7x256 - has 256K flash YES enable it.
@item str912 - has flash internal YES enable it.
@item imx27 - uses boot flash on CS0 - it goes in the board file.
@item pxa270 - again - CS0 flash - it goes in the board file.
@end itemize

@anchor{translatingconfigurationfiles}
@section Translating Configuration Files
@cindex translation
If you have a configuration file for another hardware debugger
or toolset (Abatron, BDI2000, BDI3000, CCS,
Lauterbach, SEGGER, Macraigor, etc.), translating
it into OpenOCD syntax is often quite straightforward. The most tricky
part of creating a configuration script is oftentimes the reset init
sequence where e.g. PLLs, DRAM and the like is set up.

One trick that you can use when translating is to write small
Tcl procedures to translate the syntax into OpenOCD syntax. This
can avoid manual translation errors and make it easier to
convert other scripts later on.

Example of transforming quirky arguments to a simple search and
replace job:

@example
#   Lauterbach syntax(?)
#
#       Data.Set c15:0x042f %long 0x40000015
#
#   OpenOCD syntax when using procedure below.
#
#       setc15 0x01 0x00050078

proc setc15 @{regs value@} @{
    global TARGETNAME

    echo [format "set p15 0x%04x, 0x%08x" $regs $value]

    arm mcr 15 [expr @{($regs >> 12) & 0x7@}] \
        [expr @{($regs >> 0) & 0xf@}] [expr @{($regs >> 4) & 0xf@}] \
        [expr @{($regs >> 8) & 0x7@}] $value
@}
@end example



@node Server Configuration
@chapter Server Configuration
@cindex initialization
The commands here are commonly found in the openocd.cfg file and are
used to specify what TCP/IP ports are used, and how GDB should be
supported.

@anchor{configurationstage}
@section Configuration Stage
@cindex configuration stage
@cindex config command

When the OpenOCD server process starts up, it enters a
@emph{configuration stage} which is the only time that
certain commands, @emph{configuration commands}, may be issued.
Normally, configuration commands are only available
inside startup scripts.

In this manual, the definition of a configuration command is
presented as a @emph{Config Command}, not as a @emph{Command}
which may be issued interactively.
The runtime @command{help} command also highlights configuration
commands, and those which may be issued at any time.

Those configuration commands include declaration of TAPs,
flash banks,
the interface used for JTAG communication,
and other basic setup.
The server must leave the configuration stage before it
may access or activate TAPs.
After it leaves this stage, configuration commands may no
longer be issued.

@deffn {Command} {command mode} [command_name]
Returns the command modes allowed by a command: 'any', 'config', or
'exec'. If no command is specified, returns the current command
mode. Returns 'unknown' if an unknown command is given. Command can be
multiple tokens. (command valid any time)

In this document, the modes are described as stages, 'config' and
'exec' mode correspond configuration stage and run stage. 'any' means
the command can be executed in either
stages. @xref{configurationstage,,Configuration Stage}, and
@xref{enteringtherunstage,,Entering the Run Stage}.
@end deffn

@anchor{enteringtherunstage}
@section Entering the Run Stage

The first thing OpenOCD does after leaving the configuration
stage is to verify that it can talk to the scan chain
(list of TAPs) which has been configured.
It will warn if it doesn't find TAPs it expects to find,
or finds TAPs that aren't supposed to be there.
You should see no errors at this point.
If you see errors, resolve them by correcting the
commands you used to configure the server.
Common errors include using an initial JTAG speed that's too
fast, and not providing the right IDCODE values for the TAPs
on the scan chain.

Once OpenOCD has entered the run stage, a number of commands
become available.
A number of these relate to the debug targets you may have declared.
For example, the @command{mww} command will not be available until
a target has been successfully instantiated.
If you want to use those commands, you may need to force
entry to the run stage.

@deffn {Config Command} {init}
This command terminates the configuration stage and
enters the run stage. This helps when you need to have
the startup scripts manage tasks such as resetting the target,
programming flash, etc. To reset the CPU upon startup, add "init" and
"reset" at the end of the config script or at the end of the OpenOCD
command line using the @option{-c} command line switch.

If this command does not appear in any startup/configuration file
OpenOCD executes the command for you after processing all
configuration files and/or command line options.

@b{NOTE:} This command normally occurs near the end of your
openocd.cfg file to force OpenOCD to ``initialize'' and make the
targets ready. For example: If your openocd.cfg file needs to
read/write memory on your target, @command{init} must occur before
the memory read/write commands. This includes @command{nand probe}.

@command{init} calls the following internal OpenOCD commands to initialize
corresponding subsystems:
@deffn {Config Command} {target init}
@deffnx {Command} {transport init}
@deffnx {Command} {dap init}
@deffnx {Config Command} {flash init}
@deffnx {Config Command} {nand init}
@deffnx {Config Command} {pld init}
@deffnx {Command} {tpiu init}
@end deffn

At last, @command{init} executes all the commands that are specified in
the TCL list @var{post_init_commands}. The commands are executed in the
same order they occupy in the list. If one of the commands fails, then
the error is propagated and OpenOCD fails too.
@example
lappend post_init_commands @{echo "OpenOCD successfully initialized."@}
lappend post_init_commands @{echo "Have fun with OpenOCD !"@}
@end example
@end deffn

@deffn {Config Command} {noinit}
Prevent OpenOCD from implicit @command{init} call at the end of startup.
Allows issuing configuration commands over telnet or Tcl connection.
When you are done with configuration use @command{init} to enter
the run stage.
@end deffn

@deffn {Overridable Procedure} {jtag_init}
This is invoked at server startup to verify that it can talk
to the scan chain (list of TAPs) which has been configured.

The default implementation first tries @command{jtag arp_init},
which uses only a lightweight JTAG reset before examining the
scan chain.
If that fails, it tries again, using a harder reset
from the overridable procedure @command{init_reset}.

Implementations must have verified the JTAG scan chain before
they return.
This is done by calling @command{jtag arp_init}
(or @command{jtag arp_init-reset}).
@end deffn

@anchor{tcpipports}
@section TCP/IP Ports
@cindex TCP port
@cindex server
@cindex port
@cindex security
The OpenOCD server accepts remote commands in several syntaxes.
Each syntax uses a different TCP/IP port, which you may specify
only during configuration (before those ports are opened).

For reasons including security, you may wish to prevent remote
access using one or more of these ports.
In such cases, just specify the relevant port number as "disabled".
If you disable all access through TCP/IP, you will need to
use the command line @option{-pipe} option.

@anchor{gdb_port}
@deffn {Config Command} {gdb_port} [number]
@cindex GDB server
Normally gdb listens to a TCP/IP port, but GDB can also
communicate via pipes(stdin/out or named pipes). The name
"gdb_port" stuck because it covers probably more than 90% of
the normal use cases.

No arguments reports GDB port. "pipe" means listen to stdin
output to stdout, an integer is base port number, "disabled"
disables the gdb server.

When using "pipe", also use log_output to redirect the log
output to a file so as not to flood the stdin/out pipes.

Any other string is interpreted as named pipe to listen to.
Output pipe is the same name as input pipe, but with 'o' appended,
e.g. /var/gdb, /var/gdbo.

The GDB port for the first target will be the base port, the
second target will listen on gdb_port + 1, and so on.
When not specified during the configuration stage,
the port @var{number} defaults to 3333.
When @var{number} is not a numeric value, incrementing it to compute
the next port number does not work. In this case, specify the proper
@var{number} for each target by using the option @code{-gdb-port} of the
commands @command{target create} or @command{$target_name configure}.
@xref{gdbportoverride,,option -gdb-port}.

Note: when using "gdb_port pipe", increasing the default remote timeout in
gdb (with 'set remotetimeout') is recommended. An insufficient timeout may
cause initialization to fail with "Unknown remote qXfer reply: OK".
@end deffn

@deffn {Config Command} {tcl_port} [number]
Specify or query the port used for a simplified RPC
connection that can be used by clients to issue TCL commands and get the
output from the Tcl engine.
Intended as a machine interface.
When not specified during the configuration stage,
the port @var{number} defaults to 6666.
When specified as "disabled", this service is not activated.
@end deffn

@deffn {Config Command} {telnet_port} [number]
Specify or query the
port on which to listen for incoming telnet connections.
This port is intended for interaction with one human through TCL commands.
When not specified during the configuration stage,
the port @var{number} defaults to 4444.
When specified as "disabled", this service is not activated.
@end deffn

@anchor{gdbconfiguration}
@section GDB Configuration
@cindex GDB
@cindex GDB configuration
You can reconfigure some GDB behaviors if needed.
The ones listed here are static and global.
@xref{targetconfiguration,,Target Configuration}, about configuring individual targets.
@xref{targetevents,,Target Events}, about configuring target-specific event handling.

@anchor{gdbbreakpointoverride}
@deffn {Command} {gdb_breakpoint_override} [@option{hard}|@option{soft}|@option{disable}]
Force breakpoint type for gdb @command{break} commands.
This option supports GDB GUIs which don't
distinguish hard versus soft breakpoints, if the default OpenOCD and
GDB behaviour is not sufficient. GDB normally uses hardware
breakpoints if the memory map has been set up for flash regions.
@end deffn

@anchor{gdbflashprogram}
@deffn {Config Command} {gdb_flash_program} (@option{enable}|@option{disable})
Set to @option{enable} to cause OpenOCD to program the flash memory when a
vFlash packet is received.
The default behaviour is @option{enable}.
@end deffn

@deffn {Config Command} {gdb_memory_map} (@option{enable}|@option{disable})
Set to @option{enable} to cause OpenOCD to send the memory configuration to GDB when
requested. GDB will then know when to set hardware breakpoints, and program flash
using the GDB load command. @command{gdb_flash_program enable} must also be enabled
for flash programming to work.
Default behaviour is @option{enable}.
@xref{gdbflashprogram,,gdb_flash_program}.
@end deffn

@deffn {Config Command} {gdb_report_data_abort} (@option{enable}|@option{disable})
Specifies whether data aborts cause an error to be reported
by GDB memory read packets.
The default behaviour is @option{disable};
use @option{enable} see these errors reported.
@end deffn

@deffn {Config Command} {gdb_report_register_access_error} (@option{enable}|@option{disable})
Specifies whether register accesses requested by GDB register read/write
packets report errors or not.
The default behaviour is @option{disable};
use @option{enable} see these errors reported.
@end deffn

@deffn {Config Command} {gdb_target_description} (@option{enable}|@option{disable})
Set to @option{enable} to cause OpenOCD to send the target descriptions to gdb via qXfer:features:read packet.
The default behaviour is @option{enable}.
@end deffn

@deffn {Command} {gdb_save_tdesc}
Saves the target description file to the local file system.

The file name is @i{target_name}.xml.
@end deffn

@anchor{eventpolling}
@section Event Polling

Hardware debuggers are parts of asynchronous systems,
where significant events can happen at any time.
The OpenOCD server needs to detect some of these events,
so it can report them to through TCL command line
or to GDB.

Examples of such events include:

@itemize
@item One of the targets can stop running ... maybe it triggers
a code breakpoint or data watchpoint, or halts itself.
@item Messages may be sent over ``debug message'' channels ... many
targets support such messages sent over JTAG,
for receipt by the person debugging or tools.
@item Loss of power ... some adapters can detect these events.
@item Resets not issued through JTAG ... such reset sources
can include button presses or other system hardware, sometimes
including the target itself (perhaps through a watchdog).
@item Debug instrumentation sometimes supports event triggering
such as ``trace buffer full'' (so it can quickly be emptied)
or other signals (to correlate with code behavior).
@end itemize

None of those events are signaled through standard JTAG signals.
However, most conventions for JTAG connectors include voltage
level and system reset (SRST) signal detection.
Some connectors also include instrumentation signals, which
can imply events when those signals are inputs.

In general, OpenOCD needs to periodically check for those events,
either by looking at the status of signals on the JTAG connector
or by sending synchronous ``tell me your status'' JTAG requests
to the various active targets.
There is a command to manage and monitor that polling,
which is normally done in the background.

@deffn {Command} {poll} [@option{on}|@option{off}]
Poll the current target for its current state.
(Also, @pxref{targetcurstate,,target curstate}.)
If that target is in debug mode, architecture
specific information about the current state is printed.
An optional parameter
allows background polling to be enabled and disabled.

You could use this from the TCL command shell, or
from GDB using @command{monitor poll} command.
Leave background polling enabled while you're using GDB.
@example
> poll
background polling: on
target state: halted
target halted in ARM state due to debug-request, \
               current mode: Supervisor
cpsr: 0x800000d3 pc: 0x11081bfc
MMU: disabled, D-Cache: disabled, I-Cache: enabled
>
@end example
@end deffn

@node Debug Adapter Configuration
@chapter Debug Adapter Configuration
@cindex config file, interface
@cindex interface config file

Correctly installing OpenOCD includes making your operating system give
OpenOCD access to debug adapters. Once that has been done, Tcl commands
are used to select which one is used, and to configure how it is used.

@quotation Note
Because OpenOCD started out with a focus purely on JTAG, you may find
places where it wrongly presumes JTAG is the only transport protocol
in use. Be aware that recent versions of OpenOCD are removing that
limitation. JTAG remains more functional than most other transports.
Other transports do not support boundary scan operations, or may be
specific to a given chip vendor. Some might be usable only for
programming flash memory, instead of also for debugging.
@end quotation

Debug Adapters/Interfaces/Dongles are normally configured
through commands in an interface configuration
file which is sourced by your @file{openocd.cfg} file, or
through a command line @option{-f interface/....cfg} option.

@example
source [find interface/olimex-jtag-tiny.cfg]
@end example

These commands tell
OpenOCD what type of JTAG adapter you have, and how to talk to it.
A few cases are so simple that you only need to say what driver to use:

@example
# jlink interface
adapter driver jlink
@end example

Most adapters need a bit more configuration than that.


@section Adapter Configuration

The @command{adapter driver} command tells OpenOCD what type of debug adapter you are
using. Depending on the type of adapter, you may need to use one or
more additional commands to further identify or configure the adapter.

@deffn {Config Command} {adapter driver} name
Use the adapter driver @var{name} to connect to the
target.
@end deffn

@deffn {Command} {adapter list}
List the debug adapter drivers that have been built into
the running copy of OpenOCD.
@end deffn
@deffn {Config Command} {adapter transports} transport_name+
Specifies the transports supported by this debug adapter.
The adapter driver builds-in similar knowledge; use this only
when external configuration (such as jumpering) changes what
the hardware can support.
@end deffn



@deffn {Command} {adapter name}
Returns the name of the debug adapter driver being used.
@end deffn

@anchor{adapter_usb_location}
@deffn {Config Command} {adapter usb location} [<bus>-<port>[.<port>]...]
Displays or specifies the physical USB port of the adapter to use. The path
roots at @var{bus} and walks down the physical ports, with each
@var{port} option specifying a deeper level in the bus topology, the last
@var{port} denoting where the target adapter is actually plugged.
The USB bus topology can be queried with the command @emph{lsusb -t} or @emph{dmesg}.

This command is only available if your libusb1 is at least version 1.0.16.
@end deffn

@deffn {Config Command} {adapter serial} serial_string
Specifies the @var{serial_string} of the adapter to use.
If this command is not specified, serial strings are not checked.
Only the following adapter drivers use the serial string from this command:
aice (aice_usb), arm-jtag-ew, cmsis_dap, ft232r, ftdi, hla (stlink, ti-icdi), jlink, kitprog, opendus,
openjtag, osbdm, presto, rlink, st-link, usb_blaster (ublast2), usbprog, vsllink, xds110.
@end deffn

@section Interface Drivers

Each of the interface drivers listed here must be explicitly
enabled when OpenOCD is configured, in order to be made
available at run time.

@deffn {Interface Driver} {amt_jtagaccel}
Amontec Chameleon in its JTAG Accelerator configuration,
connected to a PC's EPP mode parallel port.
This defines some driver-specific commands:

@deffn {Config Command} {parport port} number
Specifies either the address of the I/O port (default: 0x378 for LPT1) or
the number of the @file{/dev/parport} device.
@end deffn

@deffn {Config Command} {rtck} [@option{enable}|@option{disable}]
Displays status of RTCK option.
Optionally sets that option first.
@end deffn
@end deffn

@deffn {Interface Driver} {arm-jtag-ew}
Olimex ARM-JTAG-EW USB adapter
This has one driver-specific command:

@deffn {Command} {armjtagew_info}
Logs some status
@end deffn
@end deffn

@deffn {Interface Driver} {at91rm9200}
Supports bitbanged JTAG from the local system,
presuming that system is an Atmel AT91rm9200
and a specific set of GPIOs is used.
@c command:     at91rm9200_device NAME
@c chooses among list of bit configs ... only one option
@end deffn

@deffn {Interface Driver} {cmsis-dap}
ARM CMSIS-DAP compliant based adapter v1 (USB HID based)
or v2 (USB bulk).

@deffn {Config Command} {cmsis_dap_vid_pid} [vid pid]+
The vendor ID and product ID of the CMSIS-DAP device. If not specified
the driver will attempt to auto detect the CMSIS-DAP device.
Currently, up to eight [@var{vid}, @var{pid}] pairs may be given, e.g.
@example
cmsis_dap_vid_pid 0xc251 0xf001 0x0d28 0x0204
@end example
@end deffn

@deffn {Config Command} {cmsis_dap_backend} [@option{auto}|@option{usb_bulk}|@option{hid}]
Specifies how to communicate with the adapter:

@itemize @minus
@item @option{hid} Use HID generic reports - CMSIS-DAP v1
@item @option{usb_bulk} Use USB bulk - CMSIS-DAP v2
@item @option{auto} First try USB bulk CMSIS-DAP v2, if not found try HID CMSIS-DAP v1.
This is the default if @command{cmsis_dap_backend} is not specified.
@end itemize
@end deffn

@deffn {Config Command} {cmsis_dap_usb interface} [number]
Specifies the @var{number} of the USB interface to use in v2 mode (USB bulk).
In most cases need not to be specified and interfaces are searched by
interface string or for user class interface.
@end deffn

@deffn {Command} {cmsis-dap info}
Display various device information, like hardware version, firmware version, current bus status.
@end deffn

@deffn {Command} {cmsis-dap cmd} number number ...
Execute an arbitrary CMSIS-DAP command. Use for adapter testing or for handling
of an adapter vendor specific command from a Tcl script.

Take given numbers as bytes, assemble a CMSIS-DAP protocol command packet
from them and send it to the adapter. The first 4 bytes of the adapter response
are logged.
See @url{https://arm-software.github.io/CMSIS_5/DAP/html/group__DAP__Commands__gr.html}
@end deffn
@end deffn

@deffn {Interface Driver} {dummy}
A dummy software-only driver for debugging.
@end deffn

@deffn {Interface Driver} {ep93xx}
Cirrus Logic EP93xx based single-board computer bit-banging (in development)
@end deffn

@deffn {Interface Driver} {ftdi}
This driver is for adapters using the MPSSE (Multi-Protocol Synchronous Serial
Engine) mode built into many FTDI chips, such as the FT2232, FT4232 and FT232H.

The driver is using libusb-1.0 in asynchronous mode to talk to the FTDI device,
bypassing intermediate libraries like libftdi.

Support for new FTDI based adapters can be added completely through
configuration files, without the need to patch and rebuild OpenOCD.

The driver uses a signal abstraction to enable Tcl configuration files to
define outputs for one or several FTDI GPIO. These outputs can then be
controlled using the @command{ftdi set_signal} command. Special signal names
are reserved for nTRST, nSRST and LED (for blink) so that they, if defined,
will be used for their customary purpose. Inputs can be read using the
@command{ftdi get_signal} command.

To support SWD, a signal named SWD_EN must be defined. It is set to 1 when the
SWD protocol is selected. When set, the adapter should route the SWDIO pin to
the data input. An SWDIO_OE signal, if defined, will be set to 1 or 0 as
required by the protocol, to tell the adapter to drive the data output onto
the SWDIO pin or keep the SWDIO pin Hi-Z, respectively.

Depending on the type of buffer attached to the FTDI GPIO, the outputs have to
be controlled differently. In order to support tristateable signals such as
nSRST, both a data GPIO and an output-enable GPIO can be specified for each
signal. The following output buffer configurations are supported:

@itemize @minus
@item Push-pull with one FTDI output as (non-)inverted data line
@item Open drain with one FTDI output as (non-)inverted output-enable
@item Tristate with one FTDI output as (non-)inverted data line and another
      FTDI output as (non-)inverted output-enable
@item Unbuffered, using the FTDI GPIO as a tristate output directly by
      switching data and direction as necessary
@end itemize

These interfaces have several commands, used to configure the driver
before initializing the JTAG scan chain:

@deffn {Config Command} {ftdi vid_pid} [vid pid]+
The vendor ID and product ID of the adapter. Up to eight
[@var{vid}, @var{pid}] pairs may be given, e.g.
@example
ftdi vid_pid 0x0403 0xcff8 0x15ba 0x0003
@end example
@end deffn

@deffn {Config Command} {ftdi device_desc} description
Provides the USB device description (the @emph{iProduct string})
of the adapter. If not specified, the device description is ignored
during device selection.
@end deffn

@deffn {Config Command} {ftdi channel} channel
Selects the channel of the FTDI device to use for MPSSE operations. Most
adapters use the default, channel 0, but there are exceptions.
@end deffn

@deffn {Config Command} {ftdi layout_init} data direction
Specifies the initial values of the FTDI GPIO data and direction registers.
Each value is a 16-bit number corresponding to the concatenation of the high
and low FTDI GPIO registers. The values should be selected based on the
schematics of the adapter, such that all signals are set to safe levels with
minimal impact on the target system. Avoid floating inputs, conflicting outputs
and initially asserted reset signals.
@end deffn

@deffn {Command} {ftdi layout_signal} name [@option{-data}|@option{-ndata} data_mask] [@option{-input}|@option{-ninput} input_mask] [@option{-oe}|@option{-noe} oe_mask] [@option{-alias}|@option{-nalias} name]
Creates a signal with the specified @var{name}, controlled by one or more FTDI
GPIO pins via a range of possible buffer connections. The masks are FTDI GPIO
register bitmasks to tell the driver the connection and type of the output
buffer driving the respective signal. @var{data_mask} is the bitmask for the
pin(s) connected to the data input of the output buffer. @option{-ndata} is
used with inverting data inputs and @option{-data} with non-inverting inputs.
The @option{-oe} (or @option{-noe}) option tells where the output-enable (or
not-output-enable) input to the output buffer is connected. The options
@option{-input} and @option{-ninput} specify the bitmask for pins to be read
with the method @command{ftdi get_signal}.

Both @var{data_mask} and @var{oe_mask} need not be specified. For example, a
simple open-collector transistor driver would be specified with @option{-oe}
only. In that case the signal can only be set to drive low or to Hi-Z and the
driver will complain if the signal is set to drive high. Which means that if
it's a reset signal, @command{reset_config} must be specified as
@option{srst_open_drain}, not @option{srst_push_pull}.

A special case is provided when @option{-data} and @option{-oe} is set to the
same bitmask. Then the FTDI pin is considered being connected straight to the
target without any buffer. The FTDI pin is then switched between output and
input as necessary to provide the full set of low, high and Hi-Z
characteristics. In all other cases, the pins specified in a signal definition
are always driven by the FTDI.

If @option{-alias} or @option{-nalias} is used, the signal is created
identical (or with data inverted) to an already specified signal
@var{name}.
@end deffn

@deffn {Command} {ftdi set_signal} name @option{0}|@option{1}|@option{z}
Set a previously defined signal to the specified level.
@itemize @minus
@item @option{0}, drive low
@item @option{1}, drive high
@item @option{z}, set to high-impedance
@end itemize
@end deffn

@deffn {Command} {ftdi get_signal} name
Get the value of a previously defined signal.
@end deffn

@deffn {Command} {ftdi tdo_sample_edge} @option{rising}|@option{falling}
Configure TCK edge at which the adapter samples the value of the TDO signal

Due to signal propagation delays, sampling TDO on rising TCK can become quite
peculiar at high JTAG clock speeds. However, FTDI chips offer a possibility to sample
TDO on falling edge of TCK. With some board/adapter configurations, this may increase
stability at higher JTAG clocks.
@itemize @minus
@item @option{rising}, sample TDO on rising edge of TCK - this is the default
@item @option{falling}, sample TDO on falling edge of TCK
@end itemize
@end deffn

For example adapter definitions, see the configuration files shipped in the
@file{interface/ftdi} directory.

@end deffn

@deffn {Interface Driver} {ft232r}
This driver is implementing synchronous bitbang mode of an FTDI FT232R,
FT230X, FT231X and similar USB UART bridge ICs by reusing RS232 signals as GPIO.
It currently doesn't support using CBUS pins as GPIO.

List of connections (default physical pin numbers for FT232R in 28-pin SSOP package):
@itemize @minus
@item RXD(5) - TDI
@item TXD(1) - TCK
@item RTS(3) - TDO
@item CTS(11) - TMS
@item DTR(2) - TRST
@item DCD(10) - SRST
@end itemize

User can change default pinout by supplying configuration
commands with GPIO numbers or RS232 signal names.
GPIO numbers correspond to bit numbers in FTDI GPIO register.
They differ from physical pin numbers.
For details see actual FTDI chip datasheets.
Every JTAG line must be configured to unique GPIO number
different than any other JTAG line, even those lines
that are sometimes not used like TRST or SRST.

FT232R
@itemize @minus
@item bit 7 - RI
@item bit 6 - DCD
@item bit 5 - DSR
@item bit 4 - DTR
@item bit 3 - CTS
@item bit 2 - RTS
@item bit 1 - RXD
@item bit 0 - TXD
@end itemize

These interfaces have several commands, used to configure the driver
before initializing the JTAG scan chain:

@deffn {Config Command} {ft232r vid_pid} @var{vid} @var{pid}
The vendor ID and product ID of the adapter. If not specified, default
0x0403:0x6001 is used.
@end deffn

@deffn {Config Command} {ft232r jtag_nums} @var{tck} @var{tms} @var{tdi} @var{tdo}
Set four JTAG GPIO numbers at once.
If not specified, default 0 3 1 2 or TXD CTS RXD RTS is used.
@end deffn

@deffn {Config Command} {ft232r tck_num} @var{tck}
Set TCK GPIO number. If not specified, default 0 or TXD is used.
@end deffn

@deffn {Config Command} {ft232r tms_num} @var{tms}
Set TMS GPIO number. If not specified, default 3 or CTS is used.
@end deffn

@deffn {Config Command} {ft232r tdi_num} @var{tdi}
Set TDI GPIO number. If not specified, default 1 or RXD is used.
@end deffn

@deffn {Config Command} {ft232r tdo_num} @var{tdo}
Set TDO GPIO number. If not specified, default 2 or RTS is used.
@end deffn

@deffn {Config Command} {ft232r trst_num} @var{trst}
Set TRST GPIO number. If not specified, default 4 or DTR is used.
@end deffn

@deffn {Config Command} {ft232r srst_num} @var{srst}
Set SRST GPIO number. If not specified, default 6 or DCD is used.
@end deffn

@deffn {Config Command} {ft232r restore_serial} @var{word}
Restore serial port after JTAG. This USB bitmode control word
(16-bit) will be sent before quit. Lower byte should
set GPIO direction register to a "sane" state:
0x15 for TXD RTS DTR as outputs (1), others as inputs (0). Higher
byte is usually 0 to disable bitbang mode.
When kernel driver reattaches, serial port should continue to work.
Value 0xFFFF disables sending control word and serial port,
then kernel driver will not reattach.
If not specified, default 0xFFFF is used.
@end deffn

@end deffn

@deffn {Interface Driver} {remote_bitbang}
Drive JTAG from a remote process. This sets up a UNIX or TCP socket connection
with a remote process and sends ASCII encoded bitbang requests to that process
instead of directly driving JTAG.

The remote_bitbang driver is useful for debugging software running on
processors which are being simulated.

@deffn {Config Command} {remote_bitbang port} number
Specifies the TCP port of the remote process to connect to or 0 to use UNIX
sockets instead of TCP.
@end deffn

@deffn {Config Command} {remote_bitbang host} hostname
Specifies the hostname of the remote process to connect to using TCP, or the
name of the UNIX socket to use if remote_bitbang port is 0.
@end deffn

For example, to connect remotely via TCP to the host foobar you might have
something like:

@example
adapter driver remote_bitbang
remote_bitbang port 3335
remote_bitbang host foobar
@end example

To connect to another process running locally via UNIX sockets with socket
named mysocket:

@example
adapter driver remote_bitbang
remote_bitbang port 0
remote_bitbang host mysocket
@end example
@end deffn

@deffn {Interface Driver} {usb_blaster}
USB JTAG/USB-Blaster compatibles over one of the userspace libraries
for FTDI chips. These interfaces have several commands, used to
configure the driver before initializing the JTAG scan chain:

@deffn {Config Command} {usb_blaster vid_pid} vid pid
The vendor ID and product ID of the FTDI FT245 device. If not specified,
default values are used.
Currently, only one @var{vid}, @var{pid} pair may be given, e.g. for
Altera USB-Blaster (default):
@example
usb_blaster vid_pid 0x09FB 0x6001
@end example
The following VID/PID is for Kolja Waschk's USB JTAG:
@example
usb_blaster vid_pid 0x16C0 0x06AD
@end example
@end deffn

@deffn {Command} {usb_blaster pin} (@option{pin6}|@option{pin8}) (@option{0}|@option{1}|@option{s}|@option{t})
Sets the state or function of the unused GPIO pins on USB-Blasters
(pins 6 and 8 on the female JTAG header). These pins can be used as
SRST and/or TRST provided the appropriate connections are made on the
target board.

For example, to use pin 6 as SRST:
@example
usb_blaster pin pin6 s
reset_config srst_only
@end example
@end deffn

@deffn {Config Command} {usb_blaster lowlevel_driver} (@option{ftdi}|@option{ublast2})
Chooses the low level access method for the adapter. If not specified,
@option{ftdi} is selected unless it wasn't enabled during the
configure stage. USB-Blaster II needs @option{ublast2}.
@end deffn

@deffn {Config Command} {usb_blaster firmware} @var{path}
This command specifies @var{path} to access USB-Blaster II firmware
image. To be used with USB-Blaster II only.
@end deffn

@end deffn

@deffn {Interface Driver} {gw16012}
Gateworks GW16012 JTAG programmer.
This has one driver-specific command:

@deffn {Config Command} {parport port} [port_number]
Display either the address of the I/O port
(default: 0x378 for LPT1) or the number of the @file{/dev/parport} device.
If a parameter is provided, first switch to use that port.
This is a write-once setting.
@end deffn
@end deffn

@deffn {Interface Driver} {jlink}
SEGGER J-Link family of USB adapters. It currently supports JTAG and SWD
transports.

@quotation Compatibility Note
SEGGER released many firmware versions for the many hardware versions they
produced. OpenOCD was extensively tested and intended to run on all of them,
but some combinations were reported as incompatible. As a general
recommendation, it is advisable to use the latest firmware version
available for each hardware version. However the current V8 is a moving
target, and SEGGER firmware versions released after the OpenOCD was
released may not be compatible. In such cases it is recommended to
revert to the last known functional version. For 0.5.0, this is from
"Feb  8 2012 14:30:39", packed with 4.42c. For 0.6.0, the last known
version is from "May  3 2012 18:36:22", packed with 4.46f.
@end quotation

@deffn {Command} {jlink hwstatus}
Display various hardware related information, for example target voltage and pin
states.
@end deffn
@deffn {Command} {jlink freemem}
Display free device internal memory.
@end deffn
@deffn {Command} {jlink jtag} [@option{2}|@option{3}]
Set the JTAG command version to be used. Without argument, show the actual JTAG
command version.
@end deffn
@deffn {Command} {jlink config}
Display the device configuration.
@end deffn
@deffn {Command} {jlink config targetpower} [@option{on}|@option{off}]
Set the target power state on JTAG-pin 19. Without argument, show the target
power state.
@end deffn
@deffn {Command} {jlink config mac} [@option{ff:ff:ff:ff:ff:ff}]
Set the MAC address of the device. Without argument, show the MAC address.
@end deffn
@deffn {Command} {jlink config ip} [@option{A.B.C.D}(@option{/E}|@option{F.G.H.I})]
Set the IP configuration of the device, where A.B.C.D is the IP address, E the
bit of the subnet mask and F.G.H.I the subnet mask. Without arguments, show the
IP configuration.
@end deffn
@deffn {Command} {jlink config usb} [@option{0} to @option{3}]
Set the USB address of the device. This will also change the USB Product ID
(PID) of the device. Without argument, show the USB address.
@end deffn
@deffn {Command} {jlink config reset}
Reset the current configuration.
@end deffn
@deffn {Command} {jlink config write}
Write the current configuration to the internal persistent storage.
@end deffn
@deffn {Command} {jlink emucom write} <channel> <data>
Write data to an EMUCOM channel. The data needs to be encoded as hexadecimal
pairs.

The following example shows how to write the three bytes 0xaa, 0x0b and 0x23 to
the EMUCOM channel 0x10:
@example
> jlink emucom write 0x10 aa0b23
@end example
@end deffn
@deffn {Command} {jlink emucom read} <channel> <length>
Read data from an EMUCOM channel. The read data is encoded as hexadecimal
pairs.

The following example shows how to read 4 bytes from the EMUCOM channel 0x0:
@example
> jlink emucom read 0x0 4
77a90000
@end example
@end deffn
@deffn {Config Command} {jlink usb} <@option{0} to @option{3}>
Set the USB address of the interface, in case more than one adapter is connected
to the host. If not specified, USB addresses are not considered. Device
selection via USB address is not always unambiguous. It is recommended to use
the serial number instead, if possible.

As a configuration command, it can be used only before 'init'.
@end deffn
@end deffn

@deffn {Interface Driver} {kitprog}
This driver is for Cypress Semiconductor's KitProg adapters. The KitProg is an
SWD-only adapter that is designed to be used with Cypress's PSoC and PRoC device
families, but it is possible to use it with some other devices. If you are using
this adapter with a PSoC or a PRoC, you may need to add
@command{kitprog_init_acquire_psoc} or @command{kitprog acquire_psoc} to your
configuration script.

Note that this driver is for the proprietary KitProg protocol, not the CMSIS-DAP
mode introduced in firmware 2.14. If the KitProg is in CMSIS-DAP mode, it cannot
be used with this driver, and must either be used with the cmsis-dap driver or
switched back to KitProg mode. See the Cypress KitProg User Guide for
instructions on how to switch KitProg modes.

Known limitations:
@itemize @bullet
@item The frequency of SWCLK cannot be configured, and varies between 1.6 MHz
and 2.7 MHz.
@item For firmware versions below 2.14, "JTAG to SWD" sequences are replaced by
"SWD line reset" in the driver. This is for two reasons. First, the KitProg does
not support sending arbitrary SWD sequences, and only firmware 2.14 and later
implement both "JTAG to SWD" and "SWD line reset" in firmware. Earlier firmware
versions only implement "SWD line reset". Second, due to a firmware quirk, an
SWD sequence must be sent after every target reset in order to re-establish
communications with the target.
@item Due in part to the limitation above, KitProg devices with firmware below
version 2.14 will need to use @command{kitprog_init_acquire_psoc} in order to
communicate with PSoC 5LP devices. This is because, assuming debug is not
disabled on the PSoC, the PSoC 5LP needs its JTAG interface switched to SWD
mode before communication can begin, but prior to firmware 2.14, "JTAG to SWD"
could only be sent with an acquisition sequence.
@end itemize

@deffn {Config Command} {kitprog_init_acquire_psoc}
Indicate that a PSoC acquisition sequence needs to be run during adapter init.
Please be aware that the acquisition sequence hard-resets the target.
@end deffn

@deffn {Command} {kitprog acquire_psoc}
Run a PSoC acquisition sequence immediately. Typically, this should not be used
outside of the target-specific configuration scripts since it hard-resets the
target as a side-effect.
This is necessary for "reset halt" on some PSoC 4 series devices.
@end deffn

@deffn {Command} {kitprog info}
Display various adapter information, such as the hardware version, firmware
version, and target voltage.
@end deffn
@end deffn

@deffn {Interface Driver} {parport}
Supports PC parallel port bit-banging cables:
Wigglers, PLD download cable, and more.
These interfaces have several commands, used to configure the driver
before initializing the JTAG scan chain:

@deffn {Config Command} {parport cable} name
Set the layout of the parallel port cable used to connect to the target.
This is a write-once setting.
Currently valid cable @var{name} values include:

@itemize @minus
@item @b{altium} Altium Universal JTAG cable.
@item @b{arm-jtag} Same as original wiggler except SRST and
TRST connections reversed and TRST is also inverted.
@item @b{chameleon} The Amontec Chameleon's CPLD when operated
in configuration mode. This is only used to
program the Chameleon itself, not a connected target.
@item @b{dlc5} The Xilinx Parallel cable III.
@item @b{flashlink} The ST Parallel cable.
@item @b{lattice} Lattice ispDOWNLOAD Cable
@item @b{old_amt_wiggler} The Wiggler configuration that comes with
some versions of
Amontec's Chameleon Programmer. The new version available from
the website uses the original Wiggler layout ('@var{wiggler}')
@item @b{triton} The parallel port adapter found on the
``Karo Triton 1 Development Board''.
This is also the layout used by the HollyGates design
(see @uref{http://www.lartmaker.nl/projects/jtag/}).
@item @b{wiggler} The original Wiggler layout, also supported by
several clones, such as the Olimex ARM-JTAG
@item @b{wiggler2} Same as original wiggler except an led is fitted on D5.
@item @b{wiggler_ntrst_inverted} Same as original wiggler except TRST is inverted.
@end itemize
@end deffn

@deffn {Config Command} {parport port} [port_number]
Display either the address of the I/O port
(default: 0x378 for LPT1) or the number of the @file{/dev/parport} device.
If a parameter is provided, first switch to use that port.
This is a write-once setting.

When using PPDEV to access the parallel port, use the number of the parallel port:
@option{parport port 0} (the default). If @option{parport port 0x378} is specified
you may encounter a problem.
@end deffn

@deffn {Config Command} {parport toggling_time} [nanoseconds]
Displays how many nanoseconds the hardware needs to toggle TCK;
the parport driver uses this value to obey the
@command{adapter speed} configuration.
When the optional @var{nanoseconds} parameter is given,
that setting is changed before displaying the current value.

The default setting should work reasonably well on commodity PC hardware.
However, you may want to calibrate for your specific hardware.
@quotation Tip
To measure the toggling time with a logic analyzer or a digital storage
oscilloscope, follow the procedure below:
@example
> parport toggling_time 1000
> adapter speed 500
@end example
This sets the maximum JTAG clock speed of the hardware, but
the actual speed probably deviates from the requested 500 kHz.
Now, measure the time between the two closest spaced TCK transitions.
You can use @command{runtest 1000} or something similar to generate a
large set of samples.
Update the setting to match your measurement:
@example
> parport toggling_time <measured nanoseconds>
@end example
Now the clock speed will be a better match for @command{adapter speed}
command given in OpenOCD scripts and event handlers.

You can do something similar with many digital multimeters, but note
that you'll probably need to run the clock continuously for several
seconds before it decides what clock rate to show. Adjust the
toggling time up or down until the measured clock rate is a good
match with the rate you specified in the @command{adapter speed} command;
be conservative.
@end quotation
@end deffn

@deffn {Config Command} {parport write_on_exit} (@option{on}|@option{off})
This will configure the parallel driver to write a known
cable-specific value to the parallel interface on exiting OpenOCD.
@end deffn

For example, the interface configuration file for a
classic ``Wiggler'' cable on LPT2 might look something like this:

@example
adapter driver parport
parport port 0x278
parport cable wiggler
@end example
@end deffn

@deffn {Interface Driver} {presto}
ASIX PRESTO USB JTAG programmer.
@end deffn

@deffn {Interface Driver} {rlink}
Raisonance RLink USB adapter
@end deffn

@deffn {Interface Driver} {usbprog}
usbprog is a freely programmable USB adapter.
@end deffn

@deffn {Interface Driver} {vsllink}
vsllink is part of Versaloon which is a versatile USB programmer.

@quotation Note
This defines quite a few driver-specific commands,
which are not currently documented here.
@end quotation
@end deffn

@anchor{hla_interface}
@deffn {Interface Driver} {hla}
This is a driver that supports multiple High Level Adapters.
This type of adapter does not expose some of the lower level api's
that OpenOCD would normally use to access the target.

Currently supported adapters include the STMicroelectronics ST-LINK, TI ICDI
and Nuvoton Nu-Link.
ST-LINK firmware version >= V2.J21.S4 recommended due to issues with earlier
versions of firmware where serial number is reset after first use.  Suggest
using ST firmware update utility to upgrade ST-LINK firmware even if current
version reported is V2.J21.S4.

@deffn {Config Command} {hla_device_desc} description
Currently Not Supported.
@end deffn

@deffn {Config Command} {hla_layout} (@option{stlink}|@option{icdi}|@option{nulink})
Specifies the adapter layout to use.
@end deffn

@deffn {Config Command} {hla_vid_pid} [vid pid]+
Pairs of vendor IDs and product IDs of the device.
@end deffn

@deffn {Config Command} {hla_stlink_backend} (usb | tcp [port])
@emph{ST-Link only:} Choose between 'exclusive' USB communication (the default backend) or
'shared' mode using ST-Link TCP server (the default port is 7184).

@emph{Note:} ST-Link TCP server is a binary application provided by ST
available from @url{https://www.st.com/en/development-tools/st-link-server.html,
ST-LINK server software module}.
@end deffn

@deffn {Command} {hla_command} command
Execute a custom adapter-specific command. The @var{command} string is
passed as is to the underlying adapter layout handler.
@end deffn
@end deffn

@anchor{st_link_dap_interface}
@deffn {Interface Driver} {st-link}
This is a driver that supports STMicroelectronics adapters ST-LINK/V2
(from firmware V2J24) and STLINK-V3, thanks to a new API that provides
directly access the arm ADIv5 DAP.

The new API provide access to multiple AP on the same DAP, but the
maximum number of the AP port is limited by the specific firmware version
(e.g. firmware V2J29 has 3 as maximum AP number, while V2J32 has 8).
An error is returned for any AP number above the maximum allowed value.

@emph{Note:} Either these same adapters and their older versions are
also supported by @ref{hla_interface, the hla interface driver}.

@deffn {Config Command} {st-link backend} (usb | tcp [port])
Choose between 'exclusive' USB communication (the default backend) or
'shared' mode using ST-Link TCP server (the default port is 7184).

@emph{Note:} ST-Link TCP server is a binary application provided by ST
available from @url{https://www.st.com/en/development-tools/st-link-server.html,
ST-LINK server software module}.

@emph{Note:} ST-Link TCP server does not support the SWIM transport.
@end deffn

@deffn {Config Command} {st-link vid_pid} [vid pid]+
Pairs of vendor IDs and product IDs of the device.
@end deffn

@deffn {Command} {st-link cmd} rx_n (tx_byte)+
Sends an arbitrary command composed by the sequence of bytes @var{tx_byte}
and receives @var{rx_n} bytes.

For example, the command to read the target's supply voltage is one byte 0xf7 followed
by 15 bytes zero. It returns 8 bytes, where the first 4 bytes represent the ADC sampling
of the reference voltage 1.2V and the last 4 bytes represent the ADC sampling of half
the target's supply voltage.
@example
> st-link cmd 8 0xf7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0xf1 0x05 0x00 0x00 0x0b 0x08 0x00 0x00
@end example
The result can be converted to Volts (ignoring the most significant bytes, always zero)
@example
> set a [st-link cmd 8 0xf7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
> set n [expr @{[lindex $a 4] + 256 * [lindex $a 5]@}]
> set d [expr @{[lindex $a 0] + 256 * [lindex $a 1]@}]
> echo [expr @{2 * 1.2 * $n / $d@}]
3.24891518738
@end example
@end deffn
@end deffn

@deffn {Interface Driver} {opendous}
opendous-jtag is a freely programmable USB adapter.
@end deffn

@deffn {Interface Driver} {ulink}
This is the Keil ULINK v1 JTAG debugger.
@end deffn

@deffn {Interface Driver} {xds110}
The XDS110 is included as the embedded debug probe on many Texas Instruments
LaunchPad evaluation boards. The XDS110 is also available as a stand-alone USB
debug probe with the added capability to supply power to the target board. The
following commands are supported by the XDS110 driver:

@deffn {Config Command} {xds110 supply} voltage_in_millivolts
Available only on the XDS110 stand-alone probe. Sets the voltage level of the
XDS110 power supply. A value of 0 leaves the supply off. Otherwise, the supply
can be set to any value in the range 1800 to 3600 millivolts.
@end deffn

@deffn {Command} {xds110 info}
Displays information about the connected XDS110 debug probe (e.g. firmware
version).
@end deffn
@end deffn

@deffn {Interface Driver} {xlnx_pcie_xvc}
This driver supports the Xilinx Virtual Cable (XVC) over PCI Express.
It is commonly found in Xilinx based PCI Express designs. It allows debugging
fabric based JTAG/SWD devices such as Cortex-M1/M3 microcontrollers. Access to this is
exposed via extended capability registers in the PCI Express configuration space.

For more information see Xilinx PG245 (Section on From_PCIE_to_JTAG mode).

@deffn {Config Command} {xlnx_pcie_xvc config} device
Specifies the PCI Express device via parameter @var{device} to use.

The correct value for @var{device} can be obtained by looking at the output
of lscpi -D (first column) for the corresponding device.

The string will be of the format "DDDD:BB:SS.F" such as "0000:65:00.1".

@end deffn
@end deffn

@deffn {Interface Driver} {bcm2835gpio}
This SoC is present in Raspberry Pi which is a cheap single-board computer
exposing some GPIOs on its expansion header.

The driver accesses memory-mapped GPIO peripheral registers directly
for maximum performance, but the only possible race condition is for
the pins' modes/muxing (which is highly unlikely), so it should be
able to coexist nicely with both sysfs bitbanging and various
peripherals' kernel drivers. The driver restores the previous
configuration on exit.

GPIO numbers >= 32 can't be used for performance reasons.

See @file{interface/raspberrypi-native.cfg} for a sample config and
pinout.

@deffn {Config Command} {bcm2835gpio jtag_nums} @var{tck} @var{tms} @var{tdi} @var{tdo}
Set JTAG transport GPIO numbers for TCK, TMS, TDI, and TDO (in that order).
Must be specified to enable JTAG transport. These pins can also be specified
individually.
@end deffn

@deffn {Config Command} {bcm2835gpio tck_num} @var{tck}
Set TCK GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{bcm2835gpio jtag_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio tms_num} @var{tms}
Set TMS GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{bcm2835gpio jtag_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio tdo_num} @var{tdo}
Set TDO GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{bcm2835gpio jtag_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio tdi_num} @var{tdi}
Set TDI GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{bcm2835gpio jtag_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio swd_nums} @var{swclk} @var{swdio}
Set SWD transport GPIO numbers for SWCLK and SWDIO (in that order). Must be
specified to enable SWD transport. These pins can also be specified individually.
@end deffn

@deffn {Config Command} {bcm2835gpio swclk_num} @var{swclk}
Set SWCLK GPIO number. Must be specified to enable SWD transport. Can also be
specified using the configuration command @command{bcm2835gpio swd_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio swdio_num} @var{swdio}
Set SWDIO GPIO number. Must be specified to enable SWD transport. Can also be
specified using the configuration command @command{bcm2835gpio swd_nums}.
@end deffn

@deffn {Config Command} {bcm2835gpio swdio_dir_num} @var{swdio} @var{dir}
Set SWDIO direction control pin GPIO number. If specified, this pin can be used
to control the direction of an external buffer on the SWDIO pin (set=output
mode, clear=input mode). If not specified, this feature is disabled.
@end deffn

@deffn {Config Command} {bcm2835gpio srst_num} @var{srst}
Set SRST GPIO number. Must be specified to enable SRST.
@end deffn

@deffn {Config Command} {bcm2835gpio trst_num} @var{trst}
Set TRST GPIO number. Must be specified to enable TRST.
@end deffn

@deffn {Config Command} {bcm2835gpio speed_coeffs} @var{speed_coeff} @var{speed_offset}
Set SPEED_COEFF and SPEED_OFFSET for delay calculations. If unspecified,
speed_coeff defaults to 113714, and speed_offset defaults to 28.
@end deffn

@deffn {Config Command} {bcm2835gpio peripheral_base} @var{base}
Set the peripheral base register address to access GPIOs. For the RPi1, use
0x20000000. For RPi2 and RPi3, use 0x3F000000. For RPi4, use 0xFE000000. A full
list can be found in the
@uref{https://www.raspberrypi.org/documentation/hardware/raspberrypi/peripheral_addresses.md, official guide}.
@end deffn

@end deffn

@deffn {Interface Driver} {imx_gpio}
i.MX SoC is present in many community boards. Wandboard is an example
of the one which is most popular.

This driver is mostly the same as bcm2835gpio.

See @file{interface/imx-native.cfg} for a sample config and
pinout.

@end deffn


@deffn {Interface Driver} {am335xgpio} The AM335x SoC is present in BeagleBone
Black and BeagleBone Green single-board computers which expose some of the GPIOs
on the two expansion headers.

For maximum performance the driver accesses memory-mapped GPIO peripheral
registers directly. The memory mapping requires read and write permission to
kernel memory; if /dev/gpiomem exists it will be used, otherwise /dev/mem will
be used. The driver restores the GPIO state on exit.

All four GPIO ports are available. GPIOs numbered 0 to 31 are mapped to GPIO port
0, GPIO numbers 32 to 63 are mapped to GPIO port 1 and so on.

See @file{interface/beaglebone-swd-native.cfg} for a sample configuration file.

@deffn {Config Command} {am335xgpio jtag_nums} @var{tck} @var{tms} @var{tdi} @var{tdo}
Set JTAG transport GPIO numbers for TCK, TMS, TDI, and TDO (in that order).
Must be specified to enable JTAG transport. These pins can also be specified
individually.
@end deffn

@deffn {Config Command} {am335xgpio tck_num} @var{tck}
Set TCK GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{am335xgpio jtag_nums}.
@end deffn

@deffn {Config Command} {am335xgpio tms_num} @var{tms}
Set TMS GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{am335xgpio jtag_nums}.
@end deffn

@deffn {Config Command} {am335xgpio tdo_num} @var{tdo}
Set TDO GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{am335xgpio jtag_nums}.
@end deffn

@deffn {Config Command} {am335xgpio tdi_num} @var{tdi}
Set TDI GPIO number. Must be specified to enable JTAG transport. Can also be
specified using the configuration command @command{am335xgpio jtag_nums}.
@end deffn

@deffn {Config Command} {am335xgpio swd_nums} @var{swclk} @var{swdio}
Set SWD transport GPIO numbers for SWCLK and SWDIO (in that order). Must be
specified to enable SWD transport. These pins can also be specified individually.
@end deffn

@deffn {Config Command} {am335xgpio swclk_num} @var{swclk}
Set SWCLK GPIO number. Must be specified to enable SWD transport. Can also be
specified using the configuration command @command{am335xgpio swd_nums}.
@end deffn

@deffn {Config Command} {am335xgpio swdio_num} @var{swdio}
Set SWDIO GPIO number. Must be specified to enable SWD transport. Can also be
specified using the configuration command @command{am335xgpio swd_nums}.
@end deffn

@deffn {Config Command} {am335xgpio swdio_dir_num} @var{swdio_dir}
Set SWDIO direction control pin GPIO number. If specified, this pin can be used
to control the direction of an external buffer on the SWDIO pin. The direction
control state can be set with the command @command{am335xgpio
swdio_dir_output_state}. If not specified this feature is disabled.
@end deffn

@deffn {Config Command} {am335xgpio swdio_dir_output_state} @var{output_state}
Set the state required for an external SWDIO buffer to be an output. Valid
values are @option{on} (default) and @option{off}.
@end deffn

@deffn {Config Command} {am335xgpio srst_num} @var{srst}
Set SRST GPIO number. Must be specified to enable SRST.
@end deffn

@deffn {Config Command} {am335xgpio trst_num} @var{trst}
Set TRST GPIO number. Must be specified to enable TRST.
@end deffn

@deffn {Config Command} {am335xgpio led_num} @var{led}
Set activity LED GPIO number. If not specified an activity LED is not enabled.
@end deffn

@deffn {Config Command} {am335xgpio led_on_state} @var{on_state}
Set required logic level for the LED to be on. Valid values are @option{on}
(default) and @option{off}.
@end deffn

@deffn {Config Command} {am335xgpio speed_coeffs} @var{speed_coeff} @var{speed_offset}
Set SPEED_COEFF and SPEED_OFFSET for delay calculations. If unspecified
speed_coeff defaults to 600000 and speed_offset defaults to 575.
@end deffn

@end deffn


@deffn {Interface Driver} {linuxgpiod}
Linux provides userspace access to GPIO through libgpiod since Linux kernel version v4.6.
The driver emulates either JTAG or SWD transport through bitbanging.

See @file{interface/dln-2-gpiod.cfg} for a sample config.

@deffn {Config Command} {linuxgpiod gpiochip} @var{chip}
Set the GPIO chip number for all GPIOs used by linuxgpiod. If GPIOs use
different GPIO chips then the individual GPIO configuration commands (i.e., not
@command{linuxgpiod jtag_nums} or @command{linuxgpiod swd_nums}) can be used to
set chip numbers independently for each GPIO.
@end deffn

@deffn {Config Command} {linuxgpiod jtag_nums} @var{tck} @var{tms} @var{tdi} @var{tdo}
Set JTAG transport GPIO numbers for TCK, TMS, TDI, and TDO (in that order). Must
be specified to enable JTAG transport. These pins can also be specified
individually.
@end deffn

@deffn {Config Command} {linuxgpiod tck_num} [@var{chip}] @var{tck}
Set TCK GPIO number, and optionally TCK chip number. Must be specified to enable
JTAG transport. Can also be specified using the configuration command
@command{linuxgpiod jtag_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod tms_num} [@var{chip}] @var{tms}
Set TMS GPIO number, and optionally TMS chip number. Must be specified to enable
JTAG transport. Can also be specified using the configuration command
@command{linuxgpiod jtag_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod tdo_num} [@var{chip}] @var{tdo}
Set TDO GPIO number, and optionally TDO chip number. Must be specified to enable
JTAG transport. Can also be specified using the configuration command
@command{linuxgpiod jtag_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod tdi_num} [@var{chip}] @var{tdi}
Set TDI GPIO number, and optionally TDI chip number. Must be specified to enable
JTAG transport. Can also be specified using the configuration command
@command{linuxgpiod jtag_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod trst_num} [@var{chip}] @var{trst}
Set TRST GPIO number, and optionally TRST chip number. Must be specified to
enable TRST.
@end deffn

@deffn {Config Command} {linuxgpiod swd_nums} @var{swclk} @var{swdio}
Set SWD transport GPIO numbers for SWCLK and SWDIO (in that order). Must be
specified to enable SWD transport. These pins can also be specified
individually.
@end deffn

@deffn {Config Command} {linuxgpiod swclk_num} [@var{chip}] @var{swclk}
Set SWCLK GPIO number, and optionally SWCLK chip number. Must be specified to
enable SWD transport. Can also be specified using the configuration command
@command{linuxgpiod swd_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod swdio_num} [@var{chip}] @var{swdio}
Set SWDIO GPIO number, and optionally SWDIO chip number. Must be specified to
enable SWD transport. Can also be specified using the configuration command
@command{linuxgpiod swd_nums}.
@end deffn

@deffn {Config Command} {linuxgpiod swdio_dir_num} [@var{chip}] @var{swdio_dir}
Set SWDIO direction control GPIO number, and optionally SWDIO direction control
chip number. If specified, this GPIO can be used to control the direction of an
external buffer connected to the SWDIO GPIO (set=output mode, clear=input mode).
@end deffn

@deffn {Config Command} {linuxgpiod srst_num} [@var{chip}] @var{srst}
Set SRST GPIO number, and optionally SRST chip number. Must be specified to
enable SRST.
@end deffn

@deffn {Config Command} {linuxgpiod led_num} [@var{chip}] @var{led}
Set activity LED GPIO number, and optionally activity LED chip number. If not
specified an activity LED is not enabled.
@end deffn

@end deffn


@deffn {Interface Driver} {sysfsgpio}
Linux legacy userspace access to GPIO through sysfs is deprecated from Linux kernel version v5.3.
Prefer using @b{linuxgpiod}, instead.

See @file{interface/sysfsgpio-raspberrypi.cfg} for a sample config.
@end deffn


@deffn {Interface Driver} {openjtag}
OpenJTAG compatible USB adapter.
This defines some driver-specific commands:

@deffn {Config Command} {openjtag variant} variant
Specifies the variant of the OpenJTAG adapter (see @uref{http://www.openjtag.org/}).
Currently valid @var{variant} values include:

@itemize @minus
@item @b{standard} Standard variant (default).
@item @b{cy7c65215} Cypress CY7C65215 Dual Channel USB-Serial Bridge Controller
(see @uref{http://www.cypress.com/?rID=82870}).
@end itemize
@end deffn

@deffn {Config Command} {openjtag device_desc} string
The USB device description string of the adapter.
This value is only used with the standard variant.
@end deffn
@end deffn


@deffn {Interface Driver} {vdebug}
Cadence Virtual Debug Interface driver.

@deffn {Config Command} {vdebug server} host:port
Specifies the host and TCP port number where the vdebug server runs.
@end deffn

@deffn {Config Command} {vdebug batching} value
Specifies the batching method for the vdebug request. Possible values are
0 for no batching
1 or wr to batch write transactions together (default)
2 or rw to batch both read and write transactions
@end deffn

@deffn {Config Command} {vdebug polling} min max
Takes two values, representing the polling interval in ms. Lower values mean faster
debugger responsiveness, but lower emulation performance. The minimum should be
around 10, maximum should not exceed 1000, which is the default gdb and keepalive
timeout value.
@end deffn

@deffn {Config Command} {vdebug bfm_path} path clk_period
Specifies the hierarchical path and input clk period of the vdebug BFM in the design.
The hierarchical path uses Verilog notation top.inst.inst
The clock period must include the unit, for instance 40ns.
@end deffn

@deffn {Config Command} {vdebug mem_path} path base size
Specifies the hierarchical path to the design memory instance for backdoor access.
Up to 4 memories can be specified. The hierarchical path uses Verilog notation.
The base specifies start address in the design address space, size its size in bytes.
Both values can use hexadecimal notation with prefix 0x.
@end deffn
@end deffn

@deffn {Interface Driver} {jtag_dpi}
SystemVerilog Direct Programming Interface (DPI) compatible driver for
JTAG devices in emulation. The driver acts as a client for the SystemVerilog
DPI server interface.

@deffn {Config Command} {jtag_dpi set_port} port
Specifies the TCP/IP port number of the SystemVerilog DPI server interface.
@end deffn

@deffn {Config Command} {jtag_dpi set_address} address
Specifies the TCP/IP address of the SystemVerilog DPI server interface.
@end deffn
@end deffn


@deffn {Interface Driver} {buspirate}

This driver is for the Bus Pirate (see @url{http://dangerousprototypes.com/docs/Bus_Pirate}) and compatible devices.
It uses a simple data protocol over a serial port connection.

Most hardware development boards have a UART, a real serial port, or a virtual USB serial device, so this driver
allows you to start building your own JTAG adapter without the complexity of a custom USB connection.

@deffn {Config Command} {buspirate port} serial_port
Specify the serial port's filename. For example:
@example
buspirate port /dev/ttyUSB0
@end example
@end deffn

@deffn {Config Command} {buspirate speed} (normal|fast)
Set the communication speed to 115k (normal) or 1M (fast). For example:
@example
buspirate speed normal
@end example
@end deffn

@deffn {Config Command} {buspirate mode} (normal|open-drain)
Set the Bus Pirate output mode.
@itemize @minus
@item In normal mode (push/pull), do not enable the pull-ups, and do not connect I/O header pin VPU to JTAG VREF.
@item In open drain mode, you will then need to enable the pull-ups.
@end itemize
For example:
@example
buspirate mode normal
@end example
@end deffn

@deffn {Config Command} {buspirate pullup} (0|1)
Whether to connect (1) or not (0) the I/O header pin VPU (JTAG VREF)
to the pull-up/pull-down resistors on MOSI (JTAG TDI), CLK (JTAG TCK), MISO (JTAG TDO) and CS (JTAG TMS).
For example:
@example
buspirate pullup 0
@end example
@end deffn

@deffn {Config Command} {buspirate vreg} (0|1)
Whether to enable (1) or disable (0) the built-in voltage regulator,
which can be used to supply power to a test circuit through
I/O header pins +3V3 and +5V. For example:
@example
buspirate vreg 0
@end example
@end deffn

@deffn {Command} {buspirate led} (0|1)
Turns the Bus Pirate's LED on (1) or off (0). For example:
@end deffn
@example
buspirate led 1
@end example

@end deffn


@section Transport Configuration
@cindex Transport
As noted earlier, depending on the version of OpenOCD you use,
and the debug adapter you are using,
several transports may be available to
communicate with debug targets (or perhaps to program flash memory).
@deffn {Command} {transport list}
displays the names of the transports supported by this
version of OpenOCD.
@end deffn

@deffn {Command} {transport select} @option{transport_name}
Select which of the supported transports to use in this OpenOCD session.

When invoked with @option{transport_name}, attempts to select the named
transport.  The transport must be supported by the debug adapter
hardware and by the version of OpenOCD you are using (including the
adapter's driver).

If no transport has been selected and no @option{transport_name} is
provided, @command{transport select} auto-selects the first transport
supported by the debug adapter.

@command{transport select} always returns the name of the session's selected
transport, if any.
@end deffn

@subsection JTAG Transport
@cindex JTAG
JTAG is the original transport supported by OpenOCD, and most
of the OpenOCD commands support it.
JTAG transports expose a chain of one or more Test Access Points (TAPs),
each of which must be explicitly declared.
JTAG supports both debugging and boundary scan testing.
Flash programming support is built on top of debug support.

JTAG transport is selected with the command @command{transport select
jtag}. Unless your adapter uses either @ref{hla_interface,the hla interface
driver} (in which case the command is @command{transport select hla_jtag})
or @ref{st_link_dap_interface,the st-link interface driver} (in which case
the command is @command{transport select dapdirect_jtag}).

@subsection SWD Transport
@cindex SWD
@cindex Serial Wire Debug
SWD (Serial Wire Debug) is an ARM-specific transport which exposes one
Debug Access Point (DAP, which must be explicitly declared.
(SWD uses fewer signal wires than JTAG.)
SWD is debug-oriented, and does not support boundary scan testing.
Flash programming support is built on top of debug support.
(Some processors support both JTAG and SWD.)

SWD transport is selected with the command @command{transport select
swd}. Unless your adapter uses either @ref{hla_interface,the hla interface
driver} (in which case the command is @command{transport select hla_swd})
or @ref{st_link_dap_interface,the st-link interface driver} (in which case
the command is @command{transport select dapdirect_swd}).

@deffn {Config Command} {swd newdap} ...
Declares a single DAP which uses SWD transport.
Parameters are currently the same as "jtag newtap" but this is
expected to change.
@end deffn

@cindex SWD multi-drop
The newer SWD devices (SW-DP v2 or SWJ-DP v2) support the multi-drop extension
of SWD protocol: two or more devices can be connected to one SWD adapter.
SWD transport works in multi-drop mode if @ref{dap_create,DAP} is configured
with both @code{-dp-id} and @code{-instance-id} parameters regardless how many
DAPs are created.

Not all adapters and adapter drivers support SWD multi-drop. Only the following
adapter drivers are SWD multi-drop capable:
cmsis_dap (use an adapter with CMSIS-DAP version 2.0), ftdi, all bitbang based.

@subsection SPI Transport
@cindex SPI
@cindex Serial Peripheral Interface
The Serial Peripheral Interface (SPI) is a general purpose transport
which uses four wire signaling. Some processors use it as part of a
solution for flash programming.

@anchor{swimtransport}
@subsection SWIM Transport
@cindex SWIM
@cindex Single Wire Interface Module
The Single Wire Interface Module (SWIM) is a low-pin-count debug protocol used
by the STMicroelectronics MCU family STM8 and documented in the
@uref{https://www.st.com/resource/en/user_manual/cd00173911.pdf, User Manual UM470}.

SWIM does not support boundary scan testing nor multiple cores.

The SWIM transport is selected with the command @command{transport select swim}.

The concept of TAPs does not fit in the protocol since SWIM does not implement
a scan chain. Nevertheless, the current SW model of OpenOCD requires defining a
virtual SWIM TAP through the command @command{swim newtap basename tap_type}.
The TAP definition must precede the target definition command
@command{target create target_name stm8 -chain-position basename.tap_type}.

@anchor{jtagspeed}
@section JTAG Speed
JTAG clock setup is part of system setup.
It @emph{does not belong with interface setup} since any interface
only knows a few of the constraints for the JTAG clock speed.
Sometimes the JTAG speed is
changed during the target initialization process: (1) slow at
reset, (2) program the CPU clocks, (3) run fast.
Both the "slow" and "fast" clock rates are functions of the
oscillators used, the chip, the board design, and sometimes
power management software that may be active.

The speed used during reset, and the scan chain verification which
follows reset, can be adjusted using a @code{reset-start}
target event handler.
It can then be reconfigured to a faster speed by a
@code{reset-init} target event handler after it reprograms those
CPU clocks, or manually (if something else, such as a boot loader,
sets up those clocks).
@xref{targetevents,,Target Events}.
When the initial low JTAG speed is a chip characteristic, perhaps
because of a required oscillator speed, provide such a handler
in the target config file.
When that speed is a function of a board-specific characteristic
such as which speed oscillator is used, it belongs in the board
config file instead.
In both cases it's safest to also set the initial JTAG clock rate
to that same slow speed, so that OpenOCD never starts up using a
clock speed that's faster than the scan chain can support.

@example
jtag_rclk 3000
$_TARGET.cpu configure -event reset-start @{ jtag_rclk 3000 @}
@end example

If your system supports adaptive clocking (RTCK), configuring
JTAG to use that is probably the most robust approach.
However, it introduces delays to synchronize clocks; so it
may not be the fastest solution.

@b{NOTE:} Script writers should consider using @command{jtag_rclk}
instead of @command{adapter speed}, but only for (ARM) cores and boards
which support adaptive clocking.

@deffn {Command} {adapter speed} max_speed_kHz
A non-zero speed is in KHZ. Hence: 3000 is 3mhz.
JTAG interfaces usually support a limited number of
speeds. The speed actually used won't be faster
than the speed specified.

Chip data sheets generally include a top JTAG clock rate.
The actual rate is often a function of a CPU core clock,
and is normally less than that peak rate.
For example, most ARM cores accept at most one sixth of the CPU clock.

Speed 0 (khz) selects RTCK method.
@xref{faqrtck,,FAQ RTCK}.
If your system uses RTCK, you won't need to change the
JTAG clocking after setup.
Not all interfaces, boards, or targets support ``rtck''.
If the interface device can not
support it, an error is returned when you try to use RTCK.
@end deffn

@defun jtag_rclk fallback_speed_kHz
@cindex adaptive clocking
@cindex RTCK
This Tcl proc (defined in @file{startup.tcl}) attempts to enable RTCK/RCLK.
If that fails (maybe the interface, board, or target doesn't
support it), falls back to the specified frequency.
@example
# Fall back to 3mhz if RTCK is not supported
jtag_rclk 3000
@end example
@end defun

@node Reset Configuration
@chapter Reset Configuration
@cindex Reset Configuration

Every system configuration may require a different reset
configuration. This can also be quite confusing.
Resets also interact with @var{reset-init} event handlers,
which do things like setting up clocks and DRAM, and
JTAG clock rates. (@xref{jtagspeed,,JTAG Speed}.)
They can also interact with JTAG routers.
Please see the various board files for examples.

@quotation Note
To maintainers and integrators:
Reset configuration touches several things at once.
Normally the board configuration file
should define it and assume that the JTAG adapter supports
everything that's wired up to the board's JTAG connector.

However, the target configuration file could also make note
of something the silicon vendor has done inside the chip,
which will be true for most (or all) boards using that chip.
And when the JTAG adapter doesn't support everything, the
user configuration file will need to override parts of
the reset configuration provided by other files.
@end quotation

@section Types of Reset

There are many kinds of reset possible through JTAG, but
they may not all work with a given board and adapter.
That's part of why reset configuration can be error prone.

@itemize @bullet
@item
@emph{System Reset} ... the @emph{SRST} hardware signal
resets all chips connected to the JTAG adapter, such as processors,
power management chips, and I/O controllers. Normally resets triggered
with this signal behave exactly like pressing a RESET button.
@item
@emph{JTAG TAP Reset} ... the @emph{TRST} hardware signal resets
just the TAP controllers connected to the JTAG adapter.
Such resets should not be visible to the rest of the system; resetting a
device's TAP controller just puts that controller into a known state.
@item
@emph{Emulation Reset} ... many devices can be reset through JTAG
commands. These resets are often distinguishable from system
resets, either explicitly (a "reset reason" register says so)
or implicitly (not all parts of the chip get reset).
@item
@emph{Other Resets} ... system-on-chip devices often support
several other types of reset.
You may need to arrange that a watchdog timer stops
while debugging, preventing a watchdog reset.
There may be individual module resets.
@end itemize

In the best case, OpenOCD can hold SRST, then reset
the TAPs via TRST and send commands through JTAG to halt the
CPU at the reset vector before the 1st instruction is executed.
Then when it finally releases the SRST signal, the system is
halted under debugger control before any code has executed.
This is the behavior required to support the @command{reset halt}
and @command{reset init} commands; after @command{reset init} a
board-specific script might do things like setting up DRAM.
(@xref{resetcommand,,Reset Command}.)

@anchor{srstandtrstissues}
@section SRST and TRST Issues

Because SRST and TRST are hardware signals, they can have a
variety of system-specific constraints. Some of the most
common issues are:

@itemize @bullet

@item @emph{Signal not available} ... Some boards don't wire
SRST or TRST to the JTAG connector. Some JTAG adapters don't
support such signals even if they are wired up.
Use the @command{reset_config} @var{signals} options to say
when either of those signals is not connected.
When SRST is not available, your code might not be able to rely
on controllers having been fully reset during code startup.
Missing TRST is not a problem, since JTAG-level resets can
be triggered using with TMS signaling.

@item @emph{Signals shorted} ... Sometimes a chip, board, or
adapter will connect SRST to TRST, instead of keeping them separate.
Use the @command{reset_config} @var{combination} options to say
when those signals aren't properly independent.

@item @emph{Timing} ... Reset circuitry like a resistor/capacitor
delay circuit, reset supervisor, or on-chip features can extend
the effect of a JTAG adapter's reset for some time after the adapter
stops issuing the reset. For example, there may be chip or board
requirements that all reset pulses last for at least a
certain amount of time; and reset buttons commonly have
hardware debouncing.
Use the @command{adapter srst delay} and @command{jtag_ntrst_delay}
commands to say when extra delays are needed.

@item @emph{Drive type} ... Reset lines often have a pullup
resistor, letting the JTAG interface treat them as open-drain
signals. But that's not a requirement, so the adapter may need
to use push/pull output drivers.
Also, with weak pullups it may be advisable to drive
signals to both levels (push/pull) to minimize rise times.
Use the @command{reset_config} @var{trst_type} and
@var{srst_type} parameters to say how to drive reset signals.

@item @emph{Special initialization} ... Targets sometimes need
special JTAG initialization sequences to handle chip-specific
issues (not limited to errata).
For example, certain JTAG commands might need to be issued while
the system as a whole is in a reset state (SRST active)
but the JTAG scan chain is usable (TRST inactive).
Many systems treat combined assertion of SRST and TRST as a
trigger for a harder reset than SRST alone.
Such custom reset handling is discussed later in this chapter.
@end itemize

There can also be other issues.
Some devices don't fully conform to the JTAG specifications.
Trivial system-specific differences are common, such as
SRST and TRST using slightly different names.
There are also vendors who distribute key JTAG documentation for
their chips only to developers who have signed a Non-Disclosure
Agreement (NDA).

Sometimes there are chip-specific extensions like a requirement to use
the normally-optional TRST signal (precluding use of JTAG adapters which
don't pass TRST through), or needing extra steps to complete a TAP reset.

In short, SRST and especially TRST handling may be very finicky,
needing to cope with both architecture and board specific constraints.

@section Commands for Handling Resets

@deffn {Command} {adapter srst pulse_width} milliseconds
Minimum amount of time (in milliseconds) OpenOCD should wait
after asserting nSRST (active-low system reset) before
allowing it to be deasserted.
@end deffn

@deffn {Command} {adapter srst delay} milliseconds
How long (in milliseconds) OpenOCD should wait after deasserting
nSRST (active-low system reset) before starting new JTAG operations.
When a board has a reset button connected to SRST line it will
probably have hardware debouncing, implying you should use this.
@end deffn

@deffn {Command} {jtag_ntrst_assert_width} milliseconds
Minimum amount of time (in milliseconds) OpenOCD should wait
after asserting nTRST (active-low JTAG TAP reset) before
allowing it to be deasserted.
@end deffn

@deffn {Command} {jtag_ntrst_delay} milliseconds
How long (in milliseconds) OpenOCD should wait after deasserting
nTRST (active-low JTAG TAP reset) before starting new JTAG operations.
@end deffn

@anchor{reset_config}
@deffn {Command} {reset_config} mode_flag ...
This command displays or modifies the reset configuration
of your combination of JTAG board and target in target
configuration scripts.

Information earlier in this section describes the kind of problems
the command is intended to address (@pxref{srstandtrstissues,,SRST and TRST Issues}).
As a rule this command belongs only in board config files,
describing issues like @emph{board doesn't connect TRST};
or in user config files, addressing limitations derived
from a particular combination of interface and board.
(An unlikely example would be using a TRST-only adapter
with a board that only wires up SRST.)

The @var{mode_flag} options can be specified in any order, but only one
of each type -- @var{signals}, @var{combination}, @var{gates},
@var{trst_type}, @var{srst_type} and @var{connect_type}
-- may be specified at a time.
If you don't provide a new value for a given type, its previous
value (perhaps the default) is unchanged.
For example, this means that you don't need to say anything at all about
TRST just to declare that if the JTAG adapter should want to drive SRST,
it must explicitly be driven high (@option{srst_push_pull}).

@itemize
@item
@var{signals} can specify which of the reset signals are connected.
For example, If the JTAG interface provides SRST, but the board doesn't
connect that signal properly, then OpenOCD can't use it.
Possible values are @option{none} (the default), @option{trst_only},
@option{srst_only} and @option{trst_and_srst}.

@quotation Tip
If your board provides SRST and/or TRST through the JTAG connector,
you must declare that so those signals can be used.
@end quotation

@item
The @var{combination} is an optional value specifying broken reset
signal implementations.
The default behaviour if no option given is @option{separate},
indicating everything behaves normally.
@option{srst_pulls_trst} states that the
test logic is reset together with the reset of the system (e.g. NXP
LPC2000, "broken" board layout), @option{trst_pulls_srst} says that
the system is reset together with the test logic (only hypothetical, I
haven't seen hardware with such a bug, and can be worked around).
@option{combined} implies both @option{srst_pulls_trst} and
@option{trst_pulls_srst}.

@item
The @var{gates} tokens control flags that describe some cases where
JTAG may be unavailable during reset.
@option{srst_gates_jtag} (default)
indicates that asserting SRST gates the
JTAG clock. This means that no communication can happen on JTAG
while SRST is asserted.
Its converse is @option{srst_nogate}, indicating that JTAG commands
can safely be issued while SRST is active.

@item
The @var{connect_type} tokens control flags that describe some cases where
SRST is asserted while connecting to the target. @option{srst_nogate}
is required to use this option.
@option{connect_deassert_srst} (default)
indicates that SRST will not be asserted while connecting to the target.
Its converse is @option{connect_assert_srst}, indicating that SRST will
be asserted before any target connection.
Only some targets support this feature, STM32 and STR9 are examples.
This feature is useful if you are unable to connect to your target due
to incorrect options byte config or illegal program execution.
@end itemize

The optional @var{trst_type} and @var{srst_type} parameters allow the
driver mode of each reset line to be specified. These values only affect
JTAG interfaces with support for different driver modes, like the Amontec
JTAGkey and JTAG Accelerator. Also, they are necessarily ignored if the
relevant signal (TRST or SRST) is not connected.

@itemize
@item
Possible @var{trst_type} driver modes for the test reset signal (TRST)
are the default @option{trst_push_pull}, and @option{trst_open_drain}.
Most boards connect this signal to a pulldown, so the JTAG TAPs
never leave reset unless they are hooked up to a JTAG adapter.

@item
Possible @var{srst_type} driver modes for the system reset signal (SRST)
are the default @option{srst_open_drain}, and @option{srst_push_pull}.
Most boards connect this signal to a pullup, and allow the
signal to be pulled low by various events including system
power-up and pressing a reset button.
@end itemize
@end deffn

@section Custom Reset Handling
@cindex events

OpenOCD has several ways to help support the various reset
mechanisms provided by chip and board vendors.
The commands shown in the previous section give standard parameters.
There are also @emph{event handlers} associated with TAPs or Targets.
Those handlers are Tcl procedures you can provide, which are invoked
at particular points in the reset sequence.

@emph{When SRST is not an option} you must set
up a @code{reset-assert} event handler for your target.
For example, some JTAG adapters don't include the SRST signal;
and some boards have multiple targets, and you won't always
want to reset everything at once.

After configuring those mechanisms, you might still
find your board doesn't start up or reset correctly.
For example, maybe it needs a slightly different sequence
of SRST and/or TRST manipulations, because of quirks that
the @command{reset_config} mechanism doesn't address;
or asserting both might trigger a stronger reset, which
needs special attention.

Experiment with lower level operations, such as
@command{adapter assert}, @command{adapter deassert}
and the @command{jtag arp_*} operations shown here,
to find a sequence of operations that works.
@xref{JTAG Commands}.
When you find a working sequence, it can be used to override
@command{jtag_init}, which fires during OpenOCD startup
(@pxref{configurationstage,,Configuration Stage});
or @command{init_reset}, which fires during reset processing.

You might also want to provide some project-specific reset
schemes. For example, on a multi-target board the standard
@command{reset} command would reset all targets, but you
may need the ability to reset only one target at time and
thus want to avoid using the board-wide SRST signal.

@deffn {Overridable Procedure} {init_reset} mode
This is invoked near the beginning of the @command{reset} command,
usually to provide as much of a cold (power-up) reset as practical.
By default it is also invoked from @command{jtag_init} if
the scan chain does not respond to pure JTAG operations.
The @var{mode} parameter is the parameter given to the
low level reset command (@option{halt},
@option{init}, or @option{run}), @option{setup},
or potentially some other value.

The default implementation just invokes @command{jtag arp_init-reset}.
Replacements will normally build on low level JTAG
operations such as @command{adapter assert} and @command{adapter deassert}.
Operations here must not address individual TAPs
(or their associated targets)
until the JTAG scan chain has first been verified to work.

Implementations must have verified the JTAG scan chain before
they return.
This is done by calling @command{jtag arp_init}
(or @command{jtag arp_init-reset}).
@end deffn

@deffn {Command} {jtag arp_init}
This validates the scan chain using just the four
standard JTAG signals (TMS, TCK, TDI, TDO).
It starts by issuing a JTAG-only reset.
Then it performs checks to verify that the scan chain configuration
matches the TAPs it can observe.
Those checks include checking IDCODE values for each active TAP,
and verifying the length of their instruction registers using
TAP @code{-ircapture} and @code{-irmask} values.
If these tests all pass, TAP @code{setup} events are
issued to all TAPs with handlers for that event.
@end deffn

@deffn {Command} {jtag arp_init-reset}
This uses TRST and SRST to try resetting
everything on the JTAG scan chain
(and anything else connected to SRST).
It then invokes the logic of @command{jtag arp_init}.
@end deffn


@node TAP Declaration
@chapter TAP Declaration
@cindex TAP declaration
@cindex TAP configuration

@emph{Test Access Ports} (TAPs) are the core of JTAG.
TAPs serve many roles, including: