contrib/loaders/watchdog/armv7m_kinetis_wdog.s

   1 /***************************************************************************
   2  *   Copyright (C) 2015 Tomas Vanek                                        *
   3  *   vanekt@fbl.cz                                                         *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15  *   You should have received a copy of the GNU General Public License     *
  16  *   along with this program; if not, write to the                         *
  17  *   Free Software Foundation, Inc.                                        *
  18  ***************************************************************************/
  19
  20 /*
  21         Disable watchdog for Kinetis Kx and KVx
  22         Parameters: none
  23         Used instruction set should work on both Cortex-M4 and M0+
  24 */
  25
  26         .text
  27         .syntax unified
  28         .cpu cortex-m0
  29         .thumb
  30
  31 WDOG_ADDR       = 0x40052000
  32 /* WDOG registers offsets */
  33 WDOG_STCTRLH    = 0
  34 WDOG_UNLOCK     = 0x0e
  35
  36 WDOG_KEY1       = 0xc520
  37 WDOG_KEY2       = 0xd928
  38
  39         .thumb_func
  40 start:
  41 /* WDOG_UNLOCK = 0xC520 */
  42         ldr     r3, =WDOG_ADDR
  43         ldr     r2, =WDOG_KEY1
  44         strh    r2, [r3, WDOG_UNLOCK]
  45 /* WDOG_UNLOCK = 0xD928 */
  46         ldr     r2, =WDOG_KEY2
  47         strh    r2, [r3, WDOG_UNLOCK]
  48 /* WDOG_STCTRLH clear bit 0 */
  49         movs    r4, #1
  50         ldrh    r2, [r3, WDOG_STCTRLH]
  51         bics    r2, r4
  52         strh    r2, [r3, WDOG_STCTRLH]
  53 /* OpenOCD checks exit point address. Jump to the very end. */
  54         b       done
  55
  56         .pool
  57
  58 /* Avoid padding at .text segment end. Otherwise exit point check fails. */
  59         .skip   ( . - start + 2) & 2, 0
  60 done:
  61         bkpt    #0
  62
  63         .end
  64