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RIOT/cpu/kinetis_common/periph/wdog.c 1.95 KB
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  /*
   * Copyright (C) 2015 PHYTEC Messtechnik GmbH
   * Copyright (C) 2015 Eistec AB
   *
   * This file is subject to the terms and conditions of the GNU Lesser General
   * Public License v2.1. See the file LICENSE in the top level directory for more
   * details.
   */
  
  /**
   * @ingroup     cpu_kinetis_common_wdog
   *
   * @{
   *
   * @file
   * @brief       Low-level WDOG driver implementation
   *
   * @author      Johann Fischer <j.fischer@phytec.de>
   * @author      Joakim Nohlgård <joakim.nohlgard@eistec.se>
   *
   * @}
   */
  
  #include <stdint.h>
  #include "wdog.h"
  #include "cpu_conf.h"
  #include "periph_conf.h"
  
  #ifndef KINETIS_WDOG_ADVANCED
  /**
   * Attempts to determine the type of the WDOG,
   * using the WDOG_STCTRLH_CLKSRC_MASK field.
   */
  #ifdef WDOG_STCTRLH_CLKSRC_MASK
  #define KINETIS_WDOG_ADVANCED    1
  #endif
  #endif
  
  /**
   * @brief Disable hardware watchdog.
   *
   * For advanced WDOG (mostly Kinetis MCUs with Cortex-M4 inside):
   * The following unlock sequence must be completed within 256 bus cycles or
   * the watchdog will reset the system. The watchdog is enabled by default at
   * power on.
   *
   * The sequence is:
   * 1. Write 0xC520 to the unlock register
   * 2. Write 0xD928 to the unlock register
   *
   * Watchdog is now unlocked to allow us to change its settings
   *
   * 3. Clear the WDOGEN bit of the WDOG_STCTRLH register to completely disable
   * the watchdog.
   *
   * It is now possible to single step through the code without the watchdog
   * resetting the system.
   *
   * TODO: Only disable watchdog on debug builds.
   */
  void wdog_disable(void)
  {
  #if KINETIS_WDOG_ADVANCED
      /* unlock and disable the WDOG */
      WDOG->UNLOCK = (uint16_t)0xc520;
      WDOG->UNLOCK = (uint16_t)0xd928;
      WDOG->STCTRLH = (uint16_t)(WDOG_STCTRLH_WAITEN_MASK
                                 | WDOG_STCTRLH_STOPEN_MASK
                                 | WDOG_STCTRLH_ALLOWUPDATE_MASK
                                 | WDOG_STCTRLH_CLKSRC_MASK);
  #else
      /* disable the COP WDOG */
      SIM->COPC = (uint32_t)0x00u;
  #endif
  }