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/*
* Copyright (c) 2014 Wind River Systems, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file
* @brief Watchdog initialization for fsl_frdm_k64f platform
*
* This module initializes the watchdog for the fsl_frdm_k64f platform.
*/
#define _ASMLANGUAGE
#include <soc.h>
#include <toolchain.h>
#include <sections.h>
_ASM_FILE_PROLOGUE
GTEXT(_WdogInit)
/* watchdog register offsets */
#define WDOG_SCTRL_HI_OFFSET 0x0
#define WDOG_UNLOCK_OFFSET 0xE
/* watchdog command words */
#define WDOG_UNLOCK_1_CMD 0xC520
#define WDOG_UNLOCK_2_CMD 0xD928
/**
*
* @brief Watchdog timer disable routine
*
* This routine will disable the watchdog timer.
*
* @return N/A
*/
SECTION_FUNC(TEXT,_WdogInit)
/*
* NOTE: DO NOT SINGLE STEP THROUGH THIS FUNCTION!!!
* There are timing requirements for the execution of the unlock process.
* Single stepping through the code will cause the CPU to reset.
*/
/*
* First unlock the watchdog so that we can write to registers.
*
* This sequence must execute within 20 clock cycles, so disable
* interrupts to keep the code atomic and ensure the timing.
*/
cpsid i
ldr r0, =PERIPH_ADDR_BASE_WDOG
movw r1, #WDOG_UNLOCK_1_CMD
strh r1, [r0, #WDOG_UNLOCK_OFFSET]
movw r1, #WDOG_UNLOCK_2_CMD
strh r1, [r0, #WDOG_UNLOCK_OFFSET]
/*
* Disable the watchdog.
*
* Writes to control/configuration registers must execute within
* 256 clock cycles after unlocking.
*/
ldrh r1, [r0, #WDOG_SCTRL_HI_OFFSET]
mov r2, #1
bics r1, r2
strh r1, [r0, #WDOG_SCTRL_HI_OFFSET]
cpsie i
bx lr
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