STM8L探索套件学习笔记-独立看门狗IWDG（十六）

STM8L 的独立看门狗由内部专门的 38Khz 低速时钟驱动，即使主时钟发生故障，它也仍然有效。这里需要注意独立看门狗的时钟并不是准确的 38Khz，只是我们在估算的时候，以 38Khz 的频率来计算，看门狗对时间的要求不是很精确，所以，时钟有些偏差，都是可以接受的。根据分频系统和看门狗计数值可以设置独立看门狗的复位时间，范围从0.1ms~1724.63ms

例程展示如何重载IWDG计数值，IWDG的时间设置为214.7ms。程序采用“Refresh”变量来使能IWDG重载计数值仿真IWDG复位，并且板上LED4翻转。当按键按下，模拟一次软件错误造成程序没有喂狗，从而发生复位。如果IWDG复位，系统启动后LED3会翻转8次，主代码如下：

void main(void)

{

uint8_t Index;

GPIO_Init(LED3_PORT,LED3_PIN,GPIO_Mode_Out_PP_Low_Fast);

//输出低电平-高速10M

GPIO_Init(LED4_PORT,LED4_PIN,GPIO_Mode_Out_PP_Low_Fast);

//输出低电平-高速10M

GPIO_Init(KEY_PORT,KEY_PIN,GPIO_Mode_In_FL_IT);

//输入浮空-中断

/* Set PC1 sensitivity to falling edge and low level 下降沿低电平触发*/

EXTI_SetPinSensitivity(EXTI_Pin_1, EXTI_Trigger_Falling_Low);

/* Check if the MCU has resumed from IWDG reset */

if (RST_GetFlagStatus(RST_FLAG_IWDGF) != RESET)

{

/* IWDGF flag set */

/* Toggle LED3 */

for (Index = 7; Index != 0; Index--)

{

GPIO_ToggleBits(LED3_PORT,LED3_PIN);

Delay(0x7FFF);

}

/* Clear IWDGF Flag */

RST_ClearFlag(RST_FLAG_IWDGF);

}

/* IWDG configuration: IWDG is clocked by LSI = 38KHz */

/* IWDG timeout equal to 214.7 ms (the timeout may varies due to LSI frequency dispersion) */

/* IWDG timeout = (RELOAD_VALUE + 1) * Prescaler / LSI = (254 + 1) * 32 / 38 000 = 214.7 ms */

/* Enable the IWDG */

IWDG_Enable();

/* Enable write access to IWDG_PR and IWDG_RLR registers */

IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);

/* Set IWDG timeout */

IWDG_SetPrescaler(IWDG_Prescaler_32);

IWDG_SetReload(RELOAD_VALUE);

/* Refresh IWDG */

IWDG_ReloadCounter();

/* enable interrupts by switching to level 0 */

enableInterrupts();

while (1)

{

/* As Refresh is equal to ENABLE no IWDG reset will occur. When Refresh is

equal to DISABLE, the IWDG counter isnt refreshed and IWDG reset will occur. */

if (Refresh != 0)

{

/* Reload IWDG counter */

IWDG_ReloadCounter();

}

/* Toggle LED4 */

GPIO_ToggleBits(LED4_PORT,LED4_PIN);

Delay(0x6FFF);

}

}