Independent watchdog and window watchdog of stm8

The block diagram of the independent watchdog is as follows

We can see that the clock of the independent watchdog comes from the low-speed oscillator inside LSI, and reaches the watchdog peripheral unit after being divided by two, and then reaches the counter after a seven-bit pre-division. This seven-bit division is controlled by PR. The watchdog uses an eight-bit down-counting counter to count. When the count reaches 0, a watchdog reset signal is issued. At the same time, there is an RLR that can store the initialization value of the watchdog. However, when operating KR, the watchdog counter reloads the data of RLR to achieve the purpose of feeding the dog.

Therefore, the processing of the watchdog should be divided into the following steps

1. Disable the watchdog

2. Start the LSI system low speed clock

3. Set the clock division factor

4. Set the watchdog reload value

5. Feed the dog before resetting and restart the counting

The relevant registers are as follows

See the following code for usage

#ifndef __IWDG_H_
#define __IWDG_H_
#include "stm8s.h"


void IWDGInit(void); //Default count time is one second

void IWDGFeed(void);



#endif

#include "iwdg.h"


void IWDGInit(void) //Default count time is one minute
{
    //First turn on the LSI clock
    CLK->ICKR = (1<<3);
    while((CLK->ICKR&(1<<4)) == 0); //Wait for the clock to stabilize
    IWDG->KR = 0x55; //Write unlock
    IWDG->PR = 0x06; //Division 64K /256 = 250
    IWDG->RLR = 250; //Count value 250 1 reset
    IWDG->KR = 0xaa; //Lock and refresh the divider
    IWDG->KR = 0xcc; //Start independent watchdog
    
}

void IWDGFeed(void)
{
    IWDG->KR = 0xaa; //Lock and refresh the divider
}

Window watchdog is another mode. The chip defines a lower limit, which generates a reset when it is lower than 0x40, and also defines an upper limit. When it is higher than the upper limit, the watchdog also generates a reset.

  The clock of the window watchdog comes from the CPU clock, and the frequency division number is 12288. The process of using the watchdog is as follows

1Set window value

2Set the current count value

3 Start the watchdog

Once the window watchdog is started, it cannot be turned off unless a reset occurs and the system automatically turns off the window watchdog. For specific usage, see the code.

#ifndef __WWDG_H_
#define __WWDG_H_
#include "stm8s.h"


void WWDGInit(void);

void WWDGFeed(void);



#endif

#include "wwdg.h"

void WWDGInit(void)
{
    if((WWDG->CR&0x80) == 1)
    {
        return;
    }
    else
    {
        WWDG->WR = 0x60;
        WWDG->CR = 0xff;
    }
}

void WWDGFeed(void)
{
    u8 windows = WWDG->WR ;
    if((WWDG->CR&0x7f)>=windows)
        return;
    else
         WWDG->CR = 0x7f;
}