System clock and timer - watchdog timer

The watchdog timer is the same as the ordinary timer. However, the ordinary timer usually counts for a period of time, and after the time is up, it enters the interrupt processing program, while the watchdog does not want an interrupt to occur at the end of the defined time. In order to prevent the interrupt from occurring, some registers of the watchdog timer must be reassigned before the interrupt occurs, so that it starts counting again, which is commonly known as the feeding operation.

 The registers involved in the WATCHDOG timer are as follows:

1. WTCON register

Used to set the pre-scaling factor, select the operating frequency, decide whether to enable interrupts, and whether to enable the WATDOG function (i.e., whether to output a reset signal).

WATDOG timer operating frequency = PCLK/(prescaler value+1)/(divider value)

prescaler value = 0 ~ 255;

divider value = 16,32,64,128;

The WTCON in the chip manual is as follows:

 

 

#include "2440addr.h"

#define U32 unsigned int

 

void Delay(int a)

{

       int k;

       for(k=0;k

              ;

}

 

void __irq watchdog(void)

{

     

      rGPBDAT |= 1; /*Buzzer sounds*/

       /* Clear interrupt flag */

/*Pay attention to the following two lines of code. Generally speaking, the interrupt flag clearing order is: SUBSRCPND-->SRCPND-->INTPND. However, when using CodeWarrior to call AXD debugging, there is no interrupt due to the different order. However, when I click the STOP key and then the GO key, I hear a buzzer every time. This phenomenon was discovered later. Is it equivalent to directly generating an interrupt signal after each STOP, resulting in failure to feed the dog normally? I don't quite understand this. I hope someone can explain it to me*/

       rSRCPND = 0x1<<9;

       rSUBSRCPND = 0x1<<13;

       rINTPND = 0x1<<9;
       
      

}

 

void Main(void)

{

       int light;

       int temp;

       int i;

       rGPBCON = 0x155555; /*B0 output, for the buzzer; B5~B8 output, for the LED*/

       rGPBUP = 0x7ff;

 

       rWTCON = 0xf9<<8; /*Set the prescaler coefficient [15:8] and clock selection [4:3]. PCLK=50MHz Prescaler = 15*16+9=249, Division = WTCON[4:3]=0b00=16, the clock frequency is 12.5kHz*/

       rWTDAT = 50000; /*Set the watchdog timer timeout to 4 seconds (50÷12.5)*/

       rWTCNT = 50000;

       rWTCON |= (1<<5)|(1<<2); /*Start the timer [5], enable the interrupt [2], and do not send a reset signal [0]*/

/*Interrupt setting, watchdog has sub-interrupt source*/

       rSRCPND = 0x1<<9;

       rSUBSRCPND = 0x1<<13;

       rINTPND = 0x1<<9;

       rINTSUBMSK = ~(0x1<<13);            

rINTMSK = ~(0x1<<9); 

                  

       pISR_WDT_AC97 = (U32)watchdog;

 

       light = 0x000;

       temp = light | 1;

       rGPBDAT = ~temp;

       Delay(500000); /*About 0.4S delay*/
      

       while(1)

       { 
         
        
         for(i=0;i<4;i++)
         {
                light = 1<<(5+i);

                temp = light | 1;

                rGPBDAT = ~temp;
    Delay(500000);
     if(i>=2)
     {
           light = 1<<(4+2*i);
             temp = light | 1;
      rGPBDAT = ~temp;
      Delay(500000);
     }
          }
  

             rWTCNT = 50000; /*Feed the dog, reassign value, prevent interruption*/
             
           for(i=0;i<4;i++)
         {
                 light = 1>>(5+i);
                 temp = light | 1;
                 rGPBDAT = ~temp;
     Delay(500000);
     if(i>=2)
     {
           light = 1>>(4+2*i);
            temp = light | 1;
      rGPBDAT = ~temp;
      Delay(500000);
     }
          }
 
       }

}