timer0 delay differs from calculated value - anything missing?

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bimalkamal

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Please anyone tell me how many times in a minute the LEds of PORTB will blink? Or the delay time the mydelay() will create.

Code C - [expand]
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void mydelay();
 
 
void main() {
  OPTION_REG = 0x87;       // Assign prescaler to TMR0
  TRISB = 0;               // PORTB is output
  PORTB = 0xFF;            // Initialize PORTB
  TMR0  = 0;              // Timer0 initial value
    while(1)
            {
            PORTB = ~PORTB;
            mydelay();
    
            }
  
 
    }
    
 void mydelay()
 {
   unsigned int n=0;
  INTCON.TMR0IE=1;
  do{
  while(!INTCON.TMR0IF);
   n++;
       if(n==76)
   
             { TMR0IE_bit=0;
               n=0;
               INTCON.TMR0IF=0;
               break;
             }
             }while(1);
   }


---------- Post added at 00:21 ---------- Previous post was at 00:16 ----------

Crystal=20Mhz
 

You can achieve a precise answer by some simulation tools.
Take in mind that not only Scaler and Pre-scaler are accounted, but also amount of instructions processed before timer register reload.


+++
 

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