PIC_counter.c

  #include "Display_Utils.h"

unsigned short shifter, portb_index;
unsigned int   digit, number;
unsigned short portb_array[4];

void interrupt() {
  PORTA = 0;                             // Turn off all 7seg displays
  PORTB = portb_array[portb_index];      // bring appropriate value to PORTD
  PORTA = shifter;                       // turn on appropriate 7seg. display

  // move shifter to next digit
  shifter <<= 1;
  if (shifter > 8u)
    shifter = 1;

  // increment portd_index
  portb_index++ ;
  if (portb_index > 3u)
    portb_index = 0;             // turn on 1st, turn off 2nd 7seg.
  TMR0L  =   0;                  // reset TIMER0 value
  TMR0IF_bit = 0;                // Clear TMR0IF
}

void main() {

  ADCON1 =0x0F;                      // Configure PORTX pins as digital
  CMCON = 0x07;                     // comparators OFF
  TRISA = 0;                     // Configure PORTA as output
  PORTA  = 0;                     // Clear PORTA
  TRISB = 0;                     // Configure PORTD as output
  PORTB  = 0;                     // Clear PORTD

 T0CON = 0xC4;                  // Set TMR0 in 8bit mode, assign prescaler to TMR0
  TMR0L = 0;                     // clear TMROL
  digit = 0;
  portb_index = 0;
  shifter = 1;

  number = 9980;                 // Initial number value
  GIE_bit = 1;
  TMR0IE_bit = 1;

  do {
    digit = number / 1000u ;             // extract thousands digit
    portb_array[3] = conversion(digit);        // and store it to PORTD array
    digit = (number / 100u) % 10u;       // extract hundreds digit
    portb_array[2] = conversion(digit);        // and store it to PORTD array
    digit = (number / 10u) % 10u;        // extract tens digit
    portb_array[1] = conversion(digit);        // and store it to PORTD array
    digit = number % 10u;                // extract ones digit
    portb_array[0] = conversion(digit);        // and store it to PORTD array

    Delay_ms(400);                      // one second delay

    number++ ;                           // increment number
    if (number > 9999u)
      number = 0;

  } while(1);                            // endless loop
}