Real Time clock 02

1. Preprocessor Directives:

• #include <pic.h>: Includes the header file pic.h, which contains definitions and declarations specific to PIC microcontrollers.

2. Variable Declarations:

• unsigned char count = 0;: Declares an unsigned character variable count and initializes it to 0. This variable is used to keep track of the number of 50ms intervals that have elapsed.

3. main() Function:

• Initialization:

  • TRISC = 0;: Configures PORTC as output pins.
  • TRISB = 0;: Configures PORTB as output pins.
  • PORTC = 0; PORTB = 0; PORTA = 0;: Clears the output pins on PORTC, PORTB, and PORTA.
  • ADCON1 = 0x07;: Configures the analog-to-digital converter (ADC) module.
  • RA1 = 1; RA2 = 1; RA3 = 1; RA5 = 1;: Activates the common anode segments of the seven-segment display.
  • T0CS = 0;: Selects the internal clock source (Fosc/4) for TMR0.
  • PSA = 0;: Assigns the prescaler to TMR0.
  • PS2 = 1; PS1 = 1; PS0 = 1;: Sets the prescaler to 256, providing a timer tick every 50 milliseconds.
  • TMR0 = 61;: Initializes TMR0 with the value 61 to generate a 50ms delay.
  • RC0 = 1;: Sets the output on RC0.

• Main Loop:

  • while (1) { ... }: The main loop continues indefinitely.
  • Interrupt Handling:
    • if (T0IF) { ... }: Checks if the TMR0 interrupt flag is set.
    • TMR0 = 61;: Reloads TMR0 with the value 61 to start another 50ms delay.
    • count++;: Increments the count variable.
    • if (count == 20) { ... }: Checks if 20 50ms intervals have elapsed (1 second).
      • switch (count) { ... }: Uses a switch statement to select the appropriate seven-segment display pattern based on the current count value.
      • The case statements within the switch block assign the corresponding pattern to PORTB to display the numbers 0, 1, or 2 on the seven-segment display.
      • count = 0;: Resets the count variable to 0.
    • T0IF = 0;: Clears the TMR0 interrupt flag.

Explanation:

The code implements a simple digital counter that displays the numbers 0, 1, and 2 in sequence on a seven-segment display. The main components of the code are:

• Timer Initialization: TMR0 is configured as an internal timer with a prescaler of 256, providing a timer tick every 50 milliseconds.
• Interrupt Handling: The TMR0 interrupt is used to increment a counter and update the display.
• Display Logic: The switch(count) statement controls the seven-segment display outputs based on the current count value.

#include <pic.h>

unsigned char count=0;

void main()

{
TRISC=0;    // PORTC output
PORTC=0;
TRISB=0;    // PORTC output
PORTB=0;
PORTA=0;
PORTA=0;

ADCON1=0x07;
RA1=1;        // digit 1 on
RA2=1;
RA3=1;
RA5=1;
   

T0CS=0;        // Internal Mode (Fosc/4)
PSA=0;        // Prescaler assigned to TMR0
PS2=1;
PS1=1;
PS0=1;   
   
TMR0=61;    // (256-195=61) for 50mS time
RC0=1;        // output on


while(1)   
{
    if(T0IF==1){
    TMR0=61;
    count++;
        if (count==20){
        switch(count)
        {
   
        case 0:
        PORTB=0x3F;
        break;
       
        case 1:
        PORTB=0x06;
        break;
   
        case 2:
        PORTB=0x5B;
        break;
        }

        count=0;
        }
        T0IF=0;
       
}
}

}