PIC16F887 Timer0 Creating Delay Function in MikroC

Introduction

In previous post of Timer0 interrupt programming, we use its interrupt advantage to create a timer tick in a range of milli second. We can decorate some more features over this capability.

A precise timing delay function can be created using timer0 interrupt programming. In this example we create a delay function from the existing 1ms-delay routine that it was written in previous example. 

Program simulation sample

 

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x1.5

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Programming

Delay function created by adding more routine that rely on free running counter in the ISR coding of Timer0 interrupt.

void ms_delay(unsigned count) {
     while(ms_count<count);
      ms_count=0;

}

There is no change in source code but it excepts only one additional routine that handle timing delay. 

Schematic Diagram

Program in MikroC

	#define Ticks_Per_Ms 4
	#define OUTPUT PORTD.RD0
	char counter;
	unsigned ms_count;
	void interrupt() {
	if(INTCON.T0IF) {
	counter++;
	if(counter==Ticks_Per_Ms)
	{ counter=0; ms_count++;}
	}
	INTCON.T0IF=0; // CLEAR INTERRUPT FLAG
	}
	void ms_delay(unsigned count) {
	while(ms_count<count);
	ms_count=0;
	}
	void main() {
	PORTD=0x00; // CLEAR PORTD
	TRISD=0x00; // SET PORTD OUTPUT
	OSCCON|=0x70; // SELECT 8MHz INTRC
	OPTION_REG.T0CS=0; // SELECT INTERNAL SOURCE
	OPTION_REG.PSA=0; // PRESCALER ASSIGNED TO TIMER0
	OPTION_REG&=0xF8; // SELECT 1:2 PRESCALER
	INTCON.GIE=1; // ENABLE GLOBAL INTERRUPT
	INTCON.T0IE=1; // ENABLE TIMER0 OVERFLOW INTERRUPT
	INTCON.T0IF=0; // CLEAR INTERRUPT FLAG
	counter=0;
	ms_count=0;
	TMR0=0; // CLEAR TIMER0
	while(1) {
	OUTPUT=1;
	ms_delay(100);
	OUTPUT=0;
	ms_delay(50);
	}
	}

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