logicchecker.c

Application for PIC18 microprocessor used to test logic of another device.

#include <p18f8680.h>
#include <delays.h>

struct Bits_struct // Set up structure to handle different bits used in program
{
	unsigned char	X1:1; // Reserve 1 bit for X1
	unsigned char	X2:1; // Reserve 1 bit for X2
	unsigned char	FlashX1:1;
	unsigned char	FlashX2:1;
	unsigned char	a:1;
	unsigned char	b:1;
	unsigned char	c:1;
	unsigned char	d:1;
};

unsigned char Truth = 0;
struct Bits_struct	Bits;

void high_isr(void);
void low_isr(void);
	
#pragma code interrupt_at_high_vector = 0x08
void interrupt_at_high_vector(void)
{
	_asm
	GOTO high_isr
	_endasm
}
#pragma code 
#pragma interrupt high_isr
void high_isr(void)
{
	INTCONbits.GIE = 0; //Disable all interrupts
	INTCONbits.T0IF = 0; //Clear TMR0 interrupt flag
	TMR0H = 0x0B; // Reset Timer 0
	TMR0L = 0xDB;
	if (Bits.FlashX1 == 1)
		PORTDbits.RD1 = ~PORTDbits.RD1;
	if (Bits.FlashX2 == 1)
		PORTDbits.RD0 = ~PORTDbits.RD0;
	INTCONbits.GIE = 1; //Enable all interrupts
}

void main (void)
{
	INTCON = 0xE0; // Enable global interrupts, enable TMR0 interrupt, clear TMR0 overflow flag
	RCONbits.IPEN = 0; // Disable interrupt priorities
	T0CON = 0x05; // Set Timer 0 as 16 bit, increment on instruction cycle, 64 prescaler
	TMR0H = 0x0B; // Load 3035 (0x0BDB) into TMR0 register
	TMR0L = 0xDB;
	T0CONbits.TMR0ON = 1; // Turn Timer 0 on
	
	TRISD = 0x00;
	TRISB = 0x0F;
	TRISG = 0xFF;
	PORTD = 0xFF;

			
	while (1)
	{
		if (Truth == 0x10) // Reset truth after it reaches 16
			Truth = 0x00;
		
		// Apply the value of Truth to a, b, c, and d bits	
		Bits.a = Truth >> 3;
		Bits.b = (Truth & 0x04) >> 2;
		Bits.c = (Truth & 0x02) >> 1;
		Bits.d = (Truth & 0x01);
		
		// Apply a, b, c, and d bits to PORTA pins
		PORTBbits.RB7 = Bits.a;
		PORTBbits.RB6 = Bits.b;
		PORTBbits.RB5 = Bits.c;
		PORTBbits.RB4 = Bits.d;
		
		// Conditional statements to implement logic:
    	Bits.X1 = ((!Bits.b && !Bits.c) || (Bits.b && Bits.c) || (Bits.a && !Bits.b && Bits.d)) ? 1 : 0;
       	Bits.X2 = ((!Bits.c && Bits.d) || (Bits.c && !Bits.d) || (Bits.a && Bits.b && Bits.c)) ? 1 : 0;
       	       	
       	// Clear the upper four bits of PORTD
       	// and copy inverted value of Truth to upper 4 bits of PORTD
       	PORTD = (PORTD & 0x0F) | ~Truth << 4;
       	
       	Delay10KTCYx(100); // Long delay to allow for propagation delay in logic
       	
       	// Test if X1 is the same as "Black box" X1
       	if (PORTGbits.RG0 == Bits.X1)
       	{
	       	PORTDbits.RD1 = !Bits.X1; // Turn on LED representing X1
	       	Bits.FlashX1 = 0;
	       	PORTDbits.RD3 = 1;
	    }
	    else
	    {		   
		   Bits.FlashX1 = 1; // Flash X1
		}
	    
	    // Test if X2 is the same as "Black box" X2
	    if (PORTGbits.RG2 == Bits.X2)
	    {
		    PORTDbits.RD0 = !Bits.X2; // Turn on LED representing X2
		    Bits.FlashX2 = 0;
		    PORTDbits.RD2 = 1;
		}
		else
		{
			Bits.FlashX2 = 1; // Flash X2
		}
       	
        while (PORTBbits.RB0);  // Wait until RB0 is pushed
        while (!PORTBbits.RB0); // Hold in loop until RB0 is released
       	Truth++;       	
    }
}