// IntrptEx.c
//
// Motorola 68HC12 IRQ Interrupt Example Program
// RPK
// January 13, 1999
//
// This program uses the IRQ to interrupt the main routine.
// The IRQ pin - PE1 (# 44 on J8) will generate an interrupt
// when it is pulled low (grounded). Each time it makes a
// high to low transition, the interrupt service routine
// IRQInt() is called and a message is printed. If PE1 is
// held low, the routine will not be called again until the
// pin goes high and is then pull low.
//
// This code was written and tested using Introl C 4.0.

// #includes

#include <hc812a4.h>
#include <introl.h>
#include <dbug12.h>

// interrupt service routine declaration
__mod2__ void IRQInt();

void __main ()
{
	int choice;
	long i;
	
// The IRQ is used to interrupt this module
// Set up interrupt vectors
	DB12->SetUserVector(IRQ, IRQInt);
	
	DB12->printf("Use the EVB RESET button to exit. \n\n\r");
	_H12INTCR=0xC0;		// IRQ falling edge triggered	
	
	choice=0;
	while(1)
	{
// The strange overlap (overwriting the first output of choice seems to be necessary
// to get around a bug in printf. The first parameter value is always wrong!
		DB12->printf("%i\rWaiting for an IRQ interrupt. %i \n\r",choice,choice);
		DB12->printf("\n\r");
	
		choice=choice+1;
		for (i=0;i<65536;i++)	// waste some time
		{
			;
		}
	
	}
}



// IRQ interrupt routine
// NOTE: this is an example of what NOT to do in an interrupt handler. No I/O should
//   be done in interrupt handlers since they are slow and the handler must be quick
__mod2__ void IRQInt()
{
	DB12->printf("   *** IRQI triggered ***\n\r"); // display message when triggered
}