'
' eBASIC interrupt example
'
' This program illustrates how to code a user interrupt
' handler. In this example, we are capturing the TMR0 
' overflow interrupt. TMR0 is set to overflow every 1 ms 
' in the eBASIC startup code. We captuer the interrupt
' and increment our tick counter to implement a crude
' real-time clock. Meanwhile, we are incrementing a 
' foreground counter and displaying it's results, just for fun.
'
' Note that both the foreground and background routines use the
' 16-bit math operations. The math library is reentrant.
'
' See the PIC 16F877 data sheet for more info
'
' Copyright(c) 2004, Compubotics LLC
' Use freely for non-commercial purposes.
' www.compubotics.com

#include "rc40.inc"
#interrupt intHandler

rtcCounter var	word
forecounter var word

' define some handy bit variables that we need
#bit T0IF,INTCON,2
#bit T0IE,INTCON,5
#bit GIE,INTCON,7

Main:

	' enable timer 0 interrupt
	T0IE = 1
	
	' global interrupt enable 
	GIE = 1
	
	' loop here forever
	while (1)
		' increment the foreground counter
		forecounter = forecounter + 1
		
		' display the counters every 100th tick of the foreground counter
		if (forecounter // 100) = 0 then
			debug dec forecounter,":", DEC rtcCounter, cr
		endif
		
	wend
	

end

' -------------------------
' interrupt handler routine
' -------------------------
intHandler:

	' handle TMR0 interrupt
	if (T0IF) then
		' increment our RTC
		rtcCounter = rtcCounter + 1
		' MUST RESET TMR0 INTERRUPT FLAG!!!
		T0IF = 0
	endif
	
return