;******************************************************************************
;int_demo_18
;This program demonstrates setting of high and low priority interrupts,  
;and context saving.  
;External Interrupt 1 is set as high priority, Port B change is set as low.
;Intended for simulation only.
;TJW 14.2.09					Tested by simulation 23.2.09
;******************************************************************************

	#include P18F2420.inc
; 
	org 	00
	goto 	init
;high priority interrupt vector
	org 	08
	goto 	hi_pr
;low priority interrupt vector
	org 	18
	goto 	lo_pr
;
;Initialise interrupts
init bcf 	intcon2,rbip   	;set port B change to low priority
	movlw	B'01001000' 	;enable Int 1, hi priority
	movwf	intcon3
	bsf 	rcon,ipen	;enable interrupt priority
	movlw	B'11001000' 	;set Global enable high and low, and port B change
	movwf	intcon
;Main loop
loop 	movlw 	55		;store a test value in W reg
	nop
	nop
	goto 	loop
;High priority ISR
hi_pr 	movlw 	11  		;change value in W reg
	bcf 	intcon3,int1if
	retfie 	1
;Low priority ISR
lo_pr 	movlw 	33  		;change value in W reg
	movf 	portb,1		;a dummy read must be made to Port B before the flag is cleared
	bcf 	intcon,rbif
	retfie
	end