.ORIG	x3000

	LEA	R1,Isr
	STI	R1,Intrpt
	LD  	R6,STACKB    ; initialize stack pointer
	LEA	R1,EBit
	STI	R1,KBSR

InfLoop	AND	R1,R1,#0 ; make sure it's infinitely cleared
	BR	InfLoop

Isr
	AND R0, R0, #0      	; Save R7 (return location)
    	ADD R0, R7, #0
    	JSR PUSH
    	AND R0, R0, #0     	; Save R5 (frame pointer)
    	ADD R0, R5, #0
    	JSR PUSH
    	AND R0, R0, #0     	; Save R1
    	ADD R0, R1, #0
    	JSR PUSH

Monitr	LDI	R1, DSR		;polling monitor
	BRzp	Monitr
	STI	R0,DDR

	JSR POP			; Restore R1
    	ADD R1,R0,#0
    	JSR POP			; Restore R5
    	ADD R5,R0,#0
    	JSR POP			; Restore R7
    	ADD R7,R0,#0

	RTI

;------------------------
PUSH	ADD	R6,R6,#-1
	STR	R0,R6,#0
	RET
;------------------------

;------------------------
POP	LDR	R0,R6,#0
	ADD	R6,R6,#1
	RET
;------------------------

	halt

STACKB	.FILL 	0xFD00 ;stack
Intrpt	.FILL	0x0180 ; interrupt location
EBit	.FILL	0x4000 ;enable bit for kbsr
DSR	.FILL	xFE04 ;display
DDR	.FILL	xFE06 ;display
KBSR	.FILL	xFE00 ;keyboard
KBDR	.FILL	xFE02 ;keyboard

	.end

;Keybrd	LDI	R1,KBSR	;polling keyboard
;	BRZP	Keybrd
;	LDI	R0,KBDR
;	BR	Next1