;-----------------------------------------------------------------
; EX82.ASM  Responding to the DECE External Interrupt ExtInt.
;          
; C.P. Diduch, 2001
;
; This program assumes responds to the external interrupt, ExtInt
; of the DECE-I microcomputer. Each interrupt request branches
; control to an interrupt handler where LED's connected to
; port-3 are toggled.
;
;    Author(s):
; Signature(s):                              Date:
;-----------------------------------------------------------------
; MAIN PROGRAM			 ; void main(void) {
				 ;
	.ORG	0x8000		 ; "assign the following to ROM"
				 ;
	ADD	R1, NULL, NULL	 ; R1 = 0 ;
        ADDL    R0, NULL, IH  	 ; "initialize interrupt vector"
        STOREM  0, R0            ;
        ADDL    R0, NULL, 0x00F8 ; "write Interrupt Controller
	STOREP	0x001A, R0	 ;  Control Word to clear all
				 ;  Irq's and unmask ExtInt"
	ORL#	FL, FL, 0x0040	 ; "set DECE IF"
                                 ; do {
M0:     JMP     M0               ; }

;-----------------------------------------------------------------
; void interrupt IH(void)
;
; Each time the interrupt handler, IH, is invoked it 
; toggles the state of LED-15 and LED-0 at output port-3.
;
IH:                              ; void interrupt IH(void) {
				 ;
	XORL	R1, R1, 0x8001	 ;    R1 = R1 ^ 0x8001;
        STOREP  0x0003, R1       ;    outport(3, R2) ; 
				 ; 
        ADDL    R0, NULL, 0x0088 ; "write Interrupt Controller
	STOREP	0x001A, R0	 ;  Control Word to clear 
				 ;  IrqExt at Interrupt Controller
				 ;  with IrqExt unmasked"
        RETI                     ; }
;-----------------------------------------------------------------