;----------------------------------------------------------------
; LD261.ASM  This program generates the stepper sequence. It 
; will be used to demonstrate the operation of Trap and 
; softare interrupts. You must append the Monitor.asm file and 
; insert the appropriate initializations as you had done in
; an earlier experiment. C.P. Diduch, November 16, 2004.
;----------------------------------------------------------------
; MAIN PROGRAM			; void main(void) {
				;
.EQU	Tmp	R0		; #define Tmp R0
.EQU	M	R1		; #define M   R1
.EQU	S	R2		; #define S   R2
.EQU	Old	R3		; #define Old R3
.EQU	New	R4		; #define New R4
				;
	.ORG	0x8000		; main {
				;
	ADD	S, NULL, NULL	; S = 0;
	ADDL	M, NULL, 1	; M = 1;
	LOADP	Tmp, 0		; Old = 0x0001 & inport(0);
	ANDL	Old, Old, 1	;
M0:				; do {
	LOADP	Tmp, 0		;    New = 0x0001 & inport(0);
        ANDL	New, Tmp, 1	;    
        SUB	NULL, Old, New	;    if (Old != New) {    
	JMPZ	M1		;
	XORL	M, M, 0x0011	;       M = M ^ 0x0011;
	ADD	Old, NULL, New	;       Old = New;
				;       }
M1:	XORL	M, M, 0x0011	;    M = M ^ 0x0011;
	XOR	S, S, M		;    S = S ^ M;  
	INT	1		;    Software Breakpoint 
	STOREP	2, S		;    outport(Stepper, S);
	JMP	M0		;    } 
;----------------------------------------------------------------