;-----------------------------------------------------------------
; EX69.ASM  WIDGET COUNTER	C.P. Diduch 2001
;
; Counts the number of widgets, in binary, transported along a
; conveyor belt and displays the count at the 8-LSB's of output
; port 0x0003. A proximity sensor generates '0' (at bit-0 of input
; port 0x0001) when a widget is in view of the sensor and a '1'
; after the widget moves past the sensor and out of its field of
; view.
;
;    Author(s):
; Signature(s):                              Date:
;-----------------------------------------------------------------
.EQU	IPORT	1		; #define IPORT 0
.EQU	OPORT	3		; #define OPORT 2
				;
        .ORG    0x0000          ; "variable assignments in RAM"
COUNT:  .DS     1               ; unsigned COUNT ;
				;
        .ORG    0x8000          ; "assign the following to ROM"
				;
                                ; void main(void) {
				;
	XOR	R0, R0, R0	; COUNT = 0 ;
	STOREM	COUNT, R0	;
                                ;
W0:     LOADM   R0, COUNT       ; do {
	STOREP	OPORT, R0	;    outport(OPORT, COUNT) ;
				;
W1:     LOADP   R0, IPORT       ;    do {Read sensor ; }
        ANDL    NULL, R0, 1     ;    while (Widget NOT detected)
	JMPNZ	W1		;
				;
W2:     LOADP   R0, IPORT       ;    do {Read sensor ; }
        ANDL    NULL, R0, 1     ;    while (Widget IS detected) {}
	JMPZ	W2		;
				;
	LOADM	R0, COUNT	;
        ADDL    R0, R0, 1       ;    COUNT = COUNT + 1 ;
	STOREM	COUNT, R0	;
        JMP     W0              ;    }
                                ; }