gistfile1.asm

	ORG	$1000
START:				; first instruction of program
green_t		EQU	60
yello_t		EQU	5
lights		EQU	$2000
timer		EQU	$2001
n_ymask		EQU	%100010	; EW will be red when NS yellow
n_gmask		EQU	%100001
e_ymask		EQU	%010100	
e_gmask		EQU	%001100
		MOVE.B	#1,D0
green		CMPI.B	#1,D0
		BNE	green_e
green_n		MOVE.B	#n_gmask,lights
		JMP	green_c
green_e		MOVE.B	#e_gmask,lights
green_c		MOVE.B	#green_t,D2
		JSR	wait
		JSR	yellow
		NOT.B	D0
		JMP	green
wait		MOVE.B	D2,timer
waitloop	CMPI.B	#0,timer
		BNE	waitloop
		RTS
yellow		CMPI.B	#1,D0
		BNE	yellow_e
yellow_n	MOVE.B	#n_ymask,lights
		JMP	yellow_c
yellow_e	MOVE.B	#e_ymask,lights
yellow_c	MOVE.B	#yello_t,D2
		JSR	wait
		RTS
	END	START		; last line of source