MCS8085 BLINK LED TIMER INTERRUPT VERSION

BLINKLED.ASM

;	MCS8085 BLINK LED
;	TIMER INTERRUPT VERSION
;
PORTA	EQU	00H	;8755 PORTA I/O
DDRA	EQU	02H	;8755 PORTA DIRECTION
CSREG	EQU	0F8H	;8156 COMMAND/STATUS REGISTER
TIMRL	EQU	0FCH	;8156 TIMER L
TIMRH	EQU	0FDH	;8156 TIMER H
;
;	RESET VECTOR
	ORG	0000H
	JMP	MAIN
;
;	RST7.5 VECTOR
	ORG	003CH
	DCR	M	;DECREMENT COUNTER
	JNZ	EXIT	;UNTIL 0, NO OPERATION
	IN	PORTA	;READ 8755 PORTA TO A
	CMA		;COMPLEMENT A
	OUT	PORTA	;WRITE A TO 8755 PORTA
	MVI	A,100
	MOV	M,A	;SET 100 TO COUNTER
EXIT	EI		;ENABLE INTERRUPT
	RET		;RETURN
;
;	MAIN ROUTINE
MAIN:	LXI	SP,000H	;SET STACK POINTER
	MVI	A,0FFH
	OUT	DDRA	;SET 8755 PORTA AS OUTPUT
	OUT	PORTA	;SET 8755 PORTA PINS HIGH
	MVI	A,98H
	OUT	TIMRL
	MVI	A,0FAH
	OUT	TIMRH	;SET 8156 TIMER 15000, PULSE, CONTINUANCE
	MVI	A,0CFH
	OUT	CSREG	;8156 TIMER START
	LXI	H,COUNT	;GET POINTER TO COUNTER
	MVI	A,0BH
	SIM		;RST7.5 ENABLE
	EI		;ENABLE INTERRUPT
;
LOOP:	JMP	LOOP	;PERMANENT LOOP
;
;	RAM
	ORG	0800H
COUNT	DS	01H	;COUNTER
;
	END