8051 Program – timer based led blinking

; timer based led blinking
; 8051 with 12Mhz crystal
; led is connected to P1.0
	ORG 0H
	led EQU P1.0
	delay EQU 30h	;ram location
	time EQU 20	;20 x 0.05 = 1 sec
MAIN:
init:
	MOV delay,#time
	MOV TMOD,#01h	;timer 0 mode 1(16 bit mode)
	MOV TH0,#3ch	;0.05 sec
	MOV TL0,#0b8h
	SETB TR0	;Start Timer 0
toggle:
	SETB led	; turn on led
	ACALL WAIT	; wait for a second
	CLR led	; trun off led
	ACALL WAIT	; wait for a second
	SJMP toggle	; repeat
	SJMP MAIN
WAIT:
	JNB TF0,$	;wait for timer to over flow
	CLR TF0	;clear TIMER 0 flag
	CLR TR0	;stop Timer 0
	MOV TH0,#3ch	;0.05 sec, reload timer
	MOV TL0,#0b8h
	SETB TR0	;Start Timer 0
	DJNZ delay,WAIT	;decrement delay by 1 & check if its 0
	MOV delay,#time	;reload delay constant
	RET
	END

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List of topics: 8051

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