microcontrller 8051 coding

;***********************************************************************
;receiver code for RLP434A module
;this one works with Holtek decoder 12D
;
$mod51
;port 3 pinouts
LED 		equ	p3.5	;
BUZZ		equ	p3.6	;buzzer
VT		equ	p3.2  ;if high, valid byte rec'd

count1	equ	09h		;
count		equ	08h		;
;----------------------------------------------------
org	00000h
Reset:
	sjmp	Start			; reset vector
Start:
	MOV   SP,#30h          	; Set up stack pointer
	mov	a,#0FFh		; 
	mov	p1,a			;
	mov	p3,a			;
;----------------------------------------------	
Main:	
	mov	p1,#0FFh		;P1 = input
	setb	LED			;LED OFF
	setb	VT			;VT = input

;wait here until VT goes high	
Main1:
	jnb	VT,$			;if VT = high, valid byte rec'd
;----------------------------------------------
	mov	a,P1			;read P1
	xrl	a,#0F0h		;only need low nibble
	CJNE	a,#05h,Main1	;received a "5" ring buzzer
					;else, discard byte and wait for another
;----------------------------------------------
	clr	LED			;LED ON
RX_OK:	
	mov	count1,#5		;ring buzzer 5 times

WaitLp:
	clr	BUZZ			;buzzer on
	lcall	Delay250		;wait 1/4 second
	setb	BUZZ			;buzzer off
	lcall	wait			;wait 1 second

	djnz	count1,WaitLp
;----------------------------------------------
stop:
	sjmp	stop			;wait until hardware reset
;----------------------------------------------	
;1 sec delay @11.0592MHz
wait:	
	mov	count,#4	
wait1:
	lcall	Delay250
	djnz	count,wait1
	ret
;----------------------------------------------	
; 250mS @11.0592MHz
Delay250:
	MOV   R3,#2
      MOV   R2,#194
      MOV   R1,#56
Del250:
	DJNZ  R1,Del250
      DJNZ  R2,Del250
      DJNZ  R3,Del250
      RET
;----------------------------------------------
end