Interfacing RSW-434 TSW-434 With 8051

;*********************************************
;UART Test code
$mod51
;this one uses UART hardware to TX @2400 Baud
;timing is adapted for 11.0592 MHz crystal
;****************************************************
org	00000h
Reset:
	sjmp	Start			;reset vector
Start:
	MOV   SP,#70h           ; Start stack near top of '51 RAM. 
	mov	a,#0FFh		; clear Ports
	mov	p1,a			;
	mov	p3,a			;

;------Initialize Uart------------
	MOV SCON,#01010000B 	;(50H) Mode 1/Rec en
					; bit 4 = REN receive enable				
					; bit 6 = mode 1. -  8 bit uart variable baud rate
;;	MOV TH1,#0E8H 		; Reload value for 1200 Bd @11.0592 MHz
	MOV TH1,#0F4H 		; Reload value for 2400 Bd @11.0592 MHz
;;	MOV TH1,#0FAH 		; Reload value for 4800 Bd @11.0592 MHz
	MOV TMOD,#00100000B	; (21H) Gate1/Timer/Mode 2 / Gate0/Timer/Mode 1
					; bit 5 = 8 bit auto reload for timer 1 (Mode2)
	setb	TR1			; start timer 1	
;----------------------------------------------	
Main:  	
	clr	a
Main1:
	lcall	transmit
	inc	acc
	acall	Time1mS
	sjmp	Main1
;----------------------------------------------	
Time1mS:
	MOV   R2,#2
      MOV   R1,#221
tim1mS:
	DJNZ  R1,$
      DJNZ  R2,tim1mS
      RET
;----------------------------------------------
transmit:
	MOV SBUF,A
	JNB TI,$
	CLR TI
	ret
;----------------------------------------------
end

;*********************************************
;UART Test receiver code
$mod51
;this one uses hardware uart to receive @2400 Baud
;timing is adapted for 11.0592 MHz clock
;
;port 3 pinouts
;----------------------------------------------------
org	00000h
Reset:
	sjmp	Start			; reset vector
Start:
	MOV   SP,#070h          ; Set up stack pointer
	mov	a,#0FFh		; clear Ports
	mov	p1,a			;
	mov	p3,a			;
;------Initialize Uart------------
	MOV SCON,#01010000B 	;(50H) Mode 1/Rec en
					; bit 4 = REN receive enable				
					; bit 6 = mode 1. -  8 bit uart variable baud rate
;;	MOV TH1,#0E8H 		; Reload value for 1200 Bd @11.0592 MHz
	MOV TH1,#0F4H 		; Reload value for 2400 Bd @11.0592 MHz
;;	MOV TH1,#0FAH 		; Reload value for 4800 Bd @11.0592 MHz
	MOV TMOD,#00100000B	; (21H) Gate1/Timer/Mode 2 / Gate0/Timer/Mode 1
					; bit 5 = 8 bit auto reload for timer 1 (Mode2)
	setb	TR1			; start timer 1	
;----------------------------------------------	
Main:
	lcall	receive		;receive data from terminal	
	lcall	transmit		;echo it back to terminal
	sjmp	Main
;----------------------------------------------	
; Receive a character and return in ACC
receive:
	JNB RI,$		;wait here for receive int
	MOV A,SBUF		;get data
	CLR RI		;clear receive int
	ret
;----------------------------------------------
;Transmit a character from ACC
transmit:
	MOV SBUF,A
	JNB TI,$
	CLR TI
	ret
;----------------------------------------------	
end

Main1:
	lcall	receive			;receive data from uart
	cjne	a,#099h,Main1	  ;compare received byte with 99h
						;if its different, restart
	mov	08h,a			;save first byte received

;we are here because first received byte compares to 0x99
	lcall	receive			;get second byte
;-------------
	cjne	a,#088h,Main1		;compare received byte with 88h
        mov	09h,a			;save second byte received

;next the program gets two more bytes (total 4 bytes)
;then xor first three bytes together
;then compare last byte with xor value of 3 first bytes
;not the same? go back to Main1
;this way you are SURE that your receiving code won't pick up garbage bytes.
;I mean it always will, but you must ignore the garbage.