Processor       16F84
		Radix   DEC
		EXPAND


		include         "p16F84.inc"
;Crystal 4Mhz


		
_ResetVector	set	0x00
_IntVector	set	0x04

TXByte   EQU 0x10
Counter  EQU 0x11
RXByte   EQU 0x12
IRQC	 EQU 0x13
L1	 EQU 0X14
L2	 EQU 0X15
Temp	 EQU 0X16
Address	 EQU 0x17
RX1	 EQU 0x18
RX2	 EQU 0x19
Flag	 EQU 0x20
DO	 EQU 4
CLK	 EQU 2
CS	 EQU 1
DIN	 EQU 3
IRQ	 EQU 5
SETDELAY EQU 6
WCONFIGHI EQU b'11000010'
WCONFIGLO EQU b'00101011'
RCONFIGHI EQU b'01000000'
RCONFIGLO EQU b'00000000'
WDATAHI	  EQU b'10000000'
RDATAHI	  EQU 0x00
RDATALO   EQU 0x00
RTSL	  EQU b'10000110'
RTSH	  EQU b'10000100'
PARITY	  EQU 0
PM	  EQU 1
RM	  EQU 2
R	  EQU 7
TEST	  EQU 0
_IntVector	set	0x04

	ORG     0
	goto    Start
;
	
	;ORG     _IntVector
	;goto    Interrupt
;

RESPOND
	
	BCF	PORTA,TEST	;
	BSF	PORTA,TEST	;
	Movwf	Temp		;
	clrw 	
RLOOP	Movlw 	RDATAHI		;
	BSF	PORTA,CS	;
	NOP			;
	BCF	PORTA,CS	;
	Call	Shiftout	;
	MovF	RXByte,0	;
	Movwf	RX1		;
	Movlw	RDATALO		;
	Call	Shiftout	;
	BSF	PORTA,CS	;
	MovF	RXByte,0	;
	Movwf	RX2		;	
	BTFSS	RX1,PARITY	;
	GOTO 	RLOOP		;	
		
	BCF	RX2,0		;
	MOVF	RX2,0		;
	BCF	Address,0	;
	BCF 	STATUS,Z	;

	SUBWF	Address,0	;
	BTFSC	STATUS,Z	;
	Call	Senddata	;
	Return

Senddata	
	Call 	DELAY		;ENABLE DRIVERS	
	BSF PORTA,CS		;
	BCF PORTA,CS		;
	
	Movlw RTSH		;
	call Shiftout		;
	Clrw			;
	Call Shiftout		;
	BSF PORTA,CS		;	
		

	BSF	PORTA,CS	;
	BCF	PORTA,CS	;

	Movlw	WDATAHI		;
	Call	Shiftout	;
	Movlw	'A'		;
	Call	Shiftout	;
	BSF	PORTA,CS	;
	Call 	DELAY		;
	Call 	DELAY		;
	Call 	DELAY		;
	Call 	DELAY		;
	Call 	DELAY	
	BSF	PORTA,CS	;
	BCF	PORTA,CS	;
	Movlw	WDATAHI		;
	Call	Shiftout	;
	Movf	Address,0	;
	Call	Shiftout	;
	BSF	PORTA,CS	;
	Call	DELAY		;
	Call	DELAY		;

	BSF PORTA,CS		;
	BCF PORTA,CS		;
	
	Movlw RTSL		;
	call Shiftout		;
	Clrw			;
	Call Shiftout		;
	BSF PORTA,CS		;	

	Return

DELAY

	MOVLW 100	;
	MOVWF L2	;


LOOP2	MOVLW 255    ;
	MOVWF L1	;

LOOP1
	decfsz L1,F;
	GOTO LOOP1;
	
	decfsz L2,F;
	GOTO LOOP2

	Return


Shortwait

	Movlw 0x31
	Movwf L1;
Inner	Decfsz L1,F
	goto Inner

	Return
	


Shiftout

	MOVWF TXByte    	;


LOOP

	
	
	Movlw	8;
	Movwf  	Counter;
	

SO_LOOP 
	rlf	TXByte,F;
	btfsc 	STATUS,C
	goto 	SO_Set
	bcf	PORTA,DO
	goto	SO_Toggle

SO_Set	
	bsf	PORTA,DO

SO_Toggle
	Bcf 	STATUS,C;
	bcf	PORTA,CLK;
	bsf	PORTA,CLK;
	bcf 	STATUS,C ;
	BTFSC	PORTA,DIN;
	BSF	STATUS,C;
	RLF	RXByte,1;
	bcf	PORTA,CLK
	decfsz  Counter,F;
	goto 	SO_LOOP;
	
	return

Readdata
	Movlw 	RDATAHI;
	Call	Shiftout;
	Movlw	RDATALO	;
	CALL	Shiftout;
	Return		;


Setup

	CLRW			;
	CLRF	PORTA		;
	BSF STATUS, RP0 	; 
	MOVLW b'00001000'	; 
				; 
				
	MOVWF TRISA 		; 
	MOVLW b'11111111'
	MOVWF TRISB

	BCF STATUS,RP0
	Return

Configuart
	BSF	PORTA,CS	;
	NOP			;
	NOP			;
	BCF	PORTA,CS	;
	CLRW			;
	MOVLW	WCONFIGHI	;
	Call 	Shiftout	;Send Configuaration Data 
	MOVLW 	WCONFIGLO	;to UART
	Call 	Shiftout	;
	BSF	PORTA,CS	;

	
	BCF	PORTA,CS
	Movlw	RCONFIGHI	;
	Call	Shiftout	;

	BCF	STATUS,Z	;	
	Movlw	RCONFIGLO	;
	Call	Shiftout	;
	BSF 	PORTA,CS	;
	MOVLW 	WCONFIGLO	;
	SUBWF	RXByte,0	;
	BTFSS	STATUS,Z	;	
	GOTO	Configuart	;

	RETURN	
	
ReadAddress
	BSF	PORTA,TEST	;
	BCF	PORTA,TEST	;
	MOVF PORTB,0		;
	MOVWF Address		;
	Return
	
Disint

	
	BSF STATUS, RP0 	; Select Bank 1	
LOOP4	BCF INTCON,GIE 		;Disable All
				; Interrupts
	BTFSC INTCON,GIE 	;All Interrupts
				; Disabled?
	GOTO LOOP4 		;NO, try again
				; Yes, continue
				; with program
				; flow
	BCF STATUS,RP0
	Return

ToggleRTS
	BSF PORTA,CS
	BCF PORTA,CS
	
	Movlw RTSL
	call Shiftout
	Clrw
	Call Shiftout
	BSF PORTA,CS
	Return

Enint
	BSF PORTA,TEST		;
	NOP			;
	NOP			;
	NOP			;
	NOP			;
	BCF PORTA,TEST		;
	BSF STATUS, RP0 	; Select Bank 1	
	Clrw			;
	Movwf 0x81		;
	movlw  0x90  		; Turn on the Receive Interrupts
 	movwf  INTCON
	BCF STATUS,RP0
	Return
Start
	Call Disint
	Call Setup		;Set up Ports
	Call Configuart		;Configure the UART to IRQ Enabled on recieved data
	;Call Enint		;& parity mask
	Call ToggleRTS		;

Loop	Call ReadAddress	;

	btfss PORTB,0		;
	Call RESPOND		;
	goto Loop		;


	End