LIST P=16F877, R=DEC
	#INCLUDE P16F877.INC
	CBLOCK 0X20
	ENDC
;
	CBLOCK
	 W_BAK, STATUS_BAK		
	 KYBUF
	ENDC
;
	ORG 0
	NOP
	BANKSEL TRISB
	MOVLW 0
	MOVWF TRISB
	MOVWF PORTD
	BANKSEL PORTB
	MOVLW H'FF'
	MOVWF PORTB
;


	ORG 4
PUSH:
	MOVWF W_BAK		
	SWAPF STATUS,W
	CLRF STATUS	
	MOVWF STATUS_BAK	
;
	MOVF RCREG,W
	BCF PIR1,RCIF
;
POP:
	SWAPF 	STATUS_BAK,W	; Restore STATUS
	MOVWF	STATUS
	SWAPF 	W_BAK,F		; Restore WREG w/o
	SWAPF	W_BAK,W		; affecting STATUS
	RETFIE
;---------------------------------------------------------------;
NUM_TO_CHR_TBL:
	ANDLW H'0F'
	ADDWF PCL
	DT "0123456789ABCDEF"	; ASCII of numbers 0~F
;---------------------------------------------------------------;
GOTO MAIN

;
MAIN:
	BANKSEL ADCON1		; ADCON1 is in bank1
	MOVLW B'10001110'	; select right(1) justified (d7)
				; 1 ch(AN0)/0 refs
	MOVWF ADCON1
;
	BANKSEL ADCON0
	MOVLW B'01000001'	; select Fosc/8(01), AN0(000)
	MOVWF ADCON0		; a/d done(0), x(0), a/d ON(1)
;
	CALL DLY2_5mS		; wait for input charge

	BANKSEL SPBRG
	MOVLW	103	; SPBRG value for 9600 BAUD @ 16MHZ
	MOVWF	SPBRG
;
	CLRF	TXSTA               	; clear and setup TXSTA(TX9:0=8bit) 
	BSF	TXSTA,BRGH           	; enable high BAUD RATE
	BSF	TXSTA,TXEN           	; enable serial transmission
;
	BANKSEL RCSTA
	CLRF	RCSTA                	; clear and setup RCSTA(RX:0=8bit) 
	BSF	RCSTA,CREN           	; enable continuous reception
	BSF	RCSTA,SPEN           	; enable serial port
;  
	BANKSEL PIE1			; enable recption interrupt
	BSF PIE1,RCIE
;
	BANKSEL PIR1
	BCF PIR1,RCIF			; clear reception flag
	BSF INTCON,PEIE			; enable peripheral interrupt
	BSF INTCON,GIE			; enable global interrupt
;
;***************************************;
MAIN1:
	BSF ADCON0,GO		; start a/d converting
	CALL NUM_TO_CHR_TBL		; convert key data to ASCII
	MOVWF TXREG			; transmit data now!
	BCF PIR1,TXIF
MAIN2:
	BTFSC ADCON0,GO		; a/d convertion finished?
	GOTO MAIN2		; no	
;
	BANKSEL ADRESL		; select bank1
	MOVF ADRESL,W		; read a/d result ( low byte )
;

	GOTO MAIN1
;===============================================================;
;
	#INCLUDE <DLY2_5mS.INC>	  ; 

;
;
	END