SDA	BIT		P1.0
CLK	BIT		P1.1
KDKEY	BIT     	P1.2		;定義鍵盤檢測位
FRIT	EQU     	P1              ;定義P1口

DBUF0   DATA		40H             ;顯示緩沖區首址
DBUF1	DATA		41H
DBUF2   DATA		42H
DBUF3   DATA		43H
DBUF4   DATA		44H
BUF     EQU		45H             ;存放中間變量
LENTH   EQU		05H             ;顯示緩沖區長度

	ORG	0000H
	AJMP	MAIN

	ORG	0100H
MAIN:
	MOV	SP,#60H
        MOV	40H,#00H
	MOV	41H,#00H
	MOV	42H,#00H
	MOV	43H,#00H
	MOV	44H,#00H
	MOV	TMOD,#20H	;設置T1為方式2
	MOV	TH1,#0FDH	;設置波特率為9600
	MOV	TL1,#0FDH
        MOV	SCON,#50H	;設置串口位方式1
	MOV	PCON,#00H
	SETB	TR1

UP:
	ACALL	DISPLAY

	JB	RI,URXD
	SETB	KDKEY
	MOV	A,#00H
	ACALL	TXDBYTE
	JB	KDKEY,UP
	ACALL	KEY
UTXD:	
	MOV	A,R1
	MOV	SBUF,A
WAIT:	JBC	TI,UP
	AJMP	WAIT
	AJMP	UP

URXD:	MOV	A,SBUF
RXDRET:
	MOV	40H,A
	MOV	41H,A
	MOV	42H,A
	MOV	43H,A
	MOV	44H,A
	CLR	RI
	AJMP	UP

TXDBYTE:
	PUSH	   PSW
	PUSH	   ACC	
	MOV	   R3,#08H
TXDUP:	RLC	   A
	MOV	   SDA,C
	CLR	   CLK
	SETB	   CLK
	DJNZ	   R3,TXDUP
	POP	   ACC
        POP	   PSW
	RET											

KEY:	
	SETB		KDKEY
	MOV		R1,#00H		;賦初值
	MOV		A,#0FEH		;是，則判斷其鍵值
KEYZHI:	ACALL		TXDBYTE		;是此鍵嗎？
	JNB		KDKEY,KEYRET	;是，則保存退出
	RL		A		;否則檢測下一個鍵
	INC		R1
	CJNE		A,#7FH,KEYZHI	;檢測完了嗎？
KEYRET:	
	MOV		FRIT,#0FFH
	RET

DISPLAY:  
           MOV     R2,       #7FH     ;給位碼初值
           MOV     R0,       #DBUF0   ;給顯示緩沖區首值
ZCQ:       MOV     A,        @R0
           LCALL   TAB                ;查表取段碼
           ACALL   TXDBYTE		      ;送段碼輸出
           MOV     BUF,      FRIT
           ANL     BUF,      #07H
           MOV     A,        R2       ;保證不影響其它位送位碼
           ORL     A,        BUF       
           MOV     FRIT,     A
           LCALL   DELAY              ;調延時子程序
 	   MOV	   FRIT,#0FFH
           INC     R0
           MOV     A,        R2
           RR      A
           MOV     R2,       A
           CJNE    R0,       #45H,  ZCQ;5位顯示完嗎?
           MOV     R0,       #40H
           MOV     R2,       #7FH
	   MOV	   FRIT,     #0FFH
           RET
;延時子程序
DELAY:     MOV     R7,      #50H     ;12M時鐘下延時1MS	
DELAY0:    MOV     R6,      #10H
DELAY1:    DJNZ    R6,      DELAY1
           DJNZ    R7,      DELAY0
           RET
;查表子程序
TAB:       INC     A	             ;基地址加一
           MOVC    A,       @A+PC    ;查段碼表，取其相應的段碼
           RET
DB         0C0H,0F9H,0A4H,0B0H,099H,092H,082H,0F8H,80H,090H,088H,083H,0c6H,0a1H,86H,8eH,0bfH,89H,8CH
	   ;(0-9 A-F)共陽段碼表						
	   END