89C51单片机9个按键的行列式键盘输入电路

若行线为P1.0～P1.2，列线为P1.5～P1.7，试画出只有9个按键的行列式键盘输入电路，并编写按键扫描程序

KEY:MOVP1,#11100000B

MOVA,P1

CPLA

ANLA,#111000000B

JZGORET

KEY1:JBP1.5,KEY2

MOV30H,#00H

KEY2:JBP1.6,KEY3

MOV30H,#01H

KEY3:JBP1.7,GORET

MOV31H,#02H

KEY4:MOVP1,#00000111B

MOVA,P1

CPLA

ANLA,#00000111B

JZGORET

JBP1.0,KEY5

MOVA,30H

KEY5:JBP1.1,KEY6

MOVA,#3

ADDA,30H

KEY6:JBP1.2,GORET

MOVA,#6

ADDA,30H

KEY7:ADDA,#4

MOVDPTR,#TAB

JMP@A+DPTR

TAB:LCALLWORK0

RET

LCALLWORK1

RET

LCALLWORK2

RET

LCALLWORK3

RET

LCALLWORK4

RET

LCALLWORK5

RET

LCALLWORK6

RET

LCALLWORK7

RET

LCALLWORK8

GORET:RET