利用P0口与行列式键盘接口，编写键盘扫描程序，把按键输入的键码，显示在数码管上
//This is the fourth program of the homework
//The date:2013/3/1           The  author：WQ
                     ORG 0000H
                     SJMP MAIN
MAIN:
      MOV DPTR,#TABLE
      MOV R1,#00H
      SETB P2.6
      MOV P0,#00H
      CLR P2.6
      SETB P2.7
      MOV P0,#0H;
      CLR  P2.7
SCAN:   //检测第一行
    MOV P3,#0FEH;
    MOV A,P3
   ANL A,#0F0H
XHPD0:     CJNE A,#0F0H,OK0 
   CALL JIEDIAN
  SJMP NO1
OK0:         CALL DELAY
  MOV A,P3
  ANL A,#0F0H
  CJNE A,#0F0H,MM0
  SJMP XHPD0
MM0:        CJNE A,#0E0H,MM1
 MOV R1,#01H
  CALL JIEDIAN
MM1:        CJNE A,#0D0H,MM2
  MOV R1,#02H
  CALL JIEDIAN
MM2:        CJNE A,#0B0H,MM3
  MOV R1,#03H
  CALL JIEDIAN
MM3:         CJNE A,#070H,XHPD0
  MOV R1,#04H
  CALL JIEDIAN 
 
      //检测第二行
NO1:        MOV P3,#0FDH;
 MOV A,P3
 ANL A,#0F0H
XHPD1:   CJNE A,#0F0H,OK1
 CALL  JIEDIAN
 SJMP NO2
OK1:        CALL DELAY
                MOV A,P3
 ANL A,#0F0H
                 CJNE A,#0F0H,MM00
 SJMP XHPD1
MM00:     CJNE A,#0E0H,MM10
                MOV R1,#05H
 CALL  JIEDIAN
MM10:      CJNE A,#0D0H,MM20
                 MOV R1,#06H
 CALL JIEDIAN
MM20:      CJNE A,#0B0H,MM30
 MOV R1,#07H
 CALL JIEDIAN
MM30:      CJNE A,#070H,XHPD1
                  MOV R1,#08H 
                  CALL JIEDIAN
                     //检测第三行
NO2:         MOV P3,#0FBH;
  MOV A,P3
  ANL A,#0F0H
XHPD2:   CJNE A,#0F0H,OK2
                CALL JIEDIAN
 SJMP NO3
OK2:     CALL DELAY
              MOV A,P3
              ANL A,#0F0H
              CJNE A,#0F0H,MM01
               SJMP XHPD2
MM01:    CJNE A,#0E0H,MM11
                MOV R1,#09H
                CALL JIEDIAN
MM11:    CJNE A,#0D0H,MM21
               MOV R1,#0AH
               CALL JIEDIAN
MM21:    CJNE A,#0B0H,MM31
               MOV R1,#0BH
              CALL JIEDIAN
MM31:    CJNE A,#070H,XHPD2
              MOV R1,#0CH
              CALL JIEDIAN
   
                 //检测第四行
NO3:        MOV P3,#0F7H;
                 MOV A,P3  
                 ANL A,#0F0H
XHPD3:   CJNE A,#0F0H,OK3
                CALL JIEDIAN
               LJMP SCAN
OK3:      CALL DELAY
               MOV A,P3
              ANL A,#0F0H
               CJNE A,#0F0H,MM40
               SJMP XHPD3
MM40:    CJNE A,#0E0H,MM41
              MOV R1,#0DH
              CALL  JIEDIAN
              CALL DELAY
MM41:    CJNE A,#0D0H,MM42
               MOV R1,#0EH
MM42:    CJNE A,#0B0H,MM43
              MOV R1,#0FH
MM43:    CJNE A,#070H,XHPD3
               MOV R1,#10H
               CALL JIEDIAN  
               LJMP scan
ORG 02f0h
DELAY:   MOV R3,#012H 
DELY1:   MOV R4,#011H
DELY2:   NOP
                DJNZ R4,DELY2
                DJNZ R3,DELY1
                RET     
JIEDIAN:
         MOV  A,R1
         MOVC A,@A+DPTR 
         SETB P2.6 
      MOV  P0,A
      CLR  P2.6
      RET
org 0250h   
TABLE: DB
0H,3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH,77H,7CH,39H,5EH,79
H,71H      
END