P1 port 4 & TImes; 4 keyboard, the output uses a 74LS164 to drive a digital display.
; When a key is pressed, the key is displayed on the digital display.
The program is written in assembly language and the debug screen with PROTEUS is as follows:
The procedure is as follows:
ORG 0000H
LJMP START
ORG 0030H
START:
MOV P1, #255
MOV 60H, #16
MAIN:
CALL DISPLAY
;SJMP $
M_LOOP:
CALL K_SCAN ; Scanner
JB ACC.4, M_LOOP
LJMP MAIN
;---------------------------------------
DISPLAY:
MOV A, 60H
MOV DPTR, #D_TAB ; first address of code table
MOVC A, @A + DPTR
CPL A
MOV R2, #8
INI1:
RRC A
MOV P3.0, C ; A low output to P3.0
CLR P3.1; shift pulse
SETB P3.1
DJNZ R2, INI1 ; 8 shifts
RET
;-------------------------
D_TAB: ; segment code table
DB 03FH, 006H, 05BH, 04FH
DB 066H, 06DH, 07DH, 007H
DB 07FH, 06FH, 077H, 07CH
DB 039H, 05EH, 079H, 071H, 000H
;---------------------------------------
K_SCAN:
MOV P1, #240; all rows are 0
MOV A, P1 ; Read Out Column
CJNE A, #240, COW; There is a key press to transfer
SETB ACC.4; no keymarks
RET
;-------------------------
COW:
MOV P1, #15; each column is 0
ADD A, P1
MOV 60H, A ;Save Key
;-------------------------
MOV DPTR, #KEY_TAB ;Key Code Table First Address
MOV R2, #0; starting from the 0th
K_S1:
MOV A, R2
INC R2
MOVC A, @A + DPTR
CJNE A, 60H, K_S1 ; if compared with 60H content, continue to check
DEC R2
CJNE R2, #16, K_ED
SETB ACC.4; no keymarks
RET
;-------------------------
K_ED: ;There is a key press
MOV 60H, R2 ; Save key number
CALL DELAY ; Eliminating jitter
WAIT:
MOV P1, #0F0H
MOV A, P1
CJNE A, #0F0H, WAIT ; waiting for release
CLR A
RET
;-------------------------
KEY_TAB: ;Keycode table
DB 07EH, 0BEH, 0DEH, 0EEH
DB 07DH, 0BDH, 0DDH, 0EDH
DB 07BH, 0BBH, 0DBH, 0EBH
DB 077H, 0B7H, 0D7H, 0E7H
;---------------------------------------
DELAY: ;Delay
MOV R5, #10
D2: MOV R6, #2
D1: MOV R7, #248
DJNZ R7, $
DJNZ R6, D1
DJNZ R5, D2
RET
;---------------------------------------
END
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