Reading matrix keyboard based on single chip, using corresponding key value

/*****************************************************
007.ASM

Wiring: P0 port connects to digital tube,
P2 port connects to matrix keyboard
Use timer interrupt, if there is no operation for a period of time, the digital tube will enter the self-circulation display
2010.09.05
**********************************************************/
ORG 0000H
LJMP MAIN
ORG 000BH
LJMP INT_T0
ORG 0020H
MAIN: ; Main program
MOV SP,#50H
MOV DPTR,#LED_DATA ; Get the first address of the table
MOV TMOD,#01H ; Set the working mode of timer T0
MOV TH0,#15H ; Write the initial value of timing
MOV TL0,#9FH
MOV P2,#0FFH ; Assign the initial value of P2 port
MOV R4,#00H ; Assign the initial value of timing count
SETB 00H ; 00H is the key value change flag
SETB TR0 ; Start timer T0
MOV IE,#82H ; Open interrupt
LCALL SHOW ;Digital tube initialization
loop: ;Main loop
LCALL KEY_READ ;Read keyboard
JBC 00H, LOOP0 ;Judge whether any key is pressed, if yes, refresh output and clear timing count
CJNE R4, #0C8H, LOOP ;If no key is pressed, judge whether the timing time is reached, if yes, enter digital tube loop output
LCALL SHOW1 ;If not, return to the main loop and rescan keyboard
SJMP LOOP
LOOP0:
LCALL SHOW
MOV R4, #00H
SJMP LOOP ;Output refresh completed, return to the main loop and rescan keyboard

/*键盘扫描程序*/
KEY_READ:
CLR P2.6    ;P2.6输出低
JB P2.0,N0_0
MOV R0,#01H
LCALL DELAY
JB P2.0,N0_0
JNB P2.0,$
MOV R5,#04H
SETB 00H
SETB P2.6
LJMP NEAT
N0_0:
JB P2.1,N0_1
MOV R0,#01H
LCALL DELAY
JB P2.1,N0_1
MOV R5,#03H
JNB P2.1,$
SETB 00H
SETB P2.6
LJMP NEAT
N0_1:
JB P2.2,N0_2
MOV R0,#01H
LCALL DELAY
JB P2.2,N0_2
JNB P2.2,$
MOV R5,#02H
SETB 00H
SETB P2.6
LJMP NEAT
N0_2:
JB P2.3,N1_0
MOV R0,#01H
LCALL DELAY
JB P2.3,N1_0
JNB P2.3,$
MOV R5,#01H
SETB 00H
SETB P2.6
LJMP NEAT
N1_0:
SETB P2.6
CLR P2.5
JB P2.0,N1_1
MOV R0,#01H
LCALL DELAY
JB P2.0,N1_1
JNB P2.0,$
MOV R5,#08H
SETB 00H
SETB P2.5
LJMP NEAT
N1_1:
JB P2.1,N1_2
MOV R0,#01H
LCALL DELAY
JB P2.1,N1_2
JNB P2.1,$
MOV R5,#07H
SETB 00H
SETB P2.5
LJMP NEAT
N1_2:
JB P2.2,N1_3
MOV R0,#01H
LCALL DELAY
JB P2.2,N1_3
JNB P2.2,$
MOV R5,#06H
SETB 00H
SETB P2.5
LJMP NEAT
N1_3:
JB P2.3,N2_0
MOV R0,#01H
LCALL DELAY
JB P2.3,N2_0
JNB P2.3,$
MOV R5,#05H
SETB 00H
SETB P2.5
LJMP NEAT
N2_0:
SETB P2.5
CLR P2.4
JB P2.0,N2_1
MOV R0,#01H
LCALL DELAY
JB P2.0,N2_1
JNB P2.0,$
MOV R5,#0CH
SETB 00H
SETB P2.4
LJMP NEAT
N2_1:
JB P2.1,N2_2
MOV R0,#01H
LCALL DELAY
JB P2.1,N2_2
JNB P2.1,$
MOV R5,#0BH
SETB 00H
SETB P2.4
LJMP NEAT
N2_2:
JB P2.2,N2_3
MOV R0,#01H
LCALL DELAY
JB P2.2,N2_3
JNB P2.2,$
MOV R5,#0AH
SETB 00H
SETB P2.4
LJMP NEAT
N2_3:
JB P2.3,NEAT
MOV R0,#01H
LCALL DELAY
JB P2.3,NEAT
JNB P2.3,$
MOV R5,#09H
SETB 00H
SETB P2.4
LJMP NEAT
NEAT:
SETB P2.4
RET

/*Display subroutine*/
SHOW:
MOV A,R5
MOVC A,@A+DPTR
MOV P0,A
RET

/*Loop display subroutine*/

SHOW1:      ;
MOV R3,#00H
LOOP1:
MOV A,R3
MOVC A,@A+DPTR
MOV P0,A
MOV R0,#35H
LCALL DELAY
INC R3
LCALL KEY_READ
JB 00H,RETUN1
CJNE R3,#10H,LOOP1
MOV R3,#00H
SJMP LOOP1
RETUN1:
RET

/*Delay subroutine*/

DELAY:
D0: MOV R2,#0FH
D1: MOV R1,#0BFH
D2: DJNZ R1,D2
DJNZ R2,D1
DJNZ R0,D0
RET

/*Timer interrupt T0 processing subroutine*/

INT_T0:
CLR EA
PUSH ACC
INC R4
MOV TH0,#15H
MOV TL0,#9FH
POP ACC
SETB EA
RETI

/*Digital tube display code, 0~F*/

LED_DATA:
DB 03H,9FH,25H,0DH,99H,49H,41H,1FH
DB 01H,09H,11H,0C1H,63H,85H,61H,71H

END