Use the microcontroller AT89C51 to drive the two-digit digital tube to display 00--99 in order to cycle the program code

;The two-digit digital tube displays 00--99 in sequence.

org 0000h

a_bit equ 20h; The single digit of the digital tube stores the memory location

b_bit equ 21h; The tens digit of the digital tube stores the memory location

temp equ 22h ;The counter value is stored in the memory location

star: mov temp,#0; initialize counter, starting from 0

stlop: acall display; call display subroutine

inc temp; add 1 to the counter

mov a,temp

cjne a,#100,next ; Determine whether the counter is full of 100?

mov temp,#0; clear it when it reaches 100 and start again

next: ljmp stlop; loop if not satisfied

;display subroutine

display: mov a,temp ;Convert the hexadecimal number in temp to decimal

mov b,#10 ;decimal/10=decimal

div ab

mov b_bit,a ; the tenth bit is in a

mov a_bit,b ;the ones bit is in b

MOV DPTR,#NUMTAB; specifies the starting address of the table lookup

mov r0,#4

dpl1: mov r1,#250;

dplop: mov a,a_bit; take single digit

MOVC A,@A+DPTR; Check single-digit 7-segment code

mov p0,a ;send 7 pieces of code of units digit

clr p2.7; turn on ones digit display

acall d1ms ;display 162 microseconds

setb p2.7; turn off the units display to prevent ghosting

mov a,b_bit ; take ten digits

MOVC A,@A+DPTR; Check 7 code segments with ten digits

mov p0,a ;send 7 pieces of code with ten digits

clr p2.6; Turn on tens digit display

acall d1ms ;display 162 microseconds

setb p2.6; turn off tens digit display to prevent ghosting

djnz r1,dplop; loop executed 250 times

djnz r0,dpl1; loop execution 250X4=1000 times

ret

;2+2X80=162 microseconds, the delay is calculated according to 12MHZ

D1MS: MOV R7,#80

DJNZ R7,$

RET

;The common cathode display code of the 7-segment digital tube from 0 to 9 on the experimental board

NUMTAB:DB 0CFH,03H,5DH,5BH,93H,0DAH,0DEH,43H,0DFH,0DBH

end