Sorry. I have tried to debug for a long time. As a beginner, I do not familiar with assembly. I would like to seek help. The following problem is intended to implement a counter with 2 7-segments LED. One is connected to port 1 while the other one is connected to port 2.
The counting rule is count from 0.00s to 0.99s... but I found that the digits are not operated in what I have expected.
--------- code is attached below ------

ORG 00H
AJMP START
ORG 0BH
AJMP TM0_INT

START:
MOV P1, #01H ; INIT the display
MOV P2, #01H ; INIT the display
MOV SP, #60H
MOV DPTR, #TABLE
MOV R2, #0
SETB EA ; Enable interupt
SETB ET0 ; Enable interupt of Timer0
MOV TMOD, #1 ; mode 1
MOV TH0, #ECH ; aimed for 0.01s counting
MOV TL0, #78H
SETB TR0

TM0_INT:
CLR TR0
MOV TH0, #ECH
MOV TL0, #78H
ACALL UP
ACALL CONV
PUSH ACC
MOV A, 20H ; save tenth digit
MOVC A, @A+DPTR
MOV P1, A
MOV A, 21H ; save oneth digit
MOVC A, @A+DPTR
MOV P2, A
POP ACC
SETB TR0
RETI

; --- count up interupt subroutine ---
UP:
MOV A, R2
ADD A, #1
DA A
MOV R2, A
RETI
; --- converting two digits into two individual digit
; and save into 20H and 21H ---
CONV:
MOV A, R2 ; Extracting tenth digit
ANL A, #F0H
SWAP A
MOV 20H, A ; save tenth digit
MOV A, R2 ; Extracting oneth digit
ANL A, #0FH
MOV 21H, A ; save oneth digit
RETI


TABLE:
DB 01H
DB 4FH
DB 12H
DB 06H
DB 4CH
DB 24H
DB 60H
DB 0FH
DB 00H
DB 0CH

END

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Thank you very much

Sunny