4-Digit Seven-Segment Display 0-9 Sequence (1 sec) – Hardware as Q38

Use multiplexed P0 segments + P2 digit select.

ORG 0000H
MOV TMOD,#01H
MAIN: MOV R0,#00H ; digit 0
NEXTDIG: MOV A,R0
       MOV DPTR,#SEG
       MOVC A,@A+DPTR
       MOV P0,A ; segments
       MOV A,R0 ; multiplex? Actually display single digit repeated or multiplex all 4 with same?
       ; For 0-9 counter on all digits, display number as 0000-0009 etc - loop multiplex
       ACALL DELAY_1S_4DIGITS ; time-share
       INC R0
       CJNE R0,#10,NEXTDIG
       SJMP MAIN
SEG: DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH
DELAY_1S: ; via timer outer loop 100×10ms
       MOV R7,#100
L1: MOV TH0,#0D8H
    MOV TL0,#0F0H
    SETB TR0
W: JNB TF0,W
    CLR TR0
    CLR TF0
    DJNZ R7,L1
    RET

Logic: Increment 0-9, look up cathode code, output to multiplexed display, 1 sec delay using Timer0 counts. For 4-digit, drive same code to all digits simultaneously or BCD increment with carry.