Define the ports of AT89C51 as input or output.

What is port0, port1, port2, port3? Individual pins or full 8-bit ports?

With most 8051 chips, you don't have to change a setting to use a pin as input or output. It has a weak pull-up, so when you set the pin as high from the inside, any external equipment can use it as an input. If you set the pin as low from your program, it will be able to sink current.

Just note that the reset state is the weak pull-up state, and it really is weak and not intended to supply power to a LED or similar.

Have you spent time reading up on the 8051 in general, and your specific chip?

What is port0, port1, port2, port3? Individual pins or full 8-bit ports?

With most 8051 chips, you don't have to change a setting to use a pin as input or output. It has a weak pull-up, so when you set the pin as high from the inside, any external equipment can use it as an input. If you set the pin as low from your program, it will be able to sink current.

Just note that the reset state is the weak pull-up state, and it really is weak and not intended to supply power to a LED or similar.

Have you spent time reading up on the 8051 in general, and your specific chip?

See: www.8052.com/.../120176

And: www.8052.com/.../120112

Thanks to support me, ports0-3 are full 8-bit ports.

I m sending my source code please inform me any types of errors

I shell be very thankful to you.

org 00h

;Set up Timer 1
        MOV     IE, #0                  ; Disable all interrupt
        MOV     TMOD, #020h             ; Timer 1: Mode 2 (8-bit reload)
        MOV     TH1, #230d              ; Reload value for 1201, SMOD = 0
        MOV     TL1, #230d              ; Make first time-out correct
        ANL     PCON, #07fh             ; To make SMOD =0

;Set up serial ports
        MOV     SCON, #50h              ; Timer 1 : Mode 1 (vari baud) and set receive enable
        SETB    TR1                             ; Start timer 1
        mov r1, #6d
        mov r2, #91d
        mov r3, #63d
        mov r4, #63d

MainLoop:
setb p0.7

mov r7, #90d
        SubLoop:
        mov r6, #90d
                InnerSpot:
                        jmp DisplayData
                InnerSpot1:
                djnz r6, InnerSpot
        djnz r7, SubLoop

clr p0.7

mov r7, #90d
        SubLoop1:
        mov r6, #90d
                InnerSpot12:
                        jmp DisplayData
                InnerSpot11:
                djnz r6, InnerSpot12
        djnz r7, SubLoop1


jmp MainLoop

DisplayData:
mov C, p2.7
orl C, p0.7


        mov b, r1
   mov p2, b
JNC Skip1
        mov b, #254d
        mov p1, b
Skip1:
                mov b, #255d
           mov p1, b
        mov b, r2
   mov p2, b
JNC Skip2
        mov b, #253d
   mov p1, b
Skip2:
                mov b, #255d
           mov p1, b

        mov b, r3
   mov p2, b
JNC Skip3
        mov b, #251d
   mov p1, b
Skip3:
                mov b, #255d
           mov p1, b

        mov b, r4
   mov p2, b
JNC Skip4
        mov b, #247d
   mov p1, b
Skip4:
                mov b, #255d
           mov p1, b

        jnb RI, CheckReturnPoint
        clr RI
        mov a, sbuf

cjne a, #246d, CountCountinus
        mov r0, #0d

CheckReturnPoint:
mov c, p0.7
        jc InnerSpot1
jnc InnerSpot11

CountCountinus:
inc r0

DigOne:
cjne r0, #1d, DigTwo
   mov r1, a
   Jmp DisplayData

DigTwo:
cjne r0, #2d, DigThree
   mov r2, a
   Jmp DisplayData

DigThree:
cjne r0, #3d, DigFour
   mov r3, a
   Jmp DisplayData

DigFour:
cjne r0, #4d, CheckReturnPoint
        mov r0, #0d
   mov r4, a
Jmp DisplayData

End

thanks

very important help

i m really thankful to you

from tyhe above
;Set up serial ports

        MOV     SCON, #50h              ; Timer 1 : Mode 1 (vari baud) and set receive enable
        SETB    TR1                             ; Start timer 1
        mov r1, #6d
        mov r2, #91d
        mov r3, #63d
        mov r4, #63d
MainLoop: