AT89s52 Port 0 always HIGH

[chetan_129]

Hi,
I have made an AT89S52 board on zero pcb ( the schematic is shown in the attachment)and burned the below code in controller.
The problem is PORT 0 is always HIGH(0XFF). all the other ports are showing expected result(0XAA). I have tried keeping Pin PSEN both HIGH and LOW but nothing worked.
I have also checked resister pack connections and the resistance between port pins and VCC. it is also correct.
PORT 2 has the same kind of res pack and same connections and its working fine, so what could be wrong with PORT 0?
Any kind of help is appreciated.
Thanks!!!

org 0
mov a,#0xaa
mov P0,a
mov P1,a
mov P2,a
mov P3,a

sjmp $

 

[Harald Kapp]

Probably unrelated to your problem, but: PSEN is an output and should not be tied to VCC.

 

[chetan_129]

Probably unrelated to your problem, but: PSEN is an output and should not be tied to VCC.

Is there any possibility that only PORT 0 is damaged and not the remaining ports ??? if yes, how can i check it.

 

[Harald Kapp]

if yes, how can i check it.

Try another chip.