Ayman,

1) If you are not using the extra timer and extra RAM of 8052, then the simulator is OK (which you said is for 8051).

2) Many problems are not seen on simulators but they occur in real time. If you have an in-circuit emulator, you can debug your code very easily.

Does this occur always at the same area of the code? ( I mean when the CPU reaches that particular location) or it is intermittent?

Please explain some about your software, and which resources you have used in the code.

IA