Hi Hendrya,

I add program in the last address i.e:

ORG 1FF0H
MOV SP,#07H
LJMP 0000H

My question:
Is my program correct?



Unfortunately no. Just because you write a code at 0x1ff0, how do you expect the MCU to enter that point exactly - particularly after the "code fetch mechanism " has gone out of control ? No, this does not work. I have seen some people fill up the unused code memory with 0x00 - the code for NOP. While this may be a good discipline to follow, it does not help in any way to recover a crash.

I already designing the AT89C52 system, but not resist with voltage transient, RFI, induction from motor and etc.

How do you expect that it will resist electrical noise? Focus ALL your attention in elimnating the offending noise. That, like arresting a leak in the roof is good engineering - placing a container under the leak is bad engineering.

Search this forum with terms like EMI, RFI and motors. There is enough guidelines.

Raghu