Hello

Thank for everybody for your help.

I found my problem. There is error in my code!
It is :
Cjne r7,#0FFh, loop

This skip FF value of pointer so that the data send to PC is error.
So must write after that line :
call lookup
call ... (subroutine to send data to PC)

My board now run well. I have to buy a new 89C51, an dit run well. I still don't know, I can write and read from the old 89C51. But the board doesn't work?? It works with the new!!

Many thanks