Do you verify the chip after programming ? can you read back the code you written of the chip ? if you can ,check your code and readed code yourself .

I have tried much of ISP programmers that do the programing AT89Sxx Series, must of them support S53 & S8252 without problems , but none of them worked for me When i tried S51 & S52 ,the programming algorithm differs for these two chips , i am currently using the ASIM khan's ISP programmer and it is working with S51 & S52 chips. here is the link :

http://www.kmitl.ac.th/~kswichit...gm3v0.html

Farshid J.H.