If you meen In System Programing, than:

Have you looked at the datasheet? I think, you can find there every thing you need :)


you can find it there:
http://www.atmel.com/atmel/acrobat/doc0401.pdf

And document about AT89S8252 programing in circute:
http://www.atmel.com/atmel/acrobat/doc0898.pdf

I hope it will help ;)