Hi Ofir,

From previous posts i persume you mean the internal EEPROM of the AT89S8252.
You'll find this information in the ATMEL Datasheet doc0401.pdf - on page 9 (Data Memory - EEPROM and RAM)

Yes, the EEPROM can be programmed from your code: set EEMWE in WMCON, write one byte to EEPROM range (000h-7FFh), check for RDY/BSY# flag in WMCON !!!
clear EEMWE when done with writing.

BTW, the EEPROM wouldn't make sense if it couldn't be modified from the code.
If you set the lockbits, the EEPROM is also protected from programmer readout, but can be still read/write accessed from the micro.

Cheers, Roger