hi,

AT89S8252 should react to MOVX instruction to read external eprom read and switch it to internal EEprom instead. Seems to be it dosn't happend

You have add a piece of code to enable internal EEPROM access. Look at EEMEN bit of WMCON register. If the bit in not set (what happens after reset by default) then MOVX accesses to external data memory. So set this bit at setup time or better set/clear it before/after the each EEPROM access. In last case EEPROM will be better protected from accidental erasure/modification.

By the way, with some modification of program you may use more cheaper derivative AT89S52 which has no internal EEPROM. In this case you should link 2kb data array with program code as constant data and then access to it with MOVC.

Regards,
Oleg