Hi Mak,

"How to execute the programs from serial eprom?"

This is impossible, but ...

1.
You have parallel SRAM, which can be read as code (using PSEN) and parallel EPROM or Flash programmed with a routine to copy the serial EEPROM into the SRAM and execute from the SRAM.

2.
There is an Atmel application note:
Using the AT89C2051 MCU as Virtual Machine

http://www.atmel.com/atmel/acrobat/doc0592.pdf


Peter