Mak,

One further note.

*IF* you place hidden code inside a serial EEPROM, you then MAKE your system vulnerable to 8051 virus. Some diabolical person could power down your board, attach a chip clip over your EEPROM, power it up and replace your hidden routine with their diabolical routine.

Its one way for making your product appear poorly designed and help your diabolical competitor suggest the company replace their stock of your product with theirs.

This is not a common occurance because few systems have the RAM available for executing code. Its not uncommon among some applications to run a CRC over the EEPROM to validate it too.

One area where this is more common is with the use of iButtons. Some company use them to hold setting and options information and its easy for another company to recognize an alien iButton presented and use the opportunity to scramble its data. :)

Maybe I'm just too diabolical to see all this potential. :)))

aka j