If you design the bitbanging serial interface to the serial eeprom correctly and then save all registers that are used in the interrupt routine then there should be no reason that would prevent you from accessing the eeprom in the mainline code and get vectored to the ISR (interrupt service routine) every once in a while. I have designed systems that operate in this manner many times. Just use care that the interrupt routine does not change any of the I/O bits that are being used for the handshaking to the serial eeprom. Also do not try to call the serial eeprom routines from the interrupt context. And finally try to keep the processing time in the interrupt routines as small as possible.

When I have followed these considerations I found no need to clear the EA flag for either an I2C driver I coded or for an SPI driver.

Michael Karas