Eric,

The OP said that he was using an eeprom. He did not say whether he was on a multi-master bus.

I do not know whether there are other masters, and if I had to wait for a full life-history from the OP it would not be possible to know.

Assuming that he is using the eeprom in a single master environment, he is going to read the eeprom on demand and write back when he chooses. If he receives a power failure during a write, then at least he knows what he was doing at the time.

Perhaps you can suggest a scenario where this is unsafe, compared to setting up an IRQ buffer and state machine. There is an equal risk of power failure, and subsequent recovery.

In practice you are always going to do other things while a read/write takes place. You will be polling for an IRQ state to have completed or polling for each individual TWI operation to complete. Sometimes it is worth keeping code simple.

Have you read the Atmel example code ?

David.