Hi,
You have to be extra careful though, because in its current version (3.1.2) the Arduino Ameba SDK has a bug in a low-level function called I2C_SlaveWrite() which prevents the I2C slave mode to function properly. This bug was corrected in the AmebaD SDK, but unfortunately still exists in the Arduino SDK.
In order to circumvent this bug I had to reimplement the I2C_SlaveWrite() function in a bug-free private version which now resides permanently in my code.
You can find details about the bug in this discussion, and the corrected version of I2C_SlaveWrite() here.
Good luck!