An app note on Microchip dedicated slave devices in I2C systems (PDF!):
Microchip supplies dedicated slave devices that include a two-wire serial interface that is System Management Bus (SMBus) and I2C™ compatible. The SMBus specification is based on the I2C serial communications protocol, but with some differences.
This document describes the key differences that may affect successful application of Microchip two-wire serial interface dedicated slave devices in systems that are designed with an I2C master interface.
This application note assumes that the reader is familiar with reading and writing registers in I2C or SMBus slave devices and has access to the following documents:
• The I2C-bus and how to use it, Philips
Semiconductors document #98-8080-575-01.
• The System Management Bus Specification
Version 2.0. Appendix B provides details of the
major differences between SMBus and I2C.