Differences between I2C and SMBus)

SMBus is a two-wire serial bus. Its first specification was commercially available in 1996. It is mostly based on I2C bus specifications. Like I2C, SMBus does not require additional pins. It is created to add new features, but only works at kHz and is dedicated to smart battery management applications. It works in Master/Slave Mode: the master device provides a clock, provides a start bit when it initiates a transmission, and provides a stop bit when it terminates a transmission; the slave device has a unique 7 or 10-bit slave device address. There are some differences in time series between SMBus and I2C bus. First, SMBus requires a certain amount of data retention time, while I2C bus extends the data retention time from the inside. SMBus has a timeout function, so when the SCL is too low and exceeds 35 ms, the slave device resets ongoing communication. Conversely, I2C uses hardware reset. SMBus has an alarm response address (Ara), so when an interruption occurs from the device, it does not immediately clear the interruption, it is maintained until it receives a Ara containing its address sent by the master device. SMBus only works from 10 kHz to up to 100 kHz. The minimum operating frequency of 10 kHz is determined by the SMBus timeout function.