If the TWI is used in an SMBus environment, the Inactive Bus Time-Out (TIMEOUT) bit field from the Host Control A (TWIn.MCTRLA) register must be configured. It is recommended to write to the Host Baud Rate (TWIn.MBAUD) register before setting the time-out because it is dependent on the baud rate setting.

A frequency of 100 kHz can be used for the SMBus environment. For the Standard mode (Sm) and Fast mode (Fm), the operating frequency has slew rate limited output, while for the Fast mode Plus (Fm+), it has x10 output drive strength.

The TWI also allows for an SMBus compatible SDA hold time configured in the SDA Hold Time (SDAHOLD) bit field from the Control A (TWIn.CTRLA) register.