34.6.3.1 SMBus

The I²C includes three hardware SCL low time-outs which allow a time-out to occur for SMBus SCL low time-out, Host extend time-out, and Client extend time-out. This allows for SMBus functionality These time-outs are driven by the GCLK_SERCOM_SLOW clock. The GCLK_SERCOM_SLOW clock is used to accurately time the time-out and must be configured to use a 32.768 kHz oscillator. The I²C interface also allows for a SMBus compatible SDA hold time.

• T_TIMEOUT: SCL low time of 25..35ms – Measured for a single SCL low period. It is enabled by CTRLA.LOWTOUTEN.
• T_LOW:SEXT: Cumulative clock low extend time of 25 ms – Measured as the cumulative SCL low extend time by a Client device in a single message from the initial START to the STOP. It is enabled by CTRLA.SEXTTOEN.
• T_LOW:MEXT: Cumulative clock low extend time of 10 ms – Measured as the cumulative SCL low extend time by the Host device within a single byte from START-to-ACK, ACK-to-ACK, or ACK-to-STOP. It is enabled by CTRLA.MEXTTOEN.