Case M4: Arbitration Lost or Bus Error

If the arbitration is lost, the WIF and the Arbitration Lost (ARBLOST) flags in the Host Status (TWIn.MSTATUS) register are set to ‘1’. The SDA is disabled, and the SCL is released. The bus state changes to Busy, and the host is no longer allowed to perform any operation on the bus until the bus state is changed back to Idle.

A bus error will behave similarly to the arbitration lost condition. In this case, the Bus Error (BUSERR) flag in the Host Status (TWIn.MSTATUS) register is set to ‘1’, in addition to the WIF and ARBLOST flags.