27.2 Overview

The Two-Wire Interface (TWI) is a bidirectional, two-wire communication interface (bus) with a Serial Data Line (SDA) and a Serial Clock Line (SCL).

The TWI bus connects one or several slave devices to one or several master devices. Any device connected to the bus can act as a master, a slave, or both. The master generates the SCL by using a Baud Rate Generator (BRG) and initiates data transactions by addressing one slave and telling whether it wants to transmit or receive data. The BRG is capable of generating the Standard mode (Sm) and Fast mode (Fm, Fm+) bus frequencies from 100 kHz up to 1 MHz.

The TWI will detect Start and Stop conditions, bus collisions and bus errors. Arbitration lost, errors, collision, and clock hold are also detected and indicated in separate status flags available in both Master and Slave modes.

The TWI supports multi-master bus operation and arbitration. An arbitration scheme handles the case where more than one master tries to transmit data at the same time. The TWI also supports Smart mode, which can auto-trigger operations and thus reduce software complexity. The TWI supports Quick Command mode where the master can address a slave without exchanging data.