US Patent 7793022 Repeater for a bidirectional serial bus

A digital bit-level repeater for joining two wired-AND buses such as the I2C bus is described. A protocol detector is used for tracking clock and data signals to determine the direction of the transfer. A state machine reads and regenerates the clock lines of both buses and provides the clock-stretching protocol feature on both buses. The repeater is designed to pass data bits from one bus to the other transparently when possible, and to latch and hold each data bit until the receiving bus can be clocked when clock-stretching occurs or when the bus is turned around.