The PCA9549 provides eight bits of high speed TTL-compatible bus switching controlled by the I²C-bus. The low ON-state resistance of the switch allows connections to be made with minimal propagation delay. Any individual A to B channel or combination of channels can be selected via the I²C-bus, determined by the contents of the programmable Control register. When the I²C-bus bit is HIGH (logic 1), the switch is on and data can flow from Port A to Port B, or vice versa. When the I²C-bus bit is LOW (logic 0), the switch is open, creating a high-impedance state between the two ports, which stops the data flow.
An active LOW reset input (RESET) allows the PCA9549 to recover from a situation where the I²C-bus is stuck in a LOW state. Pulling the RESET pin LOW resets the I²C-bus state machine and causes all the bits to be open, as does the internal power-on reset function.
Three address pins allow up to eight devices on the same bus.