The FPC402 is designed to interface with four ports and aggregate the I2C and low-speed control and status signals associated with these ports into a single host-side interface (I2C or SPI). Multiple FPC402s can be combined to support up to 56 total ports, all of which are controlled via the same host-side interface. This greatly reduces the number of signals which route to the host controller, saving valuable I/O resources, board routing space, and bill of materials (BOM) cost.

Functionally, the FPC402 is organized as shown in Section 8.2. Two types of host-side control interfaces are supported (I2C and SPI) for controlling and monitoring the downstream ports. The FPC402 has two special outputs per downstream port (OUT_C and OUT_D) which can be used to drive port status LEDs.