The FlexRay controller relieves the host of all communication tasks. The FlexRay controller is connected to the host via the so-called CHI (Controller Host Interface). On-board the CHI there are user-configurable buffers for TX and RX messages. Buffers for RX messages are also equipped with acceptance filters. Status and control registers are also housed in the CHI

Representing the core of the FlexRay controller is the protocol engine. It consists of several communication components. The media access control (MAC) component for bus access. The coding component handles coding of the bytes obtained from the MAC. The decoding component handles decoding of the logical bit stream received by the FlexRay transceiver.

The frame and symbol processing (FSP) component checks for conformance to the communication cycle upon which the FlexRay cluster is based and it checks the RX messages for transmission errors. The clock synchronization process component provides for synchronization of the FlexRay nodes. The wake-up and startup component handles wake-up and startup.

A FlexRay controller may enter eight different states depending on the progress of communication. Each controller state is characterized by certain communication-specific activities, in which very specific communication components are active. The communication component protocol operation control (POC) is responsible for controller state transitions.