FlexRay Wakeup and Startup – Part 1

In this series of articles of “FlexRay Wakeup and Startup”, we will discuss about the Wakeup and the Startup procedure of the FlexRay cluster. Starting with it first we will discuss a typical node in a FlexRay cluster.

A FlexRay cluster is a communication system of multiple nodes connected via at least one communication channel.

A node consists of one communication controller which is an electronic component in a node that is responsible for implementing the protocol of the FlexRay communications system, one host that is the part of a node where the application software is executed and up to two bus drivers which is represented by electronic components consisting of a transmitter and a receiver that connect a communication controller to one communication channel.

Typical FlexRay Node
Typical FlexRay Node

The host and the communication controller exchange data through the interfaces. The host provides configuration and control information to the communication controller, and also the payload data that is to be transmitted during the communication cycle. The communication controller provides the status information to the host and delivers the data received from communication frames.


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The interface between the bus driver and the communication controller typically consists of three digital signals.Two are outputs from the communication controller that are used as “transmit data”, “transmit data enable not” and one is an output from the bus driver “receive data”.

The communication controller uses the “transmit data” signal to transfer the actual signal to the bus driver for transmission onto the communication channel. “transmit data enable not” indicates that the communication controller wants the bus driver to send the data from the “transmit data” line to the required channel. The bus driver uses the “receive data” signal to transfer the received signal to the communication controller.

The interface between the bus driver and the host allows the host to control the operating modes of the bus driver and to read error conditions and status information from the bus driver. The minimum thing required for a cluster wakeup is that the receivers of all bus drivers are supplied with power. A bus driver has the ability to wake up the other components when it receives either a wakeup pattern on its channel or external wakeup event.

In the next article we will continue our discussion on the FlexRay Wakeup and Startup procedure.

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