Module Operation
1238
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
FlexRay Module
A coldstart attempt begins with the transmission of a collision avoidance symbol (CAS). Only a coldstart
node that transmitted the CAS, transmits frames in the first four cycles after the CAS. it is then joined
firstly by the other coldstart nodes and afterwards by all other nodes.
A coldstart node has bits SUCC1.TXST and SUCC1.TXSY set to 1. Message buffer 0 holds the key slot
ID which defines the slot number where the startup frame is sent. The startup frame indicator bit is set in
the frame header of the startup frame.
In clusters consisting of three or more nodes, at least three nodes shall be configured to be coldstart
nodes. In clusters consisting of two nodes, both nodes must be coldstart nodes. At least two fault-free
coldstart nodes are necessary for the cluster to startup.
Each startup frame must also be a sync frame; therefore each coldstart node will also be a sync node.
The number of coldstart attempts is configured by SUCC1.CSA(4-0) in the SUC configuration register 1.
A non-coldstart node requires at least two startup frames from distinct nodes for integration. It may start
integration before the coldstart nodes have finished their startup. It will not finish its startup until at least
two coldstart nodes have finished their startup.
Both non-coldstart nodes and coldstart nodes start passive integration through the integration path as
soon as they receive sync frames from which to derive the TDMA schedule information. During integration
the node has to adapt its own clock to the global clock (rate and offset) and has to make its cycle time
consistent with the global schedule observable at the network. Afterwards, these settings are checked for
consistency with all available network nodes. The node can only leave the integration phase and actively
participate in communication when these checks are passed.
26.2.6.7.1 Coldstart Inhibit Mode
In coldstart inhibit mode, the node is prevented from initializing the TDMA communication schedule. If the
CCSV.CSI bit in the communication controller status vector register is set, the node is not allowed to
initialize the cluster communication, that is, entering the coldstart path is prohibited. The node is allowed to
integrate to a running cluster or to transmit startup frames after another coldstart node starts the
initialization of the cluster communication.
The coldstart inhibit bit CCSV.CSI is set whenever the POC enters READY state. The bit has to be
cleared under control of the host by CHI command ALLOW_COLDSTART (SUCC1.CMD(3-0) = 1001).