Tx-wakeup Symbol
Rx-wakeup Pattern
(no collision)
Rx-wakeup Pattern
(collision, worst case)
TXL = 15-60 bit times
TXI = 45-180 bit times
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Module Operation
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SPNU563A–March 2018
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FlexRay Module
26.2.6.6.2 Wake Up Pattern (WUP)
The wake up pattern (WUP) is composed of at least two wakeup symbols (WUS). Wakeup symbol and
wakeup pattern are configured by the PRT configuration registers 1,2.
• Single channel wakeup, wake up symbol may not be sent on both channels at the same time
• Wakeup symbol collision resilient for up to two sending nodes (two overlapping wakeup symbols still
recognizable)
• Wakeup symbol must be configured identical in all nodes of a cluster
• Wakeup symbol transmit low time configured by PRTC2.TXL(5-0)
• Wakeup symbol idle time configured by PRTC2.TXI(7-0), used to listen for activity on the bus
• A wakeup pattern composed of at least two Tx-wakeup symbols needed for wakeup
• Number of repetitions configurable by PRTC1.RWP(5-0) (2 to 63 repetitions)
• Wakeup symbol receive window length configured by PRTC1.RXW(8-0)
• Wakeup symbol receive low time configured by PRTC2.RXL(5-0)
• Wakeup symbol receive idle time configured by PRTC2.RXI(5-0)
Figure 26-14. Timing of Wake Up Pattern
26.2.6.7 STARTUP State
The following description is intended to help configuring startup for the FlexRay module. A detailed
description of the startup procedure can be found in the FlexRay protocol specification v2.1 Rev. A.
Any node entering STARTUP state that has coldstart capability should assure that both channels attached
have been awakened before initiating coldstart.
It cannot be assumed that all nodes and stars need the same amount of time to become completely
awake and to be configured. Since at least two nodes are necessary to start up the cluster
communication, it is advisable to delay any potential startup attempt of the node having instigated the
wakeup by the minimal amount of time it takes another coldstart node to become awake, to be configured
and to enter startup. It may require several hundred milliseconds (depending on the hardware used)
before all nodes and stars are completely awakened and configured.
Startup is performed on all channels synchronously. During startup, a node only transmits startup frames.
Startup frames are both sync frames and null frames during startup.
A fault-tolerant, distributed startup strategy is specified for initial synchronization of all nodes. In general, a
node may enter NORMAL_ACTIVE state by:
• Coldstart path initiating the schedule synchronization (leading coldstart node)
• Coldstart path joining other coldstart nodes (following coldstart node)
• Integration path integrating into an existing communication schedule (all other nodes)
See also Figure 26-15 for more information.
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