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Grundlagen FlexRay BasicsV 1.1 24
2. Scenario – single Coldstart Node in the cluster
After the Wakeup of a Coldstart node, it enters POC:startup state. As a next step, it
checks weather there is already an active communication on the channels. In that case,
it synchronizes itself to the cycle, and enters POC:normal active state.
If there is no communication, the node starts the Startup procedure by sending a
Collision Avoidance Symbol (CAS). This identifies the node als Leading Coldstart
Node. After that, the node sends 4 Startup Sync Frames (SyF), see Figure 2.20 - (1). If
no other node answers (like in this scenario), the Coldstart Node stops its activity after
a defined number of retries, and waits for another node to take the role of Leading
Coldstart Node.
3. Scenario – two or more Coldstart Node in the cluster
After “racing” for the role of Leading Startup Node, the winning node commences the
Startup Procedure as described in scenario 2. All other Coldstart Nodes are called
Following Coldstart Nodes. These commence scheduling after receiving the first two
Sync Frames (SyF), and start synchronizing in the following cycle. In the fourth cycle,
the Following Coldstart Node start sending Sync Frames on their own, the so called
Coldstart Join (see Figure 2.19 and Figure 2.20 - (2)). All other nodes start scheduling
at the 0 th cycle, followed by the synchronization. After the 7 th cycle, they start
transmitting data (see Figure 2.20 - (3)). As with the 8th cycle, there is a normal
communication on the bus, all nodes are in POC: normal active state.
Figure 2.19 Startup sequence
This behavior can be recorded and verified in CANoe, see Figure 2.20. In this case, two
Coldstart Nodes have ben simulated by the software. The control unit under test joins the
communication as expected.
Bäurle 12.10.2012