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CANopen Basics - Emergency Message

Emergency Message

As CANopen is not a hierarchical master-slave system, and node monitoring only conveys the communication state and not the actual node status, every node requires a high priority CAN identifier to indicate error situations. This mechanism is referred to as "Emergency Messaging" and the associated communication object "Emergency Message". Such an emergency message consists of eight data bytes in the following form:
 
Error code Error register Vendor specific error field

 
The error codes are specified in DS-301. The high byte distinguishes the error categories:
 
Error code (hex)Error description
00xxError Reset / No Error
10xxGeneric Error
2xxxCurrent
3xxxVoltage
4xxxTemperature
50xxDevice Hardware
6xxxDevice Software
70xxAdditional Modules
8xxxMonitoring
90xxExternal Error
F0xxAdditional Functions
FFxxDevice Specific

 
Simultaneously with transmission of the emergency message, the device writes the error code to [1003], where the error history is stored. The error register is content of the OD entry [1001] with bit-wise coding of the error cause:
 
BitError cause
0Generic Error
1Current
2Voltage
3Temperature
4Communication Error
5Device Profile Specific
6Reserved (always 0)
7Manufacturer Specific

 
The CAN identifier of the emergency message is stored in the device object dictionary under [1014], but this OD entry is optional, as is the emergency event itself.