BUDE_Manual-CANopen_EN.doc
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Baumer Hübner GmbH
23.10.2012/bja
Berlin, Germany
3.3
CANopen communication
3.3.1
Communication profile
Communication between the network users and the Master (PC / Control) takes place by means of object
directories and objects. The objects are addressed via a 16 bit index. The CANopen communication profile
DS 301 standardizes the various communication objects. They are accordingly divided into several groups:
• Process data objects PDO for real time transmission of process data
• Service data objects SDO for read/write access to the object directory
• Objects for synchronization and error display of CAN users:
SYNC object (synchronization object) for synchronization of network users
EMCY object (emergency object) for error display of a device or its peripherals
• Network management NMT for initialization and network control
• Layer Setting Services LSS for configuration by means of serial numbers, revision numbers etc. in the
middle of an existing network
3.3.2
CANopen message structure
The first part of a message is the COB ID (Identifier).
Structure of the 11-bit COB ID :
Function code
Node ID
4-bit function code
7-bit node ID
The function code provides information on the type of message and priority
The lower the COB ID, the higher the priority of the message
Broadcast messages:
Function code
COB ID
NMT
0h
SYNC
80h
Peer to peer messages:
Function code
COB ID
Emergency
80h + Node ID
PDO1 (tx)
1)
180h + Node ID
PDO2 (tx)
1)
280h + Node ID
SDO (tx)
1)
580h + Node ID
SDO (rx)
1)
600h + Node ID
Heartbeat
700h + Node ID
LSS (tx)
1)
7E4h
LSS (rx)
1)
7E5h
1): (tx) and (rx) from the viewpoint of the encoder
The node ID can be freely selected by means of the CANopen bus between 1 and 127 (if rotary switches =
0). The encoders are supplied with the Node ID 1.
This can be changed with the service data object 2101h or using LSS.
A CAN telegram is made up of the COB ID and up to 8 bytes of data:
COB ID DLC
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
xxx
x
xx
xx
xx
xx
xx
xx
xx
xx
The precise telegram is outlined in more detail at a later point.
