BL20 - Communication in CANopen
D301087 0308 - BL20 CANopen4-22
Transmission of Process Data Objects (PDO)
CANopen provides PDO communication (PDO = Process Data
Object). PDOs are fast real-time process data that are handled as
unconfirmed services without a protocol overhead. PDOs can
contain a maximum of 8 bytes of data. They can be assembled and
configured by the user to suit the specific requirements. In addition,
there are a number of transmission/transfer settings (Transmission
types) for process data.
The following attributes can be set for each PDO through the object
"PDO communication parameter":
Communication Parameter COB-ID
The COB-ID is the CAN identifier that is used for the transmission of
a PDO (object 1400
hex
ff and 1800
hex
ff).
COB-IDs are used to define the priority of the message telegrams.
The lowest COB-ID has the highest priority.
For communication between 2 nodes, the COB-ID of the transmit
PDO must be the same as the COB-ID of the receive PDO.
All other PDOs are inactive. This state can be seen from the invalid
bit (Bit 31) of the COB-ID.
Note
As delivered, each BL20 gateway has from none to eight active
PDOs, with COB-IDs that are taken from the Predefined Master-
Slave Connection Set.
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