Via system bus (CAN)
Identifier
9
Networking via system bus (CAN)
9.2
9.2.2
l
9.2-2
EDSPM-TXXX-3.0-04/2004
9.2.2 Identifier
The principle of CAN communication is based on a message-oriented data
exchange between a transmitter and many receivers. Therefore, all nodes can
transmit and receive more or less at the same time.
The so-called
identifier
in the CAN telegram, also called
COB-ID
(
Communication
Object Identifier
),controlswhichnodeistoreceiveatransmittedmessage.In
addition to the addressing, the identifier contains information on the priority of the
message and the type of user data.
The identifier consists of a ’basic identifier’ and the node address of the device to
be approached:
Identifier = Basic identifier + node address
z
This node address is set with the coding switch at the module:
– Modular system: At CAN gateway
– Compact system: At each module
z
Network management and sync telegram only require the basic identifier.
z
The identifiers can also be set individually.
(Q 9.4-3)
9.2.3 Saving changes
Note!
z
Changes of the baud rate, node address, identifiers for PDOs,
and the transmission mode for PDOs must be saved with
I2003
h
= 1, for being maintained even after switching off the
supply voltage.
z
Any changes will become effective only after a Reset Node:
– Switch the supply voltage on again
– Execute NMT command ”81
h
” (see chapter ”Network
management (NMT)”)
– Set I2358
h
=1
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