Schneider Electric DS301 manual Communication relationships, Master slave relationships

3 Basics IL•1F CANopen DS301

Example Selection of a COB ID

For a device with the node address 5, the COB ID of the communication object T_PDO1 is:

384+node ID = 384 (180h) + 5 = 389 (185h).

Data frame The data frame of the CANopen message can hold up to 8 bytes of data. In addition to the data frame for SDOs and PDOs, special frame types are specified in the CANopen profile:

•Error data frame

•Remote data frame for requesting a message

The data frames contain the respective communication objects.

3.2.3Communication relationships

CANopen uses 3 relationships for communication between network de- vices:

•Master-slave relationship

•Client-server relationship

•Producer-consumer relationship

Master-slave relationship A network master controls the message traffic. A slave only responds when it is addressed by the master.

The master-slave relationship is used with network management ob- jects for a controlled network start and to monitor the connection of de- vices.

	Slave
Master	Slave
	data
	Slave
	request
Master	Slave
	data

Figure 3.7 Master - slave relationships

Messages can be interchanged with and without confirmation. If the master sends an unconfirmed CAN message, it can be received by a single or by several slaves or by no slave.

To confirm the message, the master requests a message from a specific slave, which then responds with the desired data.

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