Issue 01/05 Data transfer using CANopen
CANopen Option Module Operating Instructions
6SE6400-5BC00-0BP0
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3.2.5 PDO (Process Data Object) services
PDO services are used to transfer data which are critical from a time perspective.
PDO connections follow the Producer/Consumer model. Whereby a normal PDO
connection follows the Push model and an RTR connection, the Pull model.
Several objects are mapped in a PDO. This mapping is an agreement between the
sender and receiver as to which object is located at which position in the PDO. This
means that the sender knows at which position in the PDO it should write data and
the receiver knows to where it should transfer data which it received. A more
detailed description of the PDO mapping is provided in Sections 2.2 and 5.4.
Properties and features of PDOs
• Generally unconfirmed data transfer (only confirmed for RTR queries)
• For fast data transfer of up to 8 bytes of net data without protocol overhead
• Data transfer types: Cyclic, synchronously, non-cyclically, synchronously, RTR
synchronously, RTR non-synchronously, non-synchronously
PDO services
Write PDO service
The Write PDO service is unacknowledged. There is a PDO producer which sends
its PDO to the PDO consumer. There can be 0 or more consumers in the network -
but always only one Producer. This service is used for the normal process data
transfer between MICROMASTER 420/430/440 and one of the other CANopen
nodes (e.g. CANopen master). Regarding Receive PDOs, MICROMASTER is the
consumer and regarding Transmit PDOs, is the Producer.
Request
Process Data
PDO Producer
0
Indication
PDO Consumers
L = 0 ... 8
Write PDO
Fig. 3-11 Write PDO service
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