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0198441113586, V2.01, 11.2008
IL•1F CANopen DS301 3 Basics
Fieldbus interface 31
3.4 Process data communication
3.4.1 Overview
This chapter describes the flow of information from the
perspective of your product in compliance with CiA
standard DS301. The designation "receive" relates to a
flow of data from the master to the product, while "transmit"
represents a flow of data from the product to the master.
Process data objects (PDO: Process Data Object) are used for real-time
data exchange of process data such as actual and reference or operat-
ing state of the device. Transmission is very fast because the data is sent
without additional administration data and a response from the recipient
is not required.
The flexible data length of a PDO message also increases the data
throughput. A PDO message can transmit up to 8 bytes of data. If only
2 bytes are assigned, only 2 data bytes are sent.
The length of a PDO message and the assignment of the data fields are
specified by PDO mapping. For more information see chapter 3.4.2.1
"Dynamic and static PDO mapping".
PDO messages can be exchanged between devices that generate or
process process data.
One PDO each is available for sending and receiving a PDO message:
• T_PDO to transmit the PDO message (T: "Transmit"),
• R_PDO to receive data (R: "Receive").