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RPDO Communication Parameters


The Index area from 1400h to 15FFh in the Object Dictionary is reserved for the RPDO communication parameters. The Index range of 512 (200h) ensures that a maximum of 512 RPDOs can be configured in the Object Dictionary of a single CANOPEN node.

The parameters for the first RPDO (RPDO1) are located at Index 1400h, the parameters for the second at 1401h (RPDO2), for the third at 1402h (RPDO3) and so on.

The parameters for each RPDO are accessible via the Subindex. The table below shows the parameters that are available for every RPDO.

SubindexNameData type
0Number of entriesUNSIGNED8
1COB-IDUNSIGNED32
2Transmission typeUNSIGNED8
3Inhibit TimeUNSIGNED16
4ReservedUNSIGNED8
5Event TimerUNSIGNED16

The Number of Entries for a RPDO can be 5 if the Event Timer is supported. The most popular configuration of RPDOs does not use the Event Timer and therefore the Number of Entries is 2.

The COB ID is the connection object identifier which is the CAN message identifier used for this RPDO. This parameter determines which CAN message is received and interpreted as the RPDO belonging to this set of parameters. The default value depends on the Index of the entry, as shown in the following table.

IndexDefault value
1400hNode ID + 00000200h
1401hNode ID + 00000300h
1402hNode ID + 00000400h
1403hNode ID + 00000500h
1404h – 15FFh80000000h

For more information see COB ID and CAN ID partitioning.

The Transmission Type determines if this RPDO is to be processed immediately upon reception or if a node needs to wait for a synchronization signal (SYNC), before it may process the data received. The following table lists the available transmission types for a Receive PDO:

Transmission TypeDescription
0 – 240The Receive PDO is synchronous. The data in the PDO is processed on reception of the next SYNC Object. The actual value of the transmission type is not relevant.
241 – 253Not used for Receive PDOs
254The transmission type of the Receive PDO is manufacturer specific.
255The Recieve PDO is asynchronous. As soon as the PDO arrives the data is processed by the node.

The Inhibit Time is not used for RPDOs and if implemented should have the value zero.

The Reserved parameter is a legacy value from previous CANOPEN versions and must not be implemented in nodes conforming to the current standard [CiADS302].

The Event Timer may be used to generate an emergency if this RPDO is not received before the event timer expires. Subentry 05h may optionally be implemented. It is an event timer which configures an event to occur after the specified number of milliseconds. A value of zero disables the event timer. The functionality of the event timer with regard to Receive PDOs is not described in the CANOPEN specification, however it may be used for several purposes, including generating an error if the PDO has not been received within a specific time.