SECTION 2
Accessing The MDrivePlus CANopen
Introduction
The access from the CAN network to the drive is done through data objects.
Process Data Object (PDO)
PDOs are messages in an unconfirmed service. They are used for the transfer of
PDO Attributes
1.Two Types: RPDO (Receive) and TPDO (Transmit)
2.Up to 8 Bytes of application data per message frame. No additional protocol overhead is required.
3.Transfer is not confirmed
4.PDOs Require setup, SDOs map each byte of the PDO to one or more Object Entries.
5.PDOs operate using the Producer (TPDO)/Consumer (RPDO) relationship
6.Best for transferring data such as Device Status,
Producer | Consumer |
TPDO | Data |
RPDO
RPDO
RPDO
Figure 2.1: PDO Producer – Consumer Relationship
Service Data Object (SDO)
A Service Data Object (SDO) reads from entries or writes to entries of the Object Dictionary. The SDO transport protocol al- lows transmitting objects of any size. The first byte of the first segment contains the necessary flow control information includ- ing a toggle bit to overcome the
SDO Attributes
1.Can access any Object in the Object Dictionary regardless of size.
2.Transfer is confirmed
3.Direct access to the Object Dictionary
4.Client/Server relationship.
5.Best for setting up configuration parameters.
Client
ID Request
ID | Request |
Server
Figure 2.2: SDO Client – Server Relationship
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