CAN-8123/CAN-8223/CAN-8423 user’s manual (Revision 3.00, May/22/2009) ------
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Communication
The communication part provides several communication objects and
appropriate functionalities to transmit CANopen messages via the network
structure. These objects include PDO (Process Data Object), SDO (Service
Data Object), NMT (Network Management Objects), SYNC (Synchronous
Objects)…etc. Each communication object has its relative communication
model and functionality. For example, the communication objects for accessing
the device object dictionary is SDO, using the Client/Server structure as its
communication model (section 3.2). Real-time data or I/O values can be
accessed quickly without any protocol by means of PDO communication
objects. The PDO’s communication model follows the Producer/Consumer
structure. It is also named the Push/Pull model (section 3.3). NMT
communication objects are used for controlling and supervising the state of the
nodes in the CANopen network, and it follows a Master/Slave structure
(section 3.5). No matter which kind of communication object is used, the
transmitted message will comply with the data frame defined in the CAN 2.0A
spec. Generally, it looks like the following figure.
