Omron C200HW-CORT21-V1, Руководство по эксплуатации

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Communication
Section 1-3
7
1-2-2-3 Communication Interface
The communication interface describes four different types of communication
objects:
•
Process Data Objects (PDOs)
•
Service Data Objects (SDOs)
•
Special Function Objects
•
Network Management Objects (NMT)
PDOs and SDOs are used to access the entries in the object dictionary;
PDOs are always directly linked to application objects, whereas SDOs can
access any entry in the object dictionary.
Special Function Objects are related to the synchronisation and emergency
messaging of the device.
Network Management Objects are used to configure the device, control the
state of the device, and to supervise the device.
Refer to section 1-3 for more details about the communication objects.
1-3 Communication
Producer / Consumer
Client / Server
Master / Slave
Three communication models are applicable to CANopen:
•
Producer / Consumer model
Each station on the network can receive the messages of any
transmitting station. After receiving the message, it is the task of each
individual node to decide if the message has to be accepted or not. This
model describes the CAN broadcast communication capability.
•
Client / Server model
This model describes peer-to-peer communication. The client transmits a
message; the message will be acknowledged by the server. This model
is used to transfer data which exceeds the maximum data length of one
message. The data to be transmitted is first segmented by the sender,
and segments are transmitted one by one. The acknowledgement by the
receiver can be for each segment or group of segments, or for the total
message.
•
Master / Slave model
The communication is always initiated by the master to which the slave
has to respond. The slave is not allowed to autonomously initiate
communication.
The application of these models is explained in more detail in the following
sections, which describe the CANopen communication and related objects.
1-3-1 Process Data Objects (PDOs)
Purpose of PDO
Non-confirmed
A PDO defines a message frame transmitted or received via the CANopen
network, with the purpose of exchanging real-time data (process data). The
PDOs are directly linked to data objects in the object dictionary, and
therefore no overhead is required to indicate the object. The PDO
communication can be described by the producer/consumer model. Process
data can be transmitted (broadcast) from one device (producer) to an
arbitrary number of other devices (consumers).
PDOs are transmitted in a non-confirmed mode.