Delta C2000 Series User Manual page 462

SDO is used to access the Object Dictionary in every CANopen node by
Client/Server model. One SDO has two COB-ID (request SDO and response SDO) to
upload or download data between two nodes. No data limit for SDOs to transfer data. But it
needs to transfer by segment when data exceeds 4 bytes with an end signal in the last
segment.
The Object Dictionary (OD) is a group of objects in CANopen node. Every node has
an OD in the system, and OD contains all parameters describing the device and its network
behavior. The access path of OD is the index and sub-index, each object has a unique
index in OD, and has sub-index if necessary. The request and response frame structure of
SDO communication is shown as follows:
PDO communication can be described by the producer/consumer model. Each node
of the network will listen to the messages of the transmission node and distinguish if the
message has to be processed or not after receiving the message. PDO can be transmitted
from one device to one another device or to many other devices. Every PDO has two PDO
services: a TxPDO and a RxPDO. PDOs are transmitted in a non-confirmed mode.
PDO Transmission type is defined in the PDO communication parameter index
(1400h for the 1st RxPDO or 1800h for the 1st TxPDO), and all transmission types are
listed in the following table:
Type Number
0
1-240
241-251
252
253
254
255
Type number 1-240 indicates the number of SYNC message between two PDO
transmissions.
Type number 252 indicates the data is updated (but not sent) immediately after receiving
SYNC.
Type number 253 indicates the data is updated immediately after receiving RTR.
Type number 254: Delta CANopen doesn't support this transmission format.
Type number 255 indicates the data is asynchronous transmission.
All PDO transmission data must be mapped to index via Object Dictionary.
When errors occurred inside the hardware, an emergency object will be triggered an
emergency object will only be sent when an error is occurred. As long as there is nothing wrong with
the hardware, there will be no emergency object to be served as a warning of an error message.
Cyclic Acyclic
Chapter 15 CANopen Overview
PDO
Synchronous Asynchronous
Reserved
15-5
RTR only