Delta VFD11AMS21AFSHA, User Manual

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Chapter 15 CANopen Overview

MS300
(High Speed Model)
15-5
SDO (Service Data Objects)
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 (Process Data Object)
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. All transmission types are listed in the
following table:
Type Number
PDO
Cyclic Acyclic Synchronous Asynchronous RTR only
0
○ ○
1-240
○ ○
241-251 Reserved
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.
EMCY (Emergency Object)
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.