Chapter 13 CANopen Overview
|
C200 Series
13-5
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.
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:
PDO
Type Number
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.
Data 0
Data 1 Data 2 Data 3 Data 4 Data 5 Data 6 Data 7
7 6 5 4 3 2 1 0 Index
Index
Index
Data Data Data
Data
Type
command
L
H
Sub
LL
LH
HL
HH
Client
0
0
1
-
N
E S
Initiate
Domain
Download
Server 0 1 1 -
-
-
-
-
Client
0
1
0
-
-
-
-
-
Initiate
Domain
Upload
Server
0
1
0
-
N
E S
Client
1
0
0
-
-
-
-
-
Abort Domain
Transfer
Server
1
0
0
-
-
-
-
-
N: Bytes not use
E: normal(0)/expedited(1)
S: size indicated
Call 1(800)985-6929 for Sales
deltaacdrives.com
sales@deltaacdrives.com
Call 1(800)985-6929 for Sales
deltaacdrives.com
sales@deltaacdrives.com
