Positioning module IMD20, IMD40
CanOpen protocol
SDO
he Service Data Object (SDO) makes it possible to access the object directory of a CanOpen
SDO always uses two CAN objects with different IDs, since this protocol is always
An SDO creates a communications channel between two CanOpen participants. The
ssed is the server of this SDO.
Each CanOpen device should dispose of a default SDO. The identifier of the Can objects related to
this default SDO result from a defined Can address plus the node number (node ID) of the device.
T
device. An
confirmed.
device the object directory of which is acce
0x600 +
Node ID
SDO Client
SDO Server
Object
Dictionary
Data
0x580 +
Node ID
Data
Command
Specifier
Index
low byte
Index
High byte
Sub-index
Data byte
0
Data byte
1
Data byte
2
Data byte
3
Data
Address
Flags
The content of the first byte of an SDO (Command Specifier) controls the communication and defines
e.g., if an object is read or written.
An SDO message always consists of 8 bytes, irrespective of the fact, how many data bytes are really
transferred. The unused data bytes can contain any values and have to be ignored. The number of
data bytes can be given in the Command Specifier; it is, however, also defined by the data type of
the object to be transferred.
Basically, there are two different types of an SDO transfer:
parameters with a length of 1-4 bytes are transferred with an SDO telegram (Expedited Transfer).
case of the IMD20, IMD40 drive module, all parameters can be transferred in the framework of the
name), 1009
h
(hardware
cts given do not have to be used
the normal operation.
•
•
data with a length of more than 4 bytes are transferred in several successive SDO telegrams
(Normal Transfer).
In
“Expedited Transfer”, with the exception of the objects 1008
h
(device
version), 100A
h
(software version) and 2081
h
(trace data). The obje
in
81