9 | More about CANopen?
STÖBER
38
09/2019 | ID 442637.01
9.3.2
Service data object – SDO
node to be configured.
SDOs directly access the entries in the object list of a node and thus help with the parameterization of object directory
entries.
An SDO transmission always consists of at least 2 messages:
A controller usually starts an order with a receive SDO message. Within this order, the controller uses index and subindex to
choose a communication object. The object directory of the drive controller contains a list of all achievable parameters that
are searched and processed in accordance with the sent order. The drive controller then acknowledges with a
corresponding transmit SDO message.
The drive controllers of the 6th generation have 4 independent channels for transmitting service data objects.
The first SDO channel is always enabled. Associated COB-IDs "600 hex + node ID" and "580 hex + node ID" are
unchangeable.
The COB-IDs of the remaining channels can be reselected through corresponding parameterization or the channels can be
disabled. They are disabled by default.
The drive controllers enable the operation of up to 4 axes. For each axis, exactly one SDO channel can be used.
The axes are not addressed by the index and subindex, but by parameter A11 for each SDO channel.
A11.0
A11.1
A11.2
A11.3
A11.4
Device
display
SDO
channel 1
SDO
channel 2
SDO
channel 3
SDO
channel 4
Parameterizing axis 1
Parameterizing axis 2
Parameterizing axis 3
Parameterizing axis 4
Preselection using parameter
A11 for the axis to be edited
In general, SDOs can be used for transmitting data of any length. Here, CANopen distinguishes between 2 SDO transmission
types:
§
Expedited transfer
... for data transmission of up to 4 bytes in a single message.
§
Segmented transfer
... for data transmission of over 4 bytes, which are distributed across multiple messages, i.e. segmented.
