Omron C200HW-CORT21-V1, Operation Manual

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Communication
Section 1-3
11
Max. Data The maximum amount of data that can be transferred per SDO depends on
whether it is an expedited-, block- or segmented transfer.
•
Expedited transfers are limited to 4 bytes
•
Block transfers are limited to 127 segments
•
Segmented transfers are unlimited.
Block transfer is faster than segmented transfer because the transfer is only
acknowledged after the total down- or upload. In the case of segmented
transfer, every client SDO segment must be acknowledged.
1-3-3 Special Function Objects
The following objects are included in the category Special Function Objects:
•
SYNC Object
•
Time Stamp Object
•
EMCY Object
These objects follow the producer / consumer communication model.
1-3-3-1 SYNC Object
Process synchronisation
A SYNC Object enables the synchronisation of processes on the CANopen
network. A SYNC object is transmitted by a SYNC Producer and can be
processed by one or more SYNC Consumers (see figure below).
CANopen devices may be SYNC Producer, SYNC Consumer, neither, or
both. Specific behaviour as producer or consumer is configurable.
SYNC Objects are also configurable, and are characterised by:
•
message identifier
•
communication cycle time
•
window length (see also section 1-3-1-1).
A high priority message identifier is assigned to a SYNC Object to guarantee
an accurate communication cycle time. By default, a SYNC Object does not
contain data.