Parameterization and commissioning
EL6751
114
Version: 3.5
5.4.6
EL6751- SDO communication
CANopen SDO (Service Data Object) communication is used to read or write any parameters in the
CANopen bus node's object directory. The EL6751 CANopen terminal uses the SDO communication for the
configuration of the communication parameters when starting up. Two types of application-specific SDO
communication are additionally possible:
1. Downloading Application-Specific Parameters when Starting Up
The appropriate parameters are to be entered here in the System Manager for the corresponding node in the
"SDO" tab. The objects that result from the configuration in the CAN node tab appear in square brackets.
Any desired number of object directory entries can then be inserted.
Fig. 122: SDO tab, editing an SDO entry
The terminal expects a positive acknowledgement of the parameter download from the relevant bus device.
If it was not possible to write a parameter (the bus device has aborted the SDO) the terminal then attempts
to read the corresponding value back and to compare it with the value that was to be written. This is because
it could, for instance, be a read-only value, and therefore already correctly configured within the bus device.
If the values match the terminal goes to the next parameter entry.
2. Upload and Download at Runtime via ADS
It is possible to perform SDO accesses to the bus devices' object directories using Beckhoff's ADS
communication when the system is running. This is also possible from the PLC, from the NC, from the OPC
server, from ActiveX controls or from any other ADS device.
The whole SDO protocol is handled by the terminal. Using the ADS Write or ADS Read functions the
parameters are transferred to the terminal, and the data is transferred (write) or fetched (read). The
"IDXGRP" parameter here corresponds to the 16-bit index in the CANopen object directory, while
"IDXOFFS" corresponds to the 8 bit sub-index in the CANopen object directory. Details about the ADS
function blocks can be found in the TwinCAT documentation (Beckhoff Information System).
The ADS function block parameters are represented as follows in the SDO parameters:
