A 4.3.6 Canopen Over Ethercat; A 4.3.7 Process Data Object Mapping (Pdo Mapping); A 4.3.8 Service Data Sdo Service - MICRO-EPSILON interferoMETER Operating Instructions Manual

Appendix | EtherCAT Documentation
A 4.3.6 CANopen over EtherCAT
The application level communication protocol in EtherCAT is based on the communication profile CANopen DS 301. It is
called "CANopen over EtherCAT" or CoE. The protocol specifies the object directory in the controller as well as the com-
munication objects for the exchange of process data and acyclic messages. The controller uses the following message
types:
- Process Data Object (PDO). The PDO is used for cyclic I/O communication (i. e. for process data).
- Service Data Object (SDO). The SDO is used for acyclic data transfer.
The object directory is described in Chapter "CoE Object Directory", see
A 4.3.7 Process Data Object Mapping (PDO Mapping)
Process data objects (PDOs) are used for the exchange of time-critical process data between master and slave.
To transmit data from the slave to the master, Tx PDOs are used (inputs). Rx PDOs are used to transfer data from the
master to the slave (outputs); this concept is not used in the interferoMETER. The PDO mapping defines which applica-
tion objects (measurement data) are transmitted into a PDO.
The interferoMETER lets the user choose from a selection of Tx PDO mapping objects, see
In EtherCAT the PDOs are transported in sync manager channel objects. The controller uses the sync manager channel
SM3 for input data (Tx data). The PDO assignments of the sync manager can only be modified in the pre-operational
state.
Note: Sub-index 0x00 of the object 0x1A00 contains the number of valid entries within the mapping report. This figure
also represents the number of application variables (parameters) that should be transmitted/received with corresponding
PDO. The sub-indices from 1h up to the number of objects contain information about the depicted application variables.
The mapping values in the CANopen objects are coded in hexadecimal form.
The following table contains an example of the entry structure for the PDO mapping:
MSB
31 16 15
Index e. g. 0x6000
(16 Bit)
Fig. 79 Sample entry structure for the PDO mapping
A 4.3.8 Service Data SDO Service
Service Data Objects (SDOs) are primarily used for the transmission of data that are not time-critical, e.g. parameter
values.
EtherCAT specifications
- SDO services make possible the read/write access to entries in the CoE object directory of the device.
- SDO information services make it possible to read the object directory itself and to access the properties of the ob-
jects.
All parameters of the measuring device can be read or changed in this way, and measurements can be transmitted. A
desired parameter is addressed via index and sub-index within the object directory.
IMS 5x00
8 7
Sub-index z.B. 0x01
Chap. A 4.4.
Object length in bits,
e. g. 20h = 32 bits
Chap. A 4.4.1.7.
LSB
0
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