EtherCAT Motion Bus Concepts
To exchange data between the controller (master) and the devices (slaves), the KAS RuntimeIn computer science, runtime (or run-time) describes the operation of a computer program, the duration of its execution, from beginning to termination (compare compile time).
Within KAS, runtime also refers to the virtual machine that manage the program written in a computer language while it is running relies on
In cyclic mode, a single frame containing the data of all slaves (input and output) travels along all slaves and goes back to the master. Data is read and/or written "on the fly" by each slave.
Slave device input and output data definitions:
- Outputs are written by the master and read by the slave device
- Inputs written by the slave device and read by the master
This cyclic frame is called the EtherCAT Process Image. It contains the Process Data, which is defined during network initialization.
The cyclic data is grouped in predefined blocks called Process Data Objects or PDO.
If you want more in-depth information on EtherCAT, you can read the following chapters:
-
-
PDOs contain real-time cyclic data which is deterministic. Non-cyclic data is not deterministic and is defined by Service Data Objects (SDO).
References
- EtherCAT Specification V1.0 - refer to http://www.ethercat.org ( in Member Area - Downloads)
- Büttner, H.; Janssen, D.; Rostan, M. (2003), EtherCAT - the Ethernet fieldbus, (PDF), PC Control Magazine 3: 14-19