Device operating modes
A POWERLINK-capable device can handle the following operating states.
Basic Ethernet mode: The device is operated directly in the existing Ethernet networks, when real-time data transfer is not necessary. This is the default operating mode after switching on the device.
POWERLINK Mode: After completing the boot procedure, the device enters real-time operation. The managing node checks the timing. The cycle time depends on the amount of isochronous and asynchronous data, as well as the number of nodes. The basic cycle consists of the following phases:
- Start Phase - All nodes synchronize themselves to the managing node
- Isochronous Phase - The managing node assigns a fixed time window to each node for transferring transfer time-critical data. All other nodes can always listen to all data during this phase (publish/subscribe).
- Asynchronous Phase - The managing node frees up the network for a particular node to transfer data that is not time-critical, e.g. parameters and diagnostics data. Standard IP-based protocols and addressing are used during this phase.
The quality of the real-time behavior depends on the precision of the overall basic cycle time. The length of individual phases can vary as long as the total of all phases remain within the basic cycle time boundaries. Adherence to the basic cycle time is monitored by the MN. The duration of the isochronous and the asynchronous phase can be configured.