Introduction

Network variables are variables that can be exchanged cyclically between TwinCAT controllers via real-time Ethernet. Variables with any data types, including complex types, can be exchanged. The Publisher/Subscriber model is used. For highly deterministic communication, the real-time Ethernet driver for TwinCAT must be installed.

Publisher/Subscriber model

In the Publisher/Subscriber model, the Publisher provides variables. Subscribers can subscribe to a variable. The Publisher can make the variable available to one Subscriber, several Subscribers or all Subscribers. In Broadcast mode the variable is made available to all PCs, in Multicast mode to selected PCs and in Unicast mode only to one selected PC. A Subscriber can also be Publisher at the same time. This also allows a bidirectional data connection to be established.

Unicast

The Publisher makes the network variable available to a single selected PC.

Multicast

The Publisher makes the network variable available to selected PCs.

Broadcast

The Publisher makes the network variable available to all PCs.