If necessary, a DP slave can also exchange data directly with another DP slave. This function is called direct data exchange.
This direct data exchange is one of the DP-V2 protocol extensions and is optional. Implementation is with the MSRD service.
In the case of direct data exchange, the class 1 DP master (MC1) sends output data to a DP slave. The latter responds with its input data, which it sends to all (broadcast). This DP slave is thereby designated as a publisher. Further DP slaves can now work as subscribers, by subscribing to this published data.
In the standards, this function of direct data exchange is known as Data Exchange Broadcast.
The following sections will explain in more detail the conditions and functions of publishers and subscribers.