Overview

General overview

The TwinCAT 3 Parallel Redundancy Protocol enables real-time capable and redundant Ethernet communication via two separate networks. For this purpose, the Parallel Redundancy Protocol (PRP) according to IEC 62439-3:2018 is implemented and the prerequisite for using a PC with TwinCAT 3 as a so-called "Double Attached Node" (DAN) is created.

PRP is a protocol and method for redundancy of Ethernet at the MAC level (or layer 2), which is thus independent of the higher layers and protocols. The TwinCAT PRP Adapter used for this purpose implements the redundancy procedure in the TwinCAT real-time environment, as well as with a virtual adapter to the operating system, and can be used completely transparently for the system. All real-time capable protocols based on the TwinCAT Realtime Ethernet Adapter can communicate via the TwinCAT PRP Adapter. However, any non-real-time protocols and applications that communicate from the operating system via the drivers can also be used via PRP. For example, the real-time capable EtherCAT Automation Protocol can be used for redundant communication via PRP, as can the TwinCAT OPC UA server.

Components

The TwinCAT PRP Adapter requires two individual network interface cards (NICs), which are supported by the TwinCAT RT network driver (see system requirements) and can thus be integrated as TwinCAT Realtime Ethernet Adapters. These two adapters are then used for the interfaces to LAN-A and LAN-B defined in the standard.

Functionalities

The two network interface cards are combined via the TwinCAT Realtime Ethernet Adapter by means of the TwinCAT PRP Adapter to form a virtual network interface card in accordance with IEC 62439-3. The TwinCAT PRP Adapter can then be used to communicate redundantly via the two networks using PRP. This virtual network interface card then provides all the familiar functions and information as a real NIC. The two set network interface cards then act as a "Double Attached Node" (DAN) in the PRP network. It is still possible to use each individual TwinCAT Realtime Ethernet Adapter in TwinCAT as a "Single Attached Node" (SAN) and without PRP for communication via the individual network.

Since the use of PRP is completely transparent for the applications, the TwinCAT PRP Adapter has a corresponding diagnostic interface. This provides the necessary information for the evaluation of redundancy and all states.