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PRP-1 IP Core

The Redundancy Box (RedBox) is a switching device to connect conventional nodes (with only one network interface) to both LANs of a PRP network.

Because they appear to the other nodes of the network like dual attached nodes (DANs) they are called virtual dual attached nodes (VDANs). The mechanism of duplicate generation and duplicate rejection is completely transparent to the VDAN. The redundancy box completely mimics the nodes connected behind it and multicasts supervision frames on their behalf.

For management purposes the redundancy box itself can be a DAN have an IP address of its own and perform application functions.

A RedBox to connect a more than one VDAN has three network interfaces: one to each to the doubled LANs and one to the VDAN network.

A simplified version of the RedBox code can be used to enable an existing device to act as a RPR DAN. Instead of a network interface the device can be attached by dual ported RAM, a serial link or some other interface technology.

FPGA implementation

ZHAW offers an implementation of the Parallel Redundancy Protocol (PRP according to IEC 62439‑3 / 2012) as a VHDL IP core.


The ZHAW PRP-1 Core is an IP to implement a PRP Redundancy Box (RedBox) on a FPGA. It is designed to be ported easily to different platforms. Version 1 of the PRP protocol is implemented, which is not compatible with the older version of the standard (called PRP-0 or IEC 62439‑3 / 2010).


The PRP-1 Core is interface-compatible with the ZHAW HSR Core, sharing a big part of the code base. PRP-1 requires fewer FPGA resources, but shares some of the HSR specific infrastructure.


The delivery consists of:

In order to run the reference implementation a suitable hardware kit is available. The board is delivered as a ready to run PRP RedBox. It is equipped with a Cyclone III FPGA, four Ethernet PHYs, RAM and Flash. The NIOS II softcore CPU (with MMU) provides basic functions such as initialization of the device and sending supervision.

The documentation includes a quickstart guide and a detailed manual. The quickstart guide describes the reference implementation, how to rebuild it and how to run the testbench. The manual describes the Core interfaces, the process of porting to a new platform, the purpose and working of internal modules, the register set and most of the internal signals.


The ZHAW PRP Core provides a byte-oriented signal interface to connect to 100 Mbit/s full-duplex Ethernet. To connect to a standard PHY, a conversion to MII is provided. To connect to the CPU for supervision, management, and link-local protocols, a Wishbone interface is provided.

The reference implementation is shown below.

Configuration Variant

The IP Core can be configured to use FPGA-Internal RAM. It is also possible to use an external CPU connected via Ethernet. However the CPU still needs access to the registers of the IP Core.