PROFIBUS DP Master Redundancy

Karlsruhe, January 2006 – The PRS, PROFIBUS DP Redundancy Switch, is a new addition to COMSOFT's product range and allows the trouble-free implementation of redundant DP Master systems.

Present PROFIBUS DP Master redundancy concepts are software based DP multi Master solutions, where the operational and the redundant DP Master exchange live information via the PROFIBUS line. In case of failure of the operational DP Master the redundant DP Master assumes the hitchless communication with the DP Slaves. This is only possible via the flying master algorithm, which means the redundant DP Master has to be parameterised to the PROFIBUS address of the faulty operational DP Master. This principle goes along with several risks: If the faulty DP Master does not disable its PROFIBUS bus traffic, a double address conflict occurs and the whole network will stop. A further disadvantage is the fact that many DP Master implementations on the market do not support the flying master algorithm.
Using PRS all these disadvantages no longer exist, because PRS generally prevents the DP Masters from simultaneously connecting to the PROFIBUS.

PRS is a compact 24 Volt hat rail module for the connection of two DP Masters as input and one PROFIBUS network connected to the DP Slaves as output.

PRS automatically detects the state of the two DP Masters. In case of failure of the operational DP Master, the device switches the PROFIBUS line over to the redundant DP Master within milliseconds. Both DP Masters can be configured identically, that simplifies the exchange of a defect system. PRS works with every standard PROFIBUS DP Master and also allows the simple upgrade of an existing plant for redundancy operation.

PRS is a double DP Slave that can be easily added to the DP Master's PROFIBUS configuration via its GSD file.
A failure of PRS does not cause a total breakdown because the current state is guaranteed even if the power supply is disconnected. This means the Slave communication continues in any event. Merely a switch to the redundancy system is no longer possible. Thanks to its modular structure, any of the electronic parts of the PRS can be exchanged, even without interrupting the bus traffic.

The device provides important information for the redundancy operation, i.e. the alive state of complementary system. On the command level, PRS can, for example, perform a manual switch-over command.
PRS also allows the realization of very complex redundancy systems, i.e. in connection with PROFIBUS OPC servers or overlying Ethernet based cell networks.