Modbus is a protocol for field bus systems using the Master/Slave principle. Modbus Slave and Modbus Master communicate with each other, whereas information is exclusively exchanged via (Modbus) registers. A Modbus Master reads the Registers of the Modbus Slave at regular intervals (polling) to be able to act on status changes.

Modbus TCP extends the transmission of Modbus telegrams on the network layer, where the telegrams are exchanged via a connection-oriented TCP link. The communication is based on the Client/Server principle. The Modbus Client can be compared with the Master. The Modbus Server can be compared with the Slave.

Every INTRON-D plus node offers an integrated Modbus TCP interface which can be used to control dedicated functions inside the INTRON-D plus.

The main applications are managing control lines (I/O functions, set & reset control lines, etc.) and warning control (start & stop warnings, request handling, change warning phases, etc.).

This range of possibilities is often used for integrating warning and evacuation functions into customers’ SCADA applications so that it is possible to activate control lines or alarms using the GUI of a SCADA system.

If the Modbus TCP interface is activated, it operates as Modbus TCP Server. The advantage of this is the very fast response time of the INTRON-D plus to the events triggered by the Modbus TCP Client. Modbus TCP Client connections are also monitored. A loss of the Modbus TCP Client connection can be indicated at different targets (SNMP & SMTP interface, master intercom station, etc.).

The INTRON-D plus configuration software Config Manager provides an easy way to configure the Modbus interface for the integration into SCADA applications or existing Modbus TCP environments.

For more information on how Modbus is used in the INTRON-D plus and the Config Manager from INDUSTRONIC, please click on the PDF link.

Also visit the www.modbus.org website to find a detailed description of the Modbus protocol.