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InSource Solutions

TN DAS146 Configuring the MBTCP DA Server for Communication with a RTAC Device




This article from InSource shows how to configure the Modbus TCP DA Server from Wonderware for communication to a Schweitzer Engineering Laboratories RTAC-SEL3530 device.

  • Author: Rich Brooks
  • Published: 12/11/2016
  • Applies to: DASMBTCP v3.0 SP1


The RTAC device from Schweitzer Engineering Laboratories may be enabled for standard Modbus communication.  This article details specific configuration requirements for the Wonderware DASMBTCP device integration protocol.  Firstly, the port number needs to match what has been configured in the RTAC.  That is if the standard port 502 is not being used.  Changing the port number requires editing the configuration XML file.


A Modbus Bridge object is required as a part of the configuration underneath the port object.  Be sure to fill in the IP address for the RTAC.


Change the default Maximum outstanding messages from 2 to 1 to avoid repeated disconnects from the device.

The Modbus PLCRS object is added beneath the bridge object.  There are specific selections that are required for the RTAC device.  


This is displaying what worked for me, but some of these settings depend on how the RTAC has been programmed for Modbus.  You may use this as a starting point to test out the I/O communication.

The item addressing format used in Wonderware InTouch and Historian for this example configuration is listed below.


The analogs tags that span two registers need an L (signed) or U (unsigned) following the address number.