Communication Using BM 85

  • Thread starter P. Soundararajan
  • Start date

Thread Starter

P. Soundararajan

How does communication takes place among modbus devices connected to various ports of BM 85 Bridge Multplexer. Specifically three modbus devices are connected to three modbus ports, one is master. Modicon Compact PLC is connected to Modbus lus port. How does the master device receives data and sends commands to the other devices. How a device is assigned as a master and how does master initiates communication? Does each register in the master to be assigned slave register address/s so that the communication takes place register to register? Is there any detailed document/paper available in this regard.
I suggest that you review the BM85 manual and then most items will be clear. Email me your email address and I can send manual. I am at [email protected].

BM85 is a protocol convertor. Modbus Plus to Modbus RTU or ASCII. You can go from Modbus to Modbus Plus or from Modbus to Modbus. The modbus ports support Master or Slave devices.

Configuration is done using Hyperterminal from Windows and is saved in flash in the BM85.

Most applications are quite simple to configure.

Robert Willis

The Modbus Plus Network BM85 Bridge Multiplex User's Guide (Part Number: 890USE10300) has the answers to all of your questions. You can download the manual from "": .

Instructions for the MSTR Instruction which allows the PLC to communicate via the Modbus Plus port are inlcluded with the Programing software. (Modsoft or ProWORX NxT). If you are using the Concept Software package (IEC-61131-3) then you have some other function block options for communicating via the Modbus Plus Port of your controller.

Robert Willis
Square D Company
Houston, Texas