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Is there a way to find out what IP address the BOOTP server assigned to the NOC module?

Published date: 30 March 2021

To retrieve the IP address of the BMENOC without knowing in advance what it is, a READ_VAR request needs to be sent :


1- The configuration of the character string of the ADDMX should follow this rule : 'r.s.c{}TCP.MBS' , with :

  • r : rack number of the BMENOC
  • s: slot number of the BMENOC
  • c: channel to be used to communicate with BMENOC

In my example , my BMENOC is located in slot 3 of rack 0 , the string is '0.3.0{}TCP.MBS'

Then the IP address used is the loopback IP address of the BMENOC module: .


2- The output variable of the ADDMX block needs to be modified , as by default the UnitID parameter of the ADDMX_TYPE is 255.

To retrieve data using the looopback IP address of the BMENOC, this Unit ID must be set to 100.

The array format of the ADDM_TYPE is :

This means the Unit ID parameter is the High byte of the ADDMX[3] variable.

3- Then send a modbus request to the BMENOC with the following parameters :

  • Enable : trigger
  • ADR : ADDM_TYPE with Unit ID =100
  • OBJ : 'MW'
  • NUM : 5
  • NB: 2
  • GEST : exchange management array of 4 INT, do not forget to define a timeout (3rd INT of the array)

Example :


Result :

with RECP_NOC[1..2] containing the IP address of the BMENOC in hexadecimal format ( C0 A8 0A 0A => 192 168 10 10).
The IP address of the BMENOC is


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