Micrologix and DualPro modbus RTU

[MachinePLC]

Hi There,

I have a problem to conect DualPro instrument (from Maratho Monitors) with a micrologix 1200, somebody have an idea to start this project,
The protocol to comunication is a Modbus RTU

thanks

 

[OkiePC]

Modbus RTU Master Driver is available on ML1200 processors (Series C FRN 8 or later).

If you have a techconnect contract with a/b, here is a good technote.

Paul

 

[plclatin]

MachinePLC:

If this is your first time using Modbus RTU, here I have some advice:

1) Get the manual for Micrologix Communication. As OkiePC said, check you have the right firmware, if not flash the PLC to upgrade it.
2) Get the serial port pinout for the Micrologix and the cable. Be sure which is A, B and ground. Sometimes would be confusing as in RS485 A is also (-), and B is (+).
3) Because the communication is event type, if something doesn't work it could get very frustrating. The best is also to have a RS232 to RS485 converter, plus a virtual Modbus Master and virtual Modbus slave, which are software. In this way you make sure you are sending information to the right registers.
4) Make sure you have the right register map. Sometimes different manufactures have a diferent notation. For Instance register 40001, for some manufacturers would be register 0, or 1. So is very easy to miss that.

Saludos cordiales.