Controllogix Redundant Modbus

Hi All,

Need to configure "Redundant Modbus" but having issues.
I have a Redundant Controllogix setup with the following configuration -

RACK-1 (7-Slot) (Primary)

1. Processor L73
2. Controlnet CN2R
3. Ethernet EN2T
4. Redundancy RM

RACK-2 (7-Slot) (Secondary)

1. Processor L73
2. Controlnet CN2R
3. Ethernet EN2T
4. Redundancy RM

RACK-3 (IO-1) (13-Slot)

1. Controlnet CNBR
2. IO cards.......all slots

RACK-4 (IO-2) (13-Slot)

1. Controlnet CNBR
2. IO cards.......11 slots
13. Slot-12 (Last Slot) MVI56E-MNET

The Task is to configure "Redundant MODBUS"

Initially the MNET cards were placed one (1) each in Redundant chassis but
were removed and one (1) card placed in RACK-4 last slot.

My questions are -

1. Can we place the MNET cards in Redundant Chasis (I am aware that only CNT/ENT cards are allowed in Redundant Chassis) ?
If no then how can we achieve Modbus "Redundancy"

2. With the above setup i tried to configure the MODBUS card by directly connecting an ethernet cable to the configure port and tried following User Manual but the MNET card gives an error 412 saying the processor cannot talk to the MNET card. I cant even upload the configuration from MNET card directly through its configure port.

How do we configure the cards ? Should we place a processor and MNET card in an empty chasis, configure and then re-arrange for original configuration ?
Is there any other way to configure the card so that MODBUS data can be sent through one card atleast.

I think that you will need MVI56-MNETR in a remote rack. I suppose you could use a pair of them with logic in the processor to switch from one to the other in the event of x bad responses.
Have you tried contacting Prosoft's technical support. It's free and they've always quickly resolved the problem when I've used them.

FluxCap said:

I think that you will need MVI56-MNETR in a remote rack. I suppose you could use a pair of them with logic in the processor to switch from one to the other in the event of x bad responses.
Have you tried contacting Prosoft's technical support. It's free and they've always quickly resolved the problem when I've used them.

Click to expand...

Thank you FluxCap.

Nothing from Prosoft since almost a week now. Their support may not be good in this part of the world.

How do we generally configure these cards ? First do we configure using an empty chassis with Processor and MNET and after configuration install as per PLC Architecture design ? When i tried to configure through Controlnet Setup it was giving error. Not sure where the problem is.

I have limited access to the hardware as i am off site currently.

Thank you.

This is a difficult problem for several reasons.

You cannot place the MNET modules in the chassis with the CPUs and the Redundancy Modules. You are correct that only CPUs, Redundancy Modules, and network modules can be in those chassis.

The MVI modules are notorious for having a large data block that is difficult to fit into a ControlNet schedule. That is why the reduced-data-block "MNETR" version was developed.

When you say that you want "Redundant Modbus", do you mean that you want a single Modbus/TCP connection to a ControlLogix Redundancy control system, or that you want two Modbus/TCP modules that can act as backups to one another ?

Focus on getting the MVI56E module accessible to your configuration and troubleshooting tools first, then work on fitting it into the ControlNet schedule and the ControlLogix Redundancy architecture.

Agree with others, placing 2 cards in 2 separate remote racks is the ideal solution.

You should be able to load the configuration to each card directly through its config port. I remember running into errors in loading the configuration, you have to first assign an IP to the card then load the config; if I recall correctly I think you have to use a crossover cable.

Not necessary but you may want to remove the chassis from the network (if you can) containing the Prosoft card while you're loading the config the first time as a precaution.

Thank you Ken Roach & EarthRocker for the replies.

Does that mean that i wont find any success trying to configure MVI56E-MNET (large data block) instead of MNETR card ?
The MODBUS Data needs to be redundant, meaning if one card fails the other should be able to send data to the client.

While trying to configure the MNET card directly i was able to change its ip (temporary ip) and communicate without any issues. But uploading/downloading configuration from PCB was giving an error 412 saying the card cannot communicate with processor. I did download the MNET AOI blocks etc (as per manual) in the original program(redundant/controlnet) but only through original setup, not in a seperate/empty chassis setup.

i have used MCM modules before, but not on redundant systems and there wern't many problems.

Any more suggestions ?... please....