M340 Modbus plus proxy

[AllanWang]

I am working with a plc migration job from Momentum to M340 in which the BM+ peer cop ( specific input

and Output) used.  So I need to add the MB+ proxy unit to comm with the remote MB+ IO. 

Need to verify something before to buy the unit, I here have questions for seek expert to help: 

Q1.  Reading the manual to configuration the proxy unit, In the offset table, the souce or destination %MW

        are belong to Proxy unit or M340 PLC ? 

Q2.  Do I need to do the program (Read_Var or Write_var or IO scan) for M340 to get the data From IO ? 

Q3.  If the %MW belongs to M340, so I do not need to do program. Is the remote IO data will automatic go to 

       M340 PLC %MW as the offset configured in proxy configured once the ethernet com established? 

Best Rewgards 

[dnordenberg1]

Hi!

First I have to say I'm no expert in MB+ or momentum but I don't think you need any special proxy hardware. I guess you will need to change the IO hardware anyway later once the code is migrated to the M340? Then just use the momentum CPU as a proxy/gateway. If you dont you will most likely run into troubles with output modules because you can't control them from different PLCs. Instead expose the in/output IOs through Modbus TCP or RTU to the M340 from which you then IO scan or use read/write_var as you say.

You don't describe exactly how you intend to to the migration but it sounds like you want to do it "online" function by function or object by object? Then I think what I described above is the best. For each output IO you move to be controlled by the M340 instead you will have to map the adress coming from the M340 to the IO in your momentum program.

And by the way, I think there is a way to convert your momentum project (which is in PL7 I guess?). There is a software called UMAC that can do that, it does cost some for the full feature version and it needs Control expert XL which is way overkill for M340 but talk to your Schneider representative, maybe they can help you out with the converting step so you don't need to buy it for a single use.

[dnordenberg1]

And I would advise against using a M340 today, it is much older and less powerful than a M580. And a M340 could cost you more because you can't do IO scanning with the CPU ethernet port, you need a expensive NOE for that which actually cost much more than the CPU itself. With M580 you get IO scanning straight out of the box with the smallest CPU. M340 is not obsolete, it just isn't as future proof as M580 and there is often no good reason to use M340 over a M580. M580 can also do more modern protocols like Ethernet/IP. In a M340 you would need another expensive extra module for that...

[AllanWang]

Hi. Thank you reply 

May be I have not explain my case clearly. 

The existing Mometum installation include One main panel ( composed the Momentum CPU and Modbus plus

peer cop master) and 5 momentum modbus plus remote IO drop panels.  These total 6 panels are around 200

meters from the main panel to last. Customer request to replace the momentum CPU to M340 in main panel

and remain the momemtum modbus plus IO in the 5 remote panels. So that will save cost of no change remote

IO and not lay new cable ( reuse modbus plus cable ).  That is why the M340 modbus plus proxy to be used. 

 I here have questions for seek expert to help: 

Q1.  Reading the manual to configuration the proxy unit, In the offset table, the souce or destination %MW

        are belong to Proxy unit or M340 PLC ? 

Q2.  Do I need to do the program (Read_Var or Write_var or IO scan) for M340 to get the data From IO ? 

Q3.  If the %MW belongs to M340, so I do not need to do program. Is the remote IO data will automatic go to 

       M340 PLC %MW as the offset configured in proxy configured once the ethernet com established? 

[dnordenberg1]

Q1 We can't guess without more info.

Q2 Same here, it depends on how your "proxy" works, if it will be a Modbus slave or master.

Q3 Probably yes, if it is the master but that is not the usual case, PLC usually is the one that is polling for data. In the case you describe, how will you know the proxy is writibg data and the IO status is current? You will have to handle that manually somehow with a watchdog or something, you can't get that info directly somewhere like from the IO scanning or read/write_var then.