Micro820 to MicroLogix 1100 Modbus Communications

coopdegrace

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Join Date
Mar 2009
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perth
Posts
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Hi All,

Just wondering if anyone can offer some help or point me in the right direction in regards to Modbus communications between a Micro820 and ML1100 PLC.

I have no hardware for testing at this stage and limited experience using CCW so I can only make assumptions...

What I want to do is pass data from a ML110 to a Micro820 via Modbus RTU then read this and additional data from the Micro820 by a PC via Modbus TCP/IP.

From my limited knowledge I have figured that the Micro820 has a Modbus Map that could be written to by the ML1100 over Modbus RTU using MSG commands I could then set up a PC to read data from this same Modbus map using Modubs TCP/IP.

Before going out and buying the hardware I just want to confirm this is the right way to do it as I wont have a lot of testing time.

Any suggestions and information as to how to set this up would be much appreciated.

Cheers All
 
If you are going to use an Ethernet compatible Micro820 then why not communicate to it (from the MicroLogix 1100) via Ethernet? I also don't see any reason why you would need to use Modbus TCP unless you are using a software program that only uses Modbus. Allen Bradley products use EtherNet/IP as their native Ethernet language and while they can use Modbus TCP there isn't an advantage to doing so.
 
To be honest I didn't know Micrologix 1100 was Ethernet capable. Ill have a look into how to achieve this but any info that may help would be appreciated. Is communications easy to set-up between the two?

My question is (and sorry if its a stupid one) will the Micro820 be able to communicate with the Micro 1100 via Ethernet IP and to the Linux machine via TCP out of the same port at the same time?

The reason for using TCP is because we will be communicating to a linux based machine with propriety software that has already been developed.

Thanks for the help.
 
That one is over my head. I’m an Allen Bradley guy and if you were looking to communicate via EtherNet/IP then yes, it is very easy but adding Linux to the equation means someone else will have to jump in. I think it should still be doable, but I have no idea how.
 
Thanks Firejo,

Just wondering what the best way would be to communicate between the Micro820 and ML1100?

Would you use CIP read and write?

Cheers
 
In my knowledge, there is no way to do an Ethernet connection between a Micrologix 1100 and a Micro820. Micrologix doesn't support CIP messaging. I believe both can be a Ethernet/IP Client but you'd need a Ethernet/IP Server on another PLC.

I could suggest the following to you...
The Micrologix 1400 Series B does have Modbus TCP (Server/Client) capabilities (ML 1100 and ML1400 Ser A don't).
I used this configuration on one project and it worked well. As you described earlier you can set up a Modbus Map in the Micro 820 then Read/Write to that with Messaging in the Micrologix 1400.
 
sbaum's correct, that one got past me. The MicroLogix 1100 is an EtherNet/IP PCCC device and the Micro820 is an EtherNet/IP CIP device. It should be possible to do a generic CIP message instruction but the setup on that is complicated and probably not worth the effort.
 
Unfortunately we already have the hardware.

I will try get the generic CIP messaging working but i am not holding my breath.

Anyone set this up before?

Next option would be to use serial connection

Thanks again for the help
 

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