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Old March 27th, 2008, 04:46 PM   #1
broadleaf111
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RSLogix 5000: More than one Generic Ethernet Module To The Same IP Address

Hello,

I'm using a ControlLogix controller with 1756-ENBT to communicate with an I/O adapter using EtherNet/IP. RSLogix 5000 v13.03 is being used to program the controller. I've successfully configured a Generic Ethernet Module to communicate with an input/output assembly pair on the adapter. There are additional input/output assembly pairs on the adapter with which the controller needs to communicate, but when I attempt to configure a second Generic Ethernet Module with the same IP address as the first, RSLogix complains of an "Invalid IP Address".

Is there any way to create more than one Generic Ethernet Module to the same ip address?
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Old March 27th, 2008, 05:05 PM   #2
robertmee
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Not sure I'm following your question...

Are you saying you have an ENBT in a CLX Rack, and then multiple IP aware adapter modules on the network and are trying to communicate to them all?

If so, multiple adapters cannot have the same IP address. They must be unique. In your CLX setup, you would right click on the ENBT Module (or Ethernet under it) and Add new module. Pick generic and give it a UNIQUE IP address for each one. On any TCP/IP network, all devices must have unique IPs. Otherwise, it wouldn't know which one to talk to.

If you are trying to pick up additional I/O on that adapter, then expand the I/O size in the configuration of the Generic Device.

What adapter are you trying to communicate to?
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Old March 27th, 2008, 05:16 PM   #3
Gil47
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Are you talking about using 1 ENBT or ARE there 2 ENBT modules you are referring to, as 2 modules require 2 different ethernet addresses
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Old March 27th, 2008, 05:29 PM   #4
broadleaf111
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There is only one IP aware adapter module (thus the single IP address). The following assembly instances exist on the adapter module:

100 - input
101 - output
102 - input
103 - output

I'd like the CLX to have access to the data in both input assembly instances 100 and 102, and to be able to write data to the attributes in both output assembly instances 101 and 103. I tried to create two Generic Ethernet Modules with the same ip address, one configured for input assembly instance 100 and output assembly instance 101, and the other configured for input assembly instance 102 and output assembly instance 103.

The adapter I'm communicating with is a PC program emulating an EtherNet/IP adapter with a EtherNet/IP protocol library. More data needs to be exchanged between the adapter and the CLX than can fit into a single assembly instance (because of the ~500 byte limit.) I was hoping I could circumvent this issue by dividing the data amongst multiple assembly instances.
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Old March 27th, 2008, 05:31 PM   #5
broadleaf111
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Hi Gil47,

Sorry my original post wasn't very clear. There is only one ENBT and only one EtherNet/IP aware adapter module w/ which the CLX needs to communicate.
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Old March 27th, 2008, 06:05 PM   #6
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What are these input/output assemblies?
You can add second In/Out Assy instance if you select DATA DINT - WITH STATUS
But this all looks very strange. Get sample code from manufacturer!
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Old March 27th, 2008, 06:39 PM   #7
TWControls
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A little more detail on what you are communicating with or what is actually mapped to the assemblies would be nice. But I've had to do this before. Map time critical I/O to the assemblies under your module configuration.

The use messaging to read none critical information from the other I/O assembly. I don't have anything in front of me but it should be something like this

SetSingleAttribute
Class 4
Instance 103
Attribute 3

GetSingleAttribute
Class 4
Instance 102
Attribute 3
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Old March 27th, 2008, 07:27 PM   #8
broadleaf111
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Thanks for the suggestion. I might have to implement this type of hybrid communication model, but I was hoping to implement this with I/O communication only.

I was able to configure two Generic Ethernet Modules to communicate with the same adapter module by configuring them with two different host names, and then configuring a DNS server to resolve those two host names to the same IP address. This worked very well, and showed the CLX is capable of establishing multiple I/O connections to the same adapter, but it isn't a viable solution because of the additional complexity of maintaining a dedicated DNS server. Given the results of this test with the host names, it seems a bit odd that RSLogix would prevent configuration of multiple Generic Ethernet Modules with the same IP address, so I was hopeful there was something I didn't understand here, and a way I could get this to work without DNS tricks or a hybrid communication model.
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Old March 29th, 2008, 06:25 AM   #9
TWControls
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Quote:
Originally Posted by Contr_Conn
What are these input/output assemblies?
You can add second In/Out Assy instance if you select DATA DINT - WITH STATUS
But this all looks very strange. Get sample code from manufacturer!
I had never thought about using the Status tag, good idea. But I only see how I could map an additional Input assembly. How would you get the additional output assembly?
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