Modbus TCP or Allend Bradley EthernetIP?

Ignition
1

In most cases I would go for the OPC-UA support of the AB EthernetIP device but I am wondering if anyone can suggest why it would be better to use one or the other? Speed? Efficiency? Reliability?

2

What device are you connecting to? It’s usually better to go with the device’s “native” protocol.

3

Interoperability.
LOTS of things are capable of talking Modbus TCP.

EthernetIP is great with devices that talk it though!

4

Micrologix 1400 will be used.

I agree with both of you just trying to see if there was any documented evidence for one over the other. Like write/read time, number of messages to accomplish the same task, etc.
Thanks.

5

[quote=“techerdone”]Micrologix 1400 will be used.

I agree with both of you just trying to see if there was any documented evidence for one over the other. Like write/read time, number of messages to accomplish the same task, etc.
Thanks.[/quote]

well, if I remember correctly, if you use modbus tcp on the 1400 you will have to pack all of your values into the data files that you tell the channel configuration to use for each respective modbus code. so in that respect, you may have to do more programming work. I believe you can do both at the same time also, ethernet/ip and modbus tcp on the same 1400.

6

I would just use the native protocol of the A-B controller.

Because the MicroLogix 1400 uses the classic A-B style “typed data tables” it’s just as efficient as Modbus/TCP.

Organize your Ignition data into dedicated data tables (one for Integers, one for REALs, one for Strings, etc) and you’ll get the best results.

As mentioned above, you can run both the native EtherNet/IP protocol and one other protocol simultaneously on the MicroLogix 1400 Ethernet port; you choose either DNP3.0 or Modbus/TCP.

7

Just thought I’d mention that the limitation I have found with Modbus TCP for the micrologix is that you are limited to only binary and integer data types. No floats or longs!

Also, there is a 5 data file limit for the holding registers. So 1280 ints in holding registers. Binary has a 4096 limit for either type of binary modbus register.