Allen Bradley CPU data direct via Moxa EIP 3270

I am trying to read data from an SLC cpu using a Moxa EIP3270. I can get data out by having the moxa software set to a virtual com port, read this into RSLinx and then have RSLinx as an OPC server but is there a way to read the CPU direct with Ignition - Am I missing something obvious?

I haven’t used the product, but it appears to be a serial to Modbus gateway. Perhaps you could connect with the Modbus driver.

Actually no, the model I quote “EIP” is Ethernet IP not the modbus variety. The intention was to be able to access a SLC direct from the EIP3270 into Ignition. I can set it as a TCP device and the connection reads OK but this is obviously the incorrect method of connecting to a PLC. Anyone got any ideas?

If you are using a virtual com port then your are using DF1. The Inductive AB OPC-UA driver supports Ethernet/IP not DF1. The Moxa should be able to do protocol conversion between Ethernet/IP and DF1. First try reconfiguring your RSLinx and get it talking using Ethernet/IP ( no virtual COM port used) . Once you get this working, then shutdown RSLinx and try a similar setup with Inductive’s driver.

Cannot get this into Ignition. RSLinx sees it and RSLogix500 will go online (using Ethernet not Ethernet/IP driver). Have tried setting it as compact logix and micrologix, both say connected but neither will browse the data files.

Have you talked with Moxa about using Ethernet/IP with RSLinx to a DF1 SLC?

The only 3rd party serial to Ethernet adapter mentioned in the Inductive manual is the Spectrum Controls WebPort 500 which like the 1761-NET-ENI is a Ethernet/IP device, not AB Ethernet (CSP).

There has been a lot of chatter about connecting to processors through an Ethernet to serial conversion unit. So, I thought I would provide some information on the topic.

The OPC-UA SLC driver supports multiple protocols and the protocol is determined in the following way:

  • If the connection path is blank (empty), it will first try CSP protocol on port 2222. If an error is received it will then try EIP protocol on port 44818 (this is the protocol used for the NET-ENI interface). The driver will keep trying each protocol until a successful connection is made.

  • If the connection path is used, the driver will use only EIP protocol on port 44818 and is intended for connection through a DHRIO module residing in a ControlLogix gateway.

Serial DF1 protocol is not supported, so a straight Ethernet to serial converter will not work with the OPC-UA SLC driver. The device must support Serial DF1 protocol for the serial connection to the processor and either CSP or EIP on the OPC-UA side. Although, CSP is typically only used for a processor directly connected through Ethernet.

We have customers that are using Moxa and it works fine to communicate to both the SLC and MicroLogix processors. I am finding out the model number of the Moxa unit and will post in this forum.

Usually, it is a matter of configuring the unit for the correct protocols, station numbers, etc.

I heard back from a customer that is using the Moxa with our OPC-UA SLC and MicroLogix drivers. He is using the Moxa 3270 which is a Ethernet/IP to DF1 gateway.

thechtman - Do you know if they are using the EIP3270 directly into Igntion, without using RSLinx as an OPC etc. Currently I can see the Moxa device in RSLinx, with the Ethernet driver, displayed as a CPU, with the Ethernet/IP driver it displays as an unrecognised gateway BUT both drivers let RSLogix500 go online. In Ignition if I set the device as an SLC it shows disconnected almost straight away. If I set it as a micrologix or compactlogix it shows connected but hangs on a browse and finally comes back empty. If your customer can use the Moxa direct there must be a setting (or routing table???) I have not configured but I am baffled!

A quick update, we ordered a Moxa so that we can test in-house. I’ll keep you updated.


Another update: the issue preventing connection through a Moxa EIP 317x protocol converter has been resolved. This affects the SLC and MicroLogix drivers in OPC-UA.

The next beta or release will contain the fix.

Thank you,


Oops, Moxa EIP 3x70