Ethernet I/O


Thread Starter

Kaufman, George

We are looking at using Ethernet I/O in a machine control application.
Can anyone comment on actual experiences with Ethernet I/O? What is the most common protocol with Ethernet I/O? Which suppliers of Ethernet I/O are the leaders?

Best regards,
George Kaufman

Robert Willis


There are numerous suppliers of Ethernet I/O and all of them seem to have various TCP/IP protocols that they support. Check out the Modicon Momentum Product Line which supports the Modbus TCP/IP Protocol.

Robert Willis
Try Beckhoff
They have a standard i/o module with an ethernet extension

Met vriendelijke groeten,

Onno Moret

Imtech Projects West
Control Systems

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of the company.

Marcos Giorgianni


Today, some companies are using ETHERNET I/O just to collect process data and send them to a data base.

The most common protocol is TCP/IP and you can look at:

Best regards,


Raoul Huisman


There are a lot of Ethernet IO suppliers. You can divide them into two separate suppliers:
1. Remote IO (No intellegence)
Check out Opto 22 modules called SNAP Ethernet I/O
Sixnet IO Ethertrack modules (
2. IO and Local Intelligence
We use the Momentum IO bases from Schneider Electric, works fine.

Best regards
Raoul Huisman

Curt Wuollet

Hi all

The Ethernet Brain supports a block transfer proto somehow related to firewire. It supports five (5) modbus/tcp commands. Twice I have been working with their customer service on how to do
cyclic IO for the Linux PLC. Twice I have been forgotten. You might take a look at Sixnet or Optimation before you pick one.



Helmut Wieneke


there is a solution from Phoenix Contact Germany. They offer an ethernet gateway to inline I/Os. It is named FACTORY LINE INLINE BUSCOUPLER (FL IL BK). The I/Os are very fast and scalable for
different applications.

Best regards
Helmut Wieneke

Mike Wehrenberg

Ethernet I/O is a very interesting topic these days. Not only because of the vendors who are connecting control system I/O to ethernet but because of the unique issues that having ethernet I/O on a machine control system pose to the engineer responsible for the control system.

There are a number of vendors with I/O connected on ethernet: Modicon with their Modbus TCP, Opto 22 with their SNAP I/O, National Instruments, etcetera. These vendors are using TCP/IP as
the stack protocol to make the link connections but TCP/IP does not specifiy how or what the actual data inside the TCP/IP message packet means. So, each vendor defines this application
layer definition of data in what they believe is a useful and sellable embedded protocol. What this essentially means is that Opto 22's
ethernet I/O will not talk to a Modbus TCP system or National Instrument's or whomever's.

There is a consortium of control and networking vendors who can be reached at They have developed an
open control and information protocol (CIP) that rides on top of TCP/IP ethernet packets and defines the control and useage characteristics that we need as control engineers to use ethernet
as a control network. This control protocol stack is called EtherNet/IP which stands for "Ethernet Industrial Protocol". This protocol defines implicit I/O message formats for I/O points and
defines explicit message formats that allows control program monitoring, upload/download, and PLC to PLC messaging capability. It utilizes the extremely common TCP/IP and UDP (User Datagram Protocol) stacks as the delivery mechanisms for these CIP control packets. Please visit to get more information. One of the vendors in the EtherNet/IP camp is Allen Bradley (along with a few others like Mitsubishi, OMRON, Interlink BT, and many others). They are using this CIP on TCP/IP - UDP as their standard for ethernet I/O. Their first products are in the testing stage and are expected this late fall - early winter time

In spite of the work that various vendors and the EtherNet/IP consortium are doing to utilize ethernet for connecting I/O to the control system, there are a number of issues that just the
"physical" use of ethernet to connect I/O presents: 1) Ethernet is fast and almost always fast enough to do machine control. But it is
NOT deterministic. Every node can talk whenever it wants and collisions can and do occur. 2) Wiring of ethernet with unshielded twisted pair cable on the plant floor with high current sources of noise, vibration, temperature, grounding problems, capacitive coupling of conduit and multiple conductors in a raceway, etcetera.
a - The RJ45 jacks may not last as long as we'd like (there is a
spec to put a MIL twist-on connector around the RJ45 jack)
b - Noise, frequency response, signal degradation can all play a
role in stable ethernet communications
c - Ethernet transceivers of "industrial" plant floor quality 3)
Isolation of ethernet "hogs" like server PC's, and CAD stations, and broadcast messages, and the like from the control system ethernet nodes needs to be considered.

These are just a few of the design issues that need to be thought about when using ethernet as a control network. These issues can be overcome. You just need to make sure you use the proper
wiring, ethernet switches, cable layout, node isolation, etcetera. So, obviously time will tell who will win this ethernet I/O bus
bet is that Ethernet/IP with the comprehensive stack protocol that defines all the needs of a robust control network will be a major player.

Mike Wehrenberg
Kendall Electric
Battle Creek, MI
616 963-5585

Matthew Lamoreaux

Industrial Ethernet for Control was the title of an ISA technical conference held in Cleveland this past May. Many of these issues were discussed. Here's a link to some news from the conference:,1771,1092,00.html. ISA will be hosting another conference on Ethernet in Houston this December. More
information is available on the ISA web site at:

Matthew Lamoreaux, Associate Editor
Industrial Computing magazine
ISA - The Instrumentation, Systems, and Automation Society
E-mail: [email protected]
Industrial Computing Online:
Web site: