How to add Ethernet to a SLC-500

SLC-500 FamilyThe SLC-500 is a very popular PLC with over a million installed processors in facilities around the world.

Over the years many of those facilities have modernized their sites by adding plantwide ethernet networks, and I often get calls asking how they can add their legacy SLC-500 systems to those Ethernet networks.

Note: For our previous articles on adding the Ethernet to the PLC-5 or MicroLogix, see the links below:

Native Ethernet with the SLC-5/05

SLC-5/05In many cases the best solution is to simply upgrade to a SLC-5/05 with built-in Ethernet. The main down of this solution is the cost of this new processor.

If you’re upgrading from a 5/01, 5/02, or 5/03 on which the DH-485 port is actively being used, you can add a 1761-NET-AIC and associated cable to the serial port of the SLC-5/05 in order to maintain DH-485 communications.

If you’re upgrading from a SLC-5/03 or SLC-5/04 on which only the serial port is in use, you can use the serial port on the SLC-5/05 in it’s place.

However, if your SLC-5/03 is using both ports, or your 5/04 is using it’s DH+ port, the 5/05’s single serial port won’t be able to replicate those configurations, and you may want to consider one of the other options below.

Channel 0 Serial to Ethernet with the 1761-NET-ENI

1761-NET-ENIIf you have a SLC-5/03 or 5/04 on which the serial port is available, you can add a 1761-NET-ENI Serial to Ethernet converter.

While the ENI doesn’t support the same number of “connections” and “packets per second” as the SLC-5/05, it’s fairly simple to add and configure.

However, I would suggest comparing the ENI’s price to the other options as its price has risen over the years.

DH-485 bridging to Ethernet with a Prosoft Gateway

Prosoft 5201If you have a network of SLC-500’s and other devices on DH-485, you can bridge that network to Ethernet with the Prosoft 5201-DFNT-DH485 gateway.

The down side is, this device is in the end of its lifecycle and will only be available for a limited time.

DH+ bridging to Ethernet with a Prosoft Gateway

AN-X2-AB-DHRIOIf you have a SLC-5/04 using channel 1, or a network of DH+ devices you want to bridge to Ethernet, the Prosoft AN-X2-AB-DHRIO gateway is a modern, easy to setup, bridge between DH+ and Ethernet which emulates a ControlLogix gateway.

Bridging a DH+ or DH-485 network to Ethernet with a ControlLogix Gateway

DH-485 ControlLogix GatewayIf you have multiple SLC-500’s and other devices on a DH-485 or DH+ network, one option to bridge those to Ethernet is to install a ControlLogix Gateway.

This solution consists of a 1756 power supply, chassis, Ethernet card, and either a 1756-DHRIO, or 1756-DH485 module with a 1761-NET-AIC.

Prosoft 1746 Ethernet Module

Prosoft MVI46-DFNTThe last item on the list is the Prosoft MVI46-DFNT Ethernet Module.

This single slot 1746 module uses M files and ladder logic to act as either an Ethernet messaging server or client.

This module also has an “Ethernet to Serial” pass-through capability which acts much like the 1761-NET-ENI, and allows remote monitoring and editing of the SLC-500 using RSLogix 500.

I hope the above information about adding Ethernet to a SLC-500 is helpful. If you have any comments, questions, suggestions or corrections, please leave them with us by using the “leave a reply” form at the bottom of this page


Shawn Tierney
Automation Blogger and Trainer

Need personalized help? For as little as $25 per month you can get direct access to ask me Rockwell PLC, HMI, and SCADA questions! Learn the details at

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