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.

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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 “post a comment or question” link below


Shawn Tierney
Automation Instructor and Blogger (post views: 11,038 views)

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Forum Comments:
  1. Good day Shawn.
    We are replacing a PLC5/40E with BASIC card to a serial printer, RIO modules for IO, and a DH+ HMI, and Ethernet for data collection, with a SLC system.
    I wanted to use a SLC-5/05 to get Ethernet, but would lose the HMI connection, and cannot find a reasonably priced Ethernet to DH+ solution.
    To maintain the existing HMI, I can use a 5/04 - giving me its serial port for the printer, and its DH+ for the HMI - add a RIO scanner card, for the IO. But now I lose the data collection requirement. Unfortunately, since its RS232 port is going to be used for the printer, a NET-ENI is not an option.
    Any ideas?
    Good morning ,
    Sounds like you need RS232 Serial for the Printer, Ethernet for data, and DH+ for the HMI, but as you said an SLC doesn't come with all three, and the ENI is out because you have to have the serial port 🙁
    - Question: Does the HMI have another communications port?
    Many people have PVPlus HMI's and don't realize how easy it is to change them from DH+ to Ethernet or DF1. However if you have a legacy HMI with only DH+ you'll likely need to stay with the 5/04 unless you have the budget to update it to a PVPlus 7 (there are some lower cost options which allow you to import legacy PV projects.)
    - DH+ to Ethernet options
    There are quite a few options in this area under $2K including the Prosoft and Automation Networks. While these may seem pricey, the could be less expensive then upgrading an HMI, writing Basic code, or even buying the now expensive ENIs:
    - Serial
    Finally, you could use the old ENI on the serial port and use a 1746-BAS module with similar code that you had in your 1771-BAS module. As far as strict 1746 ASCII modules it looks like the ones I'm familiar with are obsolete.
    I also haven't tried a SLC Ethernet MSG to ASCII output device, but you may want to check out this article to see if the device he used would work with a SLC:
    Another option may be to use a 1747-DPS1 Port Splitter Port splitter on a SLC-5/05 channel 0 with ASCII on one port and the ENI on the other. Check out the information below to see if it would work in your app:
    Hope this helps!
    Shawn Tierney, The Automation Blog

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