A question has come up...interfacing a PLC-5 processor with Omron's new Ethernet/IP card. I just wrapped up one of Omron's first application in the US of their new CS1W-EIP21 Ethernet/IP card so that end I have covered. But I have not done an Ethernet application on a PLC-5 - ever. CompactLogix and ControlLogix are very different animals than the PLC-5.

Does any of you on the forum have experience with PLC-5 for Ethernet applications? I am curious as to how to setup the tag structure. I imagine one must define tags (Data File) for the Ethernet/IP card to read/write from/to.

I downloaded some of the PLC-5 EDS files from Allen-Bradley's web site, but have not gotten any to work (Omron does not recognize the parameters of the files).

SLCs are very similar, programming end, to the PLC-5, and I have worked on many SLC Ethernet projects. But all of those were with devices that easily adapted to the programming of a SLC. The Omron card deals with interfacing on a more higher-level Ethernet/IP scheme (produced and consumed tags). If anyone has setup produced and consumed tags between a PLC-5 and a Compact or ControlLogix, then I think the Omron interface can be pulled off.

This might not be workable.

In my understanding, the PLC-5's implementation of EtherNet/IP is strictly an implementation of the PCCC protocol using an EtherNet/IP connection and transport set. A PLC-5 can send PLC and SLC addressed reads and writes to PLC and SLC and Logix processors.

But a PLC-5 cannot directly read or write a Logix tag; addressing is always translated using the Data File Mapping feature.

The PLC-5 does not support Produced/Consumed data exchange of EtherNet/IP, and it does not support EtherNet/IP I/O connections.

I know that the MicroLogix 1100 can perform a CIP Generic service, and the SLC-5/05 might be able to as well, but as far as I know the PLC-5 cannot.

It's been a while since I examined closely the Ethernet feature set of the PLC-5; I'd be happy to learn that I'm behind the times.

Short answer: You are NEVER going to get this to work directly. You stand a much better chance of getting everything to work over Modbus (RS-485), DF-1 (serial or other flavor), or Modbus/TCP.

PLC-5's can use explicit messaging only. And they use PCCC. SLC's are the same but they can use CSP (but I don't think they can use CIP). Micrologix does CIP or CSP but not PCCC. PLC-5's and SLC's that can communicate via "Ethernet/IP" are encapsulating PCCC (DF-1) packets inside CIP packets using a "vendor specific protocol" within the CIP protocol...in other words, loading the older protocol as a payload embedded inside CIP. Since the tag format of a CLX processor is so alien to SLC/PLC-5, the "translation tool" maps CLX tag names into the older SLC/PLC-5 tag name space. This is similar to the special mapping that is done even on SLC/PLC-5 to communicate successfully to PLC-3....it's a backwards compatibility feature.

PLC-5's (and SLC's) CANNOT do producer/consumer messaging, aka "unsolicited" messages. In this mode, at a protocol level, the receiver (consumer) specifies what data it expects to receive and the transmitter (producer) automatically generates the packets at the required rate (RPI).

Even IO on PLC-5's and SLC's is "passive". On a RIO network, there is always exactly one "scanner". All IO sits passively. The scanner polls all the IO in turn. It's very convenient and for the most part automatic on a SLC or PLC-5 so you don't have to worry about the details (at least for digital IO), but the requirement that the processor still does all the polling exists.

For this reason, PLC-5's and SLC's simply CANNOT, WILL NOT, do Ethernet/IP based IO. And unless the Omron implements the special backwards compatibility CSP/PCCC packets over CIP mode, you stand 0.0% chance of EVER making it talk directly to a PLC-5 or a SLC, or probably even a Micrologix for that matter.

If you want to still make this work, here are your options:
1. Insert a CLX processor such as the cheapest CompactLogix or similar that AB makes into the system. You're not going to use it as a CPU. Just set up the translation mapping tool and create some tags. This allows the Omron and PLC-5/SLC hardware to freely read/write the data tables as needed.
2. Use Modbus. Either write serial code on one or both sides to talk using Modbus or buy something like a Digi One IAP or several other equivalent products to act as a protocol bridge.
3. Use Modbus/TCP. For the PLC-5, you HAVE to have a protocol bridge.
4. Use DF-1. Native to the PLC-5 but you will need a protocol bridge (or code) this time on the Omron side.
5. Use discrete or analog IO's (inputs tied to outputs). Ugly but 100% compatibility at the electrical level and frequently faster than any other option, especially if you're not pushing large amounts of data.

Final suggestion: just as with every other plant, start making plans to upgrade those old PLC-5's and SLC's to a CLX processor in the future.

Thank you very much, Paul and Ken. My experience tells me that integrating anything Ethernet/IP with a PLC-5 will not be an easy chore. The suggestion of using a CompactLogix as a Gateway is probably the best solution. I have no details of the full application, as the question was posed as a conceptual one. There are a lot of PLC-5 racks in use out there, with their full replacement not having much financial merit. A Gateway approach keeps the integration simple and lower-cost (less programming covers most hardware costs).

Thank you.