Messaging a PLC 2 over a 1756 DHRIO connection with an L81E

I have been doing some research on data highway and data highway plus, and have contacted Allen Bradley for information regarding communication. We are currently working on a project that involves us upgrading a clients PLC from a PLC 5 to an L81E processor, I have run into an issue where the old programs destination node is larger then 77 which wont be accepted into a new message instruction. I believe this to be addressing a DH connection that I read has a different node addressing system. The customer would like to keep the same network so we were considering using a 1756 DHRIO card to communicate on the DH+ network. Has anyone had experience in this and can steer me in the right direction. Thanks

EquipmentAsOldAsMe said:

View attachment 51247I have been doing some research on data highway and data highway plus, and have contacted Allen Bradley for information regarding communication. We are currently working on a project that involves us upgrading a clients PLC from a PLC 5 to an L81E processor, I have run into an issue where the old programs destination node is larger then 77 which wont be accepted into a new message instruction. I believe this to be addressing a DH connection that I read has a different node addressing system. The customer would like to keep the same network so we were considering using a 1756 DHRIO card to communicate on the DH+ network. Has anyone had experience in this and can steer me in the right direction. Thanks

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Welcome to the forum!

It's been a while ... Data Highway was never one of my strong suits.

The station addresses in Data Highway were octal. But I think that the address listing doesn't preface the number is O or 0 to indicate that.

On an unrelated note - you're actually using a PLC-2 on Data Highway ... and the PLC that you are replacing is the PLC-5? You have not been able to repair PLC-2 through Allen-Bradley/Rockwell for a long time now. I guess they could be using one of the 2 or 3 electronics shops left that will fix PLC-2 cards .. with antique stock ...

I would suggest that this system needs an upgrade that has a larger scope than you have.

Sorry I can't help with the problem. I have no operational software for PLC-2, and the 1784-KT card that I still have only works with an ISA computer ... my last Pentium 500 died a couple of years ago

I think I have one operational 1771-KF that will talk Data Highway ... that I have not recycled yet (LOL)

The PLC-5 was probably using a DH+ to DH bridge to communicate with the old PLC-2 on Data Highway. It's probably a 1785-KA.

That's consistent with the Remote Link addressing. The DH+ message contains a flag indicating "this is a message for a remote network", and the bridge device passes the message to the appropriate "Link" (essentially a subnet) and the appropriate Station on that Data Highway network.

The 1756-DHRIO doesn't support the old Data Highway as a Remote Link Type, just DH+, so it limits the Node Numbers and Link Numbers to the DH+ maximum of 77 (octal).

I don't think you can use a DHRIO and a 1785-KA together; the DHRIO just doesn't have the ability to handle those old bridged network messages.

This issue may be the predicate for updating the PLC-2 controller, or fitting it with a native DH+ interface like a 1785-KA3.

Have a look or Ring Prosoft, they had some DH+ to Ethernet adaptors ( i purchased one long ago and it still works on my PLC 5 DH+ network)
so maybe they did a Data Highway version ?

If there is a DF-1 port available on the PLC-2 you could use this device. It's very easy to setup, doesn't require any PLC programming (as long as the data files/tags already exist) and doesn't require any programming software (it's web based).
https://www.spectrumcontrols.com/products/webport-solutions/universal-gateway/

Firejo said:

If there is a DF-1 port available on the PLC-2 you could use this device. It's very easy to setup, doesn't require any PLC programming (as long as the data files/tags already exist) and doesn't require any programming software (it's web based).
https://www.spectrumcontrols.com/products/webport-solutions/universal-gateway/

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I don't recall any PLC2 with DF1 ports.
Same for first "Classic" generation of PLC5

There's so little Data Highway left in the world, I don't think you will find an Ethernet to Data Highway interface. I'm certainly willing to be incorrect, but if you do find one, ask the vendor about the differences between DH+ and DH until you're confident they understand the question.

The PLC-2 front port is not an ordinary DF1 RS-232 (or even 232/422/485 like the PLC5 Enhanced controllers) port; I think it's a current loop serial port, and the only devices I've ever seen connect directly to it are PLC-2 specific things like the SmartCable and PCMK cable and the ports on a 1785-KA or 1785-KA3 or 1771-KG.

Does the Spectrum Universal Gateway support PLC-2 common interface file message types on DF1 ? I will be impressed if it does.

The old 1770-KF2 serial to DH/DH+ (it did support both !) interface might also have a role, depending on what data needs to be retrieved from that PLC-2 and the architecture of the overall control system. The KF2 doesn't support off-link messaging so it would have to be connected directly to the DH (not the DH+) network.

As long as we're rummaging through the eBay bin, the 1771-KG was a PLC-2 front port to RS-232 interface, if you can find one.

If a DF1 gateway (like the Spectrum unit) can connect to the RS-232 port of a KF2 or KG module, then it might functionally create an EtherNet/IP to Data Highway connection.

Ken Roach said:

Does the Spectrum Universal Gateway support PLC-2 common interface file message types on DF1 ? I will be impressed if it does.

Click to expand...

The only testing I've done in the "PLC-X" family is a PLC-5 so I don't know if it will work with a PLC-2. I know so little about them (I've never seen one in person). I wasn't sure if they had a DF-1 port or not. I read a few blog posts that talked about DF-1 and PLC-2 but there wasn't enough info to say one way or the other.
Kinda shot in the dark although one of the first applications tested was with a PLC-5 and a ControlLogix (which is what I tested).

Many devices that implement DF1 start with the "Common Interface File" commands. PLC-2 controllers had a flat memory structure, instead of having different "data table types" like a PLC-5 has (In, Out, Binary, Timer, Counter iNteger, etc).

Even the ControlLogix has retained this CIF file feature, allowing you to send and receive PLC-2 style messages or the equivalent CIF file in very old SLC-500 controllers.

But when we get back into the leading-edge technology of 1978, there's going to be some things that just don't work simply.

Thanks everyone has given some good direction. We are checking to see if the communications are over a remote bridge to DF1 rather just a DH remote. The ControlLogix Data
Highway
Plus-Remote I/O
Communication
Interface Module manual
https://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um514_-en-p.pdf
Shows that the Path in the msg instruction can communicate to a DF1 connection. Has anyone successfully done this and provide an example? Thanks, in this scenario we cant upgrade the Legacy equipment until next year and we need a band aid solution until they can replace the equipment.

A MSG instruction can use the serial port of a ControlLogix, even if that ControlLogix is not the source of the MSG.

But of course the last two generations of ControlLogix CPUs don't have RS-232 ports; you have to go back to the 1756-L6x (or L55x or L1) to get a serial port.

I agree that you need to get details on the network connection. I've done a good amount of legacy PLC networking and have been burned by surveys by others that describe equipment that's been removed, modified, customized, or misunderstood.