SLC-5/03 DH-485 messaging through multiple Ethernet Gateways?

Here's my situation:

Multiple SLC-5/03 that share data via messaging over DH-485.
The client wants to get rid of the DH-485 network and go to Ethernet
The client wants to replace with SLC-5/05; to me, this is not a good long-term solution. I'd prefer to suggest using gateways.

The question is this:

Is it possible using a DH-485 to EthernetI/P gateway at each SLC, and somehow still do the SLC-to-SLC messaging through the DH-485 ports (via the gateways)?


So we'd have this:

SLC - gateway - Ethernet - gateway - SLC

passing messages as normal. The obstacle I see is that the SLC is looking for a DH-485 station address. Is there any way to configure the gateways to know what station address they are mimicing?

Joe@ICA said:

The client wants to get rid of the DH-485 network and go to Ethernet
The client wants to replace with SLC-5/05; to me, this is not a good long-term solution. I'd prefer to suggest using gateways.

The question is this:

Is it possible using a DH-485 to EthernetI/P gateway at each SLC, and somehow still do the SLC-to-SLC messaging through the DH-485 ports (via the gateways)?


So we'd have this:

SLC - gateway - Ethernet - gateway - SLC

passing messages as normal. The obstacle I see is that the SLC is looking for a DH-485 station address. Is there any way to configure the gateways to know what station address they are mimicing?

Click to expand...

I agree with the customer. Plug in some 5/05s and have ethernet for peer to peer communication. The reasons are not limited to the future of trying to maintain a DH485 network and associated adapters, but I suspect the 5/05 to be around longer than the 5/03, certainly at least as long.

Also, DH485 bottlenecks you at 19.2k, The only way past that is to lose the 5/03 unless you go DF1 at 38.4k over ethernet with Digi modules or Net-Eni gateways.

Lose the DH485 network, or you have not made a real upgrade, in my opinion.

Then, phase II, you get a Logix controller involver, plug in a 1747-AENTR to hte existing ethernet cable where your 5/05 was connected, and keep the 1746 I/O.

I actually tend to agree with your client's approach; Upgrading to SLC-5/05 controllers gives you greatly increased communications speed and capacity.

There are a very small number of devices on the market that could be considered a DH485 to Ethernet gateway; you're probably thinking of the DataLink GW1000 device:

http://www.datatechgateways.com/gw-1000-abeip-dh-485/

I am usually hesitant to give advice on a device I have no direct experience with, but based on what I've read it will not do what you want.

The GW1000 devices are intended to allow devices on an Ethernet network to initiate messages to devices on a DH485 network. I can't see anything on the website or in the user manual that suggests they'll allow messaging to be initiated in the opposite direction.

If you look at the MSG instruction in the SLC-5/03, you'll see that it's fixed at "Local" mode. There isn't a Bridge and Link address that could be used to navigate through a network outside the 31 nodes of the local DH485.

I could be making assumptions that aren't true in your case. What exact gateway devices are you interested in using ?

The 5/05s just seem a waste of money. If I can do this with a gateway, then they'll be in a position to do the upgrade to ControlLogix sooner. I'm not concerned about the baud rate limitation; they've been running with this for ages.

I wanted them to go with the ControlLogix processor and the 1747-AENTR, but they are't prepared to spend money on converting the program. They know we can use the conversion utility, but they prefer not to do that at this time.


So back to my original question: is there any way to do what I'm trying to do?

Ken Roach said:

I actually tend to agree with your client's approach; Upgrading to SLC-5/05 controllers gives you greatly increased communications speed and capacity.?

Click to expand...

They don't really need it. And these systems will be replaced AGAIN inside of 2 years anyway.

Ken Roach said:

There are a very small number of devices on the market that could be considered a DH485 to Ethernet gateway; you're probably thinking of the DataLink GW1000 device:

?

Click to expand...

That's one of the ones I was looking at.

Ken Roach said:

If you look at the MSG instruction in the SLC-5/03, you'll see that it's fixed at "Local" mode. There isn't a Bridge and Link address that could be used to navigate through a network outside the 31 nodes of the local DH485.

Click to expand...

What's I'm hoping is that one of the gateways will be able to mimic the SLC and forward the messages. I saw one from Prosoft that MIGHT do what I want, but they're closed today, so I'll have to wait until Monday to call

Yes, I believe that a Logix 1756 chassis can be a nice bridge with a 1756-EN2T or ENBT and a 1756-DH485 card. Then you're just adding a physical node to the DH485 CPU so you don't need a separate module other than what you already have plugged into the SLC already.

-Power supply
-756 four slot rack
two cards:
-1756-ENxT
-1756-DH485
-some DH485 wiring
-cat5 wiring
-good quality ethernet switch.

One bridge, up to a dozen or so nodes with good throughput.

http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1756-in587_-en-p.pdf

Why does the customer want to "go Ethernet" in the first place, if they don't need additional speed or capacity ?

If you're going to stick with the DH-485 port of an SLC-5/03, look at the configuration of the MSG instruction.

There's no "Remote" mode. There's no "Gateway Address", no "Link Number", and no "Remote Address".

DH, DH-II, and DH+ have some or all of these features. DH-485 has none of them.

That's why I don't think there is any way to send a MSG instruction from an SLC-5/03 controller's DH485 port to a "gateway", then across Ethernet to another "gateway", then to the DH485 port of another SLC-5/03.

This sort of message routing is possible with Channel 0 and the DF1 protocol using the 1761-NET-ENI and the Destination Mapping feature. Unfortunately the 50 possible Destination Map entries is a lot more than the six possible outgoing TCP connections, so for your multiple-controller system it might not be practical.

This http://www.prosoft-technology.com/p...ip/dh_485_to_ethernet_ip_communication_module will do what you need but they ain't cheap.

For the cost I agree with the customer just go with 5/05 processors. maybe it is a wste but it's their money. Keep this in mind any time you add additional components to any system you add points of possible failure and additional complexity.

If a gateway was you only method or your customer insisted on a gateway then that would be another story but they want to do it the right way and it is beneficial to do that for their sake and yours. I don't know your experience but I have had a ton of experience in setting up varios gateways such as this and I have to have one go smooth yet. You normally fight them all the way.

If your customer has issues with this gateway solution after they wanted 5/05 it will look very bad on you. keep that in mind also.

Take my advice go with the 5/05 and you and your customer will be happier.

While the Prosoft module will allow you to get data from one SLC to another, it's not going it by "proxying" or "passing" the DH485 commands across an Ethernet link. It's doing it by using Command Lists and/or the classic Prosoft 5000-word shared data file.

If I were being asked to do this system, I would have to sit down and diagram the data exchange from one SLC-5/03 to another, then have a meaningful discussion with the customer about what features and benefits they want to get from "going Ethernet".