Communicating from DH+ to DH+ networks


Thread Starter

Jett, Darin

I have 2 separate DH+ networks in my plant. I would like to be able to send a couple of status bits from one PLC on the east network to an RSView
station on the west network for alarming.

We have 3 computers with dual channel KTX cards connected to both networks. Can I use one of these logging computers with RSLinx (not Lite) to pass the information through?

Darin Jett
If you are using RSLinx in its OPC configuration you can use a package from Iconics called Dataworx it is used to pass data in a high speed method between OPC servers and has options for redundancy if you need it and it is critical data.

Mark Massa
You've put your finger on one of the features that WinLinx Gateway had which RSLinx Gateway does not; DH+ to DH+ bridging. WinLinx Gateway (for 16-bit Win31 and Win95 systems) could conduct unsolicited messages from PLC's between DH+ channels on 1784-KTX and 1784-KTXD cards. This didn't support remote programming; that was too much traffic and RSLinx and AI clients never had the routing enabled, in order to prevent this function from being attempted. RSLinx Gateway excels at routing TCP/IP packets from other RSLinx clients onto A-B networks (DH485, DH+, ControlNet, etc), but it can't route between DH+ networks.

For this application, use a 1756-DHRIO ControlLogix Gateway module. You'll need a power supply, chassis, and the 1756-GTWY software ($150) to set up the routing tables. I recommend this instead of a pair of 1785-KA
modules; it's simpler to configure and understand.


Ken Roach
A-B Seattle

Anthony de la Rosa

you should just join the two networks together if the total length is under 10,000 ft. You can send data using the MSG message instruction. The MSG instruction can pass up to 100 words per packet.

I have too much communications going on for that. That's why I split the network in 2 last year. 23 nodes, 12 of which are SLC5/04's, 3 RSView stations, 2 logging computers on both networks, laptop, Quickpanel, plus my desktop on both networks.

I think what I'm going to do is have one of our guys write up a FoxPro app which reads a byte in the source SLC and on a change writes it to the source SLC. This can run on one of the logging computers which has a KTX(D) on both networks.

Vitor Finkel


If you really mean "a couple" of status bits, may I suggest the time proven Low-Tech solution of wiring 2 wire pairs between discrete output modules of one PLC, and Input modules of a PLC residing in the other network ?

For a very small quantity of signals, this is probably a low cost and reliable solution. Programming coudn't be easier, "configuration
and understandability" couldn't be simpler.

Vitor Finkel [email protected]
P.O. Box 16061 tel (+55) 21 285-5641
22222.970 Rio de Janeiro Brazil fax (+55) 21 205-3339

Lynn August Linse

Couldn't you link the DF1 serial ports of 2 PLC by a fiber optic or short-haul modems or a pair of Ethernet/RS-232 servers & use some form of
MSG block in/out the serial port? This wouldn't work if the PLC somehow tries to "merge" the active DF1 port into the DH+ address space, but if you could just make it into 2 nodes on a point-to-point link it should work.


Lynn August Linse, Senior Product Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected]
Tel: (949)450-7272 Fax: (949)453-7132
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