PLC3 DF1 to ControlLogix Gateway

We are replacing a PLC3 with a new ControlLogix. There is an existing mainframe application that communicates with the PLC3 via a 1770-KF2 (DF1 RS-232 Full-duplex on the mainframe side, DH+ on the PLC3 side).

We purchased a ProLinx Ethernet to DF1 Gateway to convert the mainframe DF1 connection over to Ethernet for the ControlLogix. The Gateway appears to the DF1 network as a SLC 5/04 PLC and to the ControlLogix as an Ethernet/IP device.

Even though PLC3 and SLC use the same address naming conventions (N7:0, etc) we discovered that the PLC3 DF1 protocol uses CMD/FNC codes that are not recognized by the SLC 5/04 processor that the gateway is emulating.

Are there any gateway products that support PLC3 DF1 commands and can communicate with a ContolLogix either via Ethernet/IP or DH+? Reprogramming the mainframe application is not something we currently have the resources to tackle.

Do you have the details of precisely which CMD and FNC codes the mainframe application is using ? The issue is probably with the symbolic encoding of the address, rather than the actual command or function.

When I was investigating a similar migration about five years ago, I stepped in a similar trap; when I read that the device supported "the complete DF1 command set" I didn't look closely enough at the supported commands and addressing formats.

At the time, I found nothing that supported those specific PLC-3 address modes.

Similar PLC-3 upgrades got lucky and it turned out that the DCS system was using PLC-2 style unprotected reads and writes (CMD 01 and CMD 08), and I was able to use a Prosoft MVI56-DFNT module.

Look also at the Miille Applied Research communication modules; Jerry Miille has been doing A-B comms for a very long time and if anyone can get a device like the Omni-Comm to speak PLC-3 style addresses, he can.