Data Highway Interface

We have a customer who has a PLC5/25 controller that uses interfaces to a Fischer-Provox system using a 1785-KA on the PLC5 end and a 1771-KX1 on the Provox end. Legacy Data Highway connects the two modules.

The are replacing the PLC5 with a CompactLogix system but are wanting to keep use their existing Provox PCIU. I was wanting to convert the Data Highway to something the CompactLogix could use such as DF1 or DH485 (rs232). Was also planning on using the same addressing in the PLC5 using the PLC5 mapping function in the Logix.

Any ideas on what equipment to make this happen?

Thanks!

I can almost guarantee the mapping function will not work. I cant get it to work between SLC and Logix PLC's. The 1771-KX1 is Datahighway and not Datahighway Plus which means there is no way for the Logix to communicate on it. You may have to leave the PLC5 in place and just use it as a information gateway. You would need a 1756-DHRIO card to communicate over Datahighway Plus to the PLC5. That would keep it going until you can find a way to eliminate/upgrade the Fischer system.

Planning a CompactLogix in a legacy process control application always sets of alarm bells with me, if only for maintenance spares reasons.

You may be able to use the existing hardware with a 1756-DHRIO; despite my colleague's objections, I have used the SLC/PLC Mapping feature successfully and extensively for many years, though not with a PLC-2 style data command passing through two 1980's-vintage network modules.

Another option would be to get a vintage 1770-KF2, since those are the only device I'm aware of that supports either Data Highway or Data Highway Plus on the network side. Of course then you'd need a serial port on your Logix-family controller, and none of the modern CompactLogix have one.

1756 series hardware and the 1756-DHRIO are my recommendation.

If I remember correctly that PCIU always uses the PLC-2 format. At least that's how it was the last time I did one of those 25 years ago.

The old SST 5136-SD supports both DH and DH+. We have a couple laying around the lab, or you can find them on the used/resale market. You could build a gateway using a SoftPLC with a slot to accept the SST card. It supports the PLC-2 compatibility mode to talk to the Fischer system, and provides PLC-5 style addresses on the other side to connect either serially or via ethernet.