SLC500 com with PCMK

Is an adapter cable available to interface
an AB-PCMK (DH+) to a SLC500 RJ11 com port (fixed I/O controller)?

From everything I see at AB.COM the SLC500
fixed controllers only go DH-485 (1747-PIC).

The 1784-PCMK card actually supports several different protocols; DH+, DH-485, RIO, and PLC-2 "PCL".

It's best known and mostly used for DH+, as you observed.

You can get a cable that will allow the 1784-PCMK to connect directly to the RJ-45 style DH-485 network port on a fixed SLC-500. The part number is 1784-PCM4.

The PCMK Series A and Series B cards have different connectors, so make sure you know your Series letter and get the Series A or B cable to match.