SLC500 5/05 DF1 serial communications with Honeywell HPM SI module

Has anybody had any luck successfully achieving a serial comms connection (RS232 DF1) between the Ch0 port of an Allen Bradley SLC500 5/05 CPU and a Honeywell HPM Serial Interface (SI) module with A/B interface FTA module (P/N: MU-TSIA12)? All comms settings have been checked at both ends, vendor documentation has been followed, cable pin-outs verified, all without success. Any suggestions would be greatly appreciated. Cheers

Welcome to the Forum !

I haven't used this specific DCS interface, but in my general experience you need both written documentation and careful electrical and protocol analysis to get one of these old DCS interfaces to work.

The documentation I see for that device says it's built for PLC-2, 3, and 5 controller interfaces. Remember that those have DB25 connectors, for which the pin assignments are different from the DB9 connectors on an SLC-5/0x controller.

Do you know which exact PCCC command code the SI module is using ?

It's possible the DCS is using the old PLC-2 command set. In the SLC controller, only Data File 9 can be accessed with the PLC-2 command set, aka the "Common Interface File" or "CIF".

The last time I did a DCS serial interface, I used the USB/RS232 intercept box from Frontline Test Equipment, along with their NetDecoder software. There's no doubt those tools made the difference between success and failure.

The quick and dirty way to see what the DCS is doing is to hook up the serial cable to your PC instead of the SLC-5/05 controller, and use a serial sniffer or terminal program to see what hex bytes are being sent by the DCS.

Thanks for your help in pointing us in the right direction and sharing your experience on this topic. Turns out (based on some feedback we received from Honeywell today and some A/B documentation I found) that you are right on the money with your comments.

The A/B DCS serial interface seems to use PCCC command codes that will only work in PLC-5, such as 'Word Range Read' (which happens to be the command we need the most in this application). An equivalent and supposedly more robust command (according to A/B document 'PLC-5 and SLC-5/04 Communication Driver Comparison') 'Typed Read' is understood by both PLC-5 and SLC-5/04, but unfortunately our DCS interface doesn't use that command.

The Honeywell knowledge base is steering us in the direction of using an A/B Communication Interface like a 1770-KF3 or equivalent to achieve a serial link. So tomorrow we'll try a 1761-NET-AIC, even though we were hoping to simplify this system by getting rid of such devices and utilising a single direct RS232 link between the PLC and DCS.
Cheers

I found an old copy of that "PLC-5 and SLC-5/04 Communication Driver Comparison" on the IATIPS website.... it's dated 1995 !

Word Range Read and Word Range Write are DF1 Command 0x0F with Function 0x00 and 0x01.

Pages 7-2 and 7-3 of the DF1 Protocol Reference Manual (Publication 1770-RM516) have a great summary table that includes most of the DF1 command supported by a wide variety of A-B PLC/SLC controllers.

The 1761-NET-AIC won't do anything useful; it's just an RS-485 to RS-232 electrical converter and isolator. In combination with a 1770-KF3... (ancient, obsolete...) I'd have to dig out a bunch of manuals. It would be ugly.

If I were building the system, I would use a Prosoft MVI46-DFCM module.

I know that they support the PLC-5 Word Range Read and Write commands. I have used the MVI56 version of these modules to interface with a Fisher Provox Serial Interface module successfully.

For me, knowing that the DCS can only read and write into a coprocessor style module is a reassuring thing; there's absolutely no question about where the data is coming from and a minimum of finger-pointing when the interface doesn't work. The debug port on the MVI module has been a very valuable tool for me as well.