ControlLogix 5555 Serial Comm. Method to DeltaV (DCS)

ebolbol · Aug 16, 2017

The only thing I've ever used a Logix controller serial port is for configuration purposes. I have never seen that port utilized for data transmission to other control systems (Until Now).

There appears to be a comm. setup between a L55 and Emerson DeltaV system. I'm very familiar with RS-232, 485 & MODBUS protocols.

Would one of you ladies or gentlemen describe to me how this would be configured and achieved in 5 yr old terminology?

Ron Beaufort · Aug 16, 2017

not sure if this is what you're asking for - but see if this will help get you started ... if not, give us some more details of what piece of the puzzle you're having issues with - and we'll try again ...

.

Ken Roach · Aug 16, 2017

Is this a Mynah interface on an Emergson programmable serial interface module ?

https://www.mynah.com/product/deltav-serial-drivers

There is a long history of these modules and their firmware, and not all of it has been happy. Hopefully it's using ordinary DF1 Full Duplex.

The most common problem I've had with such a connection is that the Mynah/Emerson firmware inter-poll delays were not fully implemented, so the serial module would swamp the controller with requests for data, starving the controller's resources to do other tasks. Or, the error codes weren't well understood, so a loose serial cable between modules turned into a bitter finger-pointing exercise.

ebolbol · Aug 16, 2017

Ron Beaufort said:
not sure if this is what you're asking for - but see if this will help get you started ... if not, give us some more details of what piece of the puzzle you're having issues with - and we'll try again ...

.

Ken Roach said:
Is this a Mynah interface on an Emergson programmable serial interface module ?

https://www.mynah.com/product/deltav-serial-drivers

There is a long history of these modules and their firmware, and not all of it has been happy. Hopefully it's using ordinary DF1 Full Duplex.

The most common problem I've had with such a connection is that the Mynah/Emerson firmware inter-poll delays were not fully implemented, so the serial module would swamp the controller with requests for data, starving the controller's resources to do other tasks. Or, the error codes weren't well understood, so a loose serial cable between modules turned into a bitter finger-pointing exercise.

Ron, I just wanted to understand how another system would poll the L55 for data. Is the setup you have attached all it takes? How do the systems know when to talk how long to talk and what data to collect?

Ken, Not a clue what that is but I can look into it.

I just wanted to understand how L55 controller shares data with another system through this port without some kind of Master/Slave convention

Ken Roach · Aug 16, 2017

It's a basic peer/peer or request/respond function.

For the early generations, the Mynah serial interface treated the ControlLogix like an SLC-500 integer data table. It would send data table read and data table write commands with addressing representing the classic "N7:0" style Allen-Bradley data tables, and the ControlLogix would respond with the contents of the Array Tags that are associated with those data tables in the "PLC/SLC Mapping" feature.

This is very similar to a device emulating a Modbus holding register table. The addressing and command codes are just a little more complicated with Allen-Bradley DF1 than they are with Modbus.

I mentioned "N7:0" above; the ordinary 32-bit single-precision floating point "F8:0" data tables were also implemented.

Modern Mynah modules might use ControlLogix native tag addressing instead of SLC/PLC data table emulation. I'm not sure.

In general, the ControlLogix was a passive device; it only responds to the Myah/DeltaV serial module's commands. You don't have to put in MSG instructions or anything but the emulated data table configuration in order to make it work on the A-B side.

Mynah "virtual IO module" configurations inside the DeltaV configuration environment are outside of my scope of experience.

ebolbol · Aug 16, 2017

Ken Roach said:
It's a basic peer/peer or request/respond function.

For the early generations, the Mynah serial interface treated the ControlLogix like an SLC-500 integer data table. It would send data table read and data table write commands with addressing representing the classic "N7:0" style Allen-Bradley data tables, and the ControlLogix would respond with the contents of the Array Tags that are associated with those data tables in the "PLC/SLC Mapping" feature.

This is very similar to a device emulating a Modbus holding register table. The addressing and command codes are just a little more complicated with Allen-Bradley DF1 than they are with Modbus.

I mentioned "N7:0" above; the ordinary 32-bit single-precision floating point "F8:0" data tables were also implemented.

Modern Mynah modules might use ControlLogix native tag addressing instead of SLC/PLC data table emulation. I'm not sure.

In general, the ControlLogix was a passive device; it only responds to the Myah/DeltaV serial module's commands. You don't have to put in MSG instructions or anything but the emulated data table configuration in order to make it work on the A-B side.

Mynah "virtual IO module" configurations inside the DeltaV configuration environment are outside of my scope of experience.

Thank you Ken. That makes it a little more clear. Appreciated as always.

ControlLogix 5555 Serial Comm. Method to DeltaV (DCS)

ebolbol

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Ron Beaufort

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Ken Roach

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ebolbol

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Ken Roach

Lifetime Supporting Member + Moderator

ebolbol

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