Emerson Exchange 365

External Reference to DST reference or use DI block?

I'm converting an obsolete MTL8000 multiplexor to DeltaV remote I/O (M-series). The cards are almost entirely discrete inputs (motor run statuses / "M" contact).

The existing modules were designed with "external references" to DI blocks that brought in the MTL8000 I/O via RS485 / Modbus RTU. The only DST was the the serial "datasets" which brought in the discrete I/O as one "read" of the Modbus registers.

To simplify the cutover, I want to just use the DST in place of the external reference to the DI block. We're aiming to do one rack of eight cards in a day while the plant is running. The new I/O is connected to the DeltaV system so we can commission the RIO processors and assign the appropriate DST to each channel.

Am I correct to presume that the DST value will be a "1" or a "0" just like the external reference to the DI block (which pointed to the modbus register). The original design did not do any signal conditioning or alarming in the DI block . . . I think the original systems engineer thought he needed them (the DI blocks) to pass the Modbus I/O to DeltaV modules. Who knows maybe you did in version 4.

I was thinking I could just bulk edit the modules and change the external references to point to the DST (both INPUT_1 and INPUT_2 pointing to the same DST) for the corresponding RIO channel. Note this is how some of us achieved a measure of redundancy for serial I/O before there was actual hardware redundancy . . .

If you have any caveats or suggestions I would welcome them.

-John

• DST
• Discrete Input card

John Rezabek

• 29 Mar 2018 9:27 PM
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2 Replies

• Andre Dicaire

  

  • 29 Mar 2018 9:39 PM

  John. You are correct. You can define the external reference of your existing parameters to point directly to an IO channel. With v12, IO references are no longer counted by Module, so even if one DI channel is used by more than one module, you'll only use one DI License for the channel. Prior to v12, if two modules referenced an IO channel, each module required a DST license.
  
  I suggest you setup a test module to make sure you've got the syntax right and all that. You should then be able to use a bulk edit file to populate the references.

  Andre Dicaire

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• Michael Krispin

  

  • 31 Mar 2018 3:14 AM

  In reply to Andre Dicaire:

  Hi Andre,
  my question might be off topic, but how is this with dynamic references. (BTW a really powerful function in DeltaV). I tried this one time in an older Version to link to a DST, but failed. I idea was to use only temporary specific diagnostic parameter of special devices (analytic, scale etc.) and share that way several DST to final target modules to reduce the license and module count.
  Thanks and Best Regards
  Michael

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