Emerson Exchange 365

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Profibus Analogue Slot

Is there a way to read a slot of Analogue Inputs into a register and use a similar instruction to BFO in a landing module? Therefore using 1 DST. I can see it's straight forward for a Digital Input/output slot. I have remote Turck I/O connected with Profibus, this is being moved from an S7 PLC into DeltaV.

Thanks

Jim M

• 4 Jun 2020 8:12 AM
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• Michael Moody

  

  • 4 Jun 2020 7:24 PM

  Jim, there are a few ways to do it.
  
  Just as you stated, a BFO can be used to parse the Analog signal into multiple Discrete signals. You can wire directly to internal parameters that are referenced by the control modules. I've also use CALC/ACT blocks to parse out to parameters so I could update status (when a status bit was included with the Profibus signal). BTW, you can also convert a single 32-bit Floating Point be converted into two 16-bit FPs. You will need to understand the bit pattern from the input / output signals to parse out correctly.
  
  Realize that while this can save on DSTs for Profibus (or Modbus / DeviceNet / etc.), it will also come with an impact on performance.
  1. Requires landing modules. Landing modules require additional CPU time to process.
  
  2. Considering all I/O points "managed" by the landing module are updated at the same frequency, it becomes a limiting factor and must have a scan rate to support the fastest control module referencing. This can require even more CPU usage.
  
  3. You may need to create custom composites for AIs, AOs, DIs, etc. as the landing module parameters are often not directly addressable in a standard I/O blocks IO address field. With the DC blocks, we used the F_IN_Dx & F_OUT_Dx
  
  4. Diagnostics for a channel will be limited to how well you parse out any error / status information that comes over the Profibus.
  
  Michael

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