Re: [foxboro] IND question

  • From: Corey R Clingo <corey.clingo@xxxxxxxx>
  • To: foxboro@xxxxxxxxxxxxx
  • Date: Mon, 1 Mar 2010 11:20:34 -0600

"Part of the issue is the external references - assuming it is outside the 
CP holding the IND block. 
If that is the case, each one of those will suspend the block for 1 BPC 
(minimum) which translates into 1 block period."

Alex,


If the external references are in the same CP, or compound, does this 
still hold?  Could you make connections to AIN blocks or whatever and then 
reference those in the HLBL without the time penalty?


Corey






"Johnson, Alex P (IOM)" <Alex.Johnson@xxxxxxxxxxxx> 
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Re: [foxboro] IND question






Part of the issue is the external references - assuming it is outside the 
CP holding the IND block. 

If that is the case, each one of those will suspend the block for 1 BPC 
(minimum) which translates into 1 block period.

So, at the minimum, your WAIT UNTIL is adding 1 block period delay.

Can you bring that value into a RIxxxx parameter? That would eliminate 
that delay. The same hold true for the external references in the rest of 
the code.


I once had a client call and complain that his safety shutdown logic took 
to long to run. I asked how is it implemented and how long does it take. 
He said it is 20 lines of sequence code and it takes 10s to complete. He 
sent the code with his reply. It was 20 external references in a block 
with a 0.5 PERIOD. I had to explain that what he saw is normal.

The fix? Bring the values in as connections.


Does this help?

Regards,
 
Alex Johnson
Invensys Operations Management
10900 Equity Drive
Houston, TX 77041
+1 713 329 8472 (desk)
+1 713 329 1600 (operator)
+1 713 329 1944 (SSC Fax)
+1 713 329 1700 (Central Fax)
alex.johnson@xxxxxxxxxxxx (current)
alex.johnson@xxxxxxxxxxxxxxxx (good until September 2010)

 



 
 
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