Re: [foxboro] HLBL question
- From: "Johnson, Alex P (IOM)" <alex.johnson@xxxxxxxxxxxxxxxx>
- To: "foxboro@xxxxxxxxxxxxx" <foxboro@xxxxxxxxxxxxx>
- Date: Tue, 19 Jan 2010 21:10:41 -0600
Tim,
I can't think of any possible benefit to the code as written.
As Dave mentions, it will be quite slow if the CBP referenced is in a different
CP since the block will suspend twice (once for each external reference).
I once had a client complain that his shutdown logic took too long to execute -
10s. It was 20 lines of like this:
C01:B.P := FALSE;
...
C20:B.P := FALSE;
which does in fact take 20s to complete if the block has a 0.5s PERIOD>
I wonder if this might have been done to take advantage of the timing? If so, a
WAIT statement would be better.
One more point, even internal references aren't fast. If you have a lot of
internal references in a row, you might be surprise at the load they place on
the CP.
Regards,
Alex Johnson
Invensys Process Systems
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@xxxxxxxxxxxxxxxx
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Lowell, Timothy
Sent: Tuesday, January 19, 2010 6:10 PM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: [foxboro] HLBL question
Oh, HLBL gurus,
We have some HLBL code at one of our sites that looks like this:
IF :CMP:BLOCK.MA THEN
:COMP:BLOCK.MA := FALSE;
ENDIF;
So, If the .MA parameter is true (block is in AUTO), then set the .MA parameter
to false (set block to MANUAL). If the block is already in MANUAL, move on.
Is this superior in any way, shape, or form to one simple command:
:CMP:BLOCK.MA := FALSE;
meaning, go ahead and send the command to set the .MA parameter to false, even
if it is already false?
We're thinking that in the first case, the IND block has to go and grab the
status of the .MA parameter, and then if it is true, change it, but if not,
leave it alone. We can't figure out why that would be better than just sending
a .MA := FALSE command no matter what. Either way, the IND block is
interacting with the Object Manager at least once, and in the first case
possibly twice, while in the second case you know that it will only interact
with the Object Manager once, even if it doesn't need to.
Any thoughts? Does reading from the OM in an IND block take up significantly
fewer resources that writing to it?
Tim Lowell
Tesoro Companies, Inc.
19100 RidgeWood Parkway
San Antonio, TX 78259
210-626-4929 (w)
210-253-0225 (c )
timothy.lowell@xxxxxxxxxxx<mailto:timothy.lowell@xxxxxxxxxxx>
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