Re: [foxboro] CALC vs. IND question
- From: "Kevin Beauchamp" <KBeauchamp@xxxxxxxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Wed, 26 Mar 2008 21:43:04 -0500
Mike,
The attached file is a simple test that I did in 2005 to verify the
difference in CP loading between CALC blocks and sequence (IND) blocks.
From a loading standpoint this test proved that CALC blocks should be
used when possible. It also proves that when you have to use a IND
block, global addressing should only be used when absolutely necessary.
You may be able to use this document to help solve your question.
Thank you,
Kevin M. Beauchamp
Engineering Manager
Galloway Company
920-886-2302 (office)
920-585-5080 (cell)
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Mike_Adams@xxxxxxxxxxxxx
Sent: Wednesday, March 26, 2008 4:45 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] CALC vs. IND question
Hello list,
I have some existing compounds in 4 I/A nodes that each have about 20
CALC blocks running at a 2 sec period with pretty good phasing. These
blocks are running somewhat arcane mathematical calculations with 15 to
25 steps each but only 2 or 3 real outputs are generated per CALC block.
The CALC steps are not commented at all. We are running into problems
where it is becoming harder to keep up with what is going on in these
CALCs and it is very hard to edit them efficiently. I am interested in
replacing these CALCs with IND blocks that would do the same work but be
much easier to troubleshoot, document & edit.
I know that INDs load the system more than CALCs but I'm not sure by
what degree. All 4 control processors involved are CP30s. Two of these
CPs are lightly loaded but the other 2 are heavily loaded.
If I configured an IND to run at the same period as a CALC and do the
same calculations, what would a reasonable guesstimate of the increase
in load be? I just want to get a rough idea on a 1:1 comparison for
starters.
I realize I can probably do the following to ease the load increase
incurred by going to INDs:
- lengthen the period to 5 sec & phase them well
- put 2 or 3 CALC blocks worth of steps into 1 IND
- place strategic WAIT statements in the IND code
Thanks in advance,
Mike Adams
Mitsubishi Polyester Film, LLC
Greer, SC USA
864-879-5231
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