Re: [foxboro] Setting Application Objects from IND blocks

Sachsa,

You are absolutely correct on BPCSTM. I should have written per block
period. I generally run my sequence blocks at the BPC, but I should not
assume that.

With regard to suspension, what you are seeing is correct. The CP =
supports
one outstanding request at a time. Other requests are queued.

So, the block processing would be something line:

1) BPC1
        a) IND1=20
                  i) Makes an external reference to a missing point
                 ii) The request is queued for processing
                iii) The block suspends.
        b) IND2=20
                  i) Make an external reference=20
                 ii) The request is queued
                iii) The block suspends

2) BPC2
        a) IND1
                  i) Wakes up
                 ii) Checks for value
                iii) Value not available
                 iv) Suspends =09
        b) IND2
                  i) Wakes up
                 ii) Checks for value
                iii) Value not available
                 iv) Suspendsand the requested is queued and the block
suspends

and so on and so on until the first request clears.

Make sense?


Regards,
=20
Alex Johnson
Invensys Process Systems
Invensys Systems, Inc.
10707 Haddington
Houston, TX 77043
713.722.2859 (voice)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx

-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx =
[mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Sascha Wildner
Sent: Thursday, November 18, 2004 8:38 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Setting Application Objects from IND blocks

Johnson, Alex (Foxboro) wrote:

> 2) The BPCSTM parameter will limit the number of statements per BPC.

Well, a coworker and I had an argument about this a while ago, so we =
did=20
some tests. Just for the record: It seemed to me that the BPCSTM=20
parameter - despite its name - rather limits statements per period. If =
I=20
remember correctly it was on a CP with a BPC of 0.1 sec. But it could=20
well be that we misinterpreted our results.

> 4) External references like yours (:A:O.A :=3D 2) will suspend the =
block's
> execution.

Not only the execution of the block containing the reference, it seems. =

In a project I recently did there was a typo in an external reference.=20
This causes the IND block to pause until searching for the reference =
had=20
timed out. After that, it gave an error but since it was forced to AUTO =

and ACTIVE it directly tried again. So far, so good. The, um,=20
"interesting" side effect was: This typo not only caused the IND block=20
containing it to pause until timeout, but rather _ALL_ IND blocks=20
running in that CP stopped resolving external references until the time =

out of the misspelled one was over. This decreased performance of our=20
sequence blocks dramatically and it took us a while until we figured it =

out. We even exchanged the CP before. :|

--=20
Gru=DF,

Sascha Wildner
erpicon Software Development GmbH
Neusser Str. 724-726
50737 K=F6ln
Germany

Phone: +49 221 9746069
Fax:   +49 221 9746099
eMail: swildner@xxxxxxxxxx

=20
=20
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