Re: [foxboro] Calculations IND block
- From: "Johnson, Alex (Foxboro)" <ajohnson@xxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Mon, 6 May 2002 10:37:47 -0400
Please note, the core of Bram's answer is correct.
* External references do generate a network message for each such
reference
* External references to top level names that are not in the same
station do suspend the sequence block
I just want to point out that the traffic is not always a broadcast message
and that not all external references suspend the block.
Regards,
Alex Johnson
System Products - Invensys Systems, Inc.
10707 Haddington
Houston, TX 77043
713.722.2859 (office)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx <mailto:ajohnson@xxxxxxxxxxx>
Come to the Invensys Showcase: http://www.invensysshowcase.com/
<http://www.invensysshowcase.com/>
-----Original Message-----
From: Johnson, Alex (Foxboro) [SMTP:ajohnson@xxxxxxxxxxx]
Sent: Monday, May 06, 2002 9:04 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Calculations IND block
Re: Another issue is that external references increase network load
because
each external reference to another CP causes a broadcast.
Not necessarily so.
Before the OM issues a broadcast as a result of an external
reference, it
checks the IMPORT table for the top level name in the external
reference
(compound name or SV name).
If the top level name is in the IMPORT table, the associated station
address
is used to eliminate the need for a broadcast.
If the top level name is not found in the IMPORT table, a broadcast
is
issued. Once the station holding the target is known, the top leve
name is
added to the IMPORT table along with its station's address so that
subsequent access of that top level name do not require a broadcast.
For those that use the OM API, the external reference is implemented
as a
getval() call with the IMPORT flag set.
Re: Another interesting point about Sequence Block external
references
If the external reference is to a compound in the same station with
the
sequence block, the sequence block does not suspend. However, the
operation
is quite slow.
Regards,
Alex Johnson
System Products - Invensys Systems, Inc.
10707 Haddington
Houston, TX 77043
713.722.2859 (office)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx <mailto:ajohnson@xxxxxxxxxxx>
Come to the Invensys Showcase: http://www.invensysshowcase.com/
<http://www.invensysshowcase.com/>
-----Original Message-----
From: Marsman, Bram [SMTP:bmarsman@xxxxxxxxxxx]
Sent: Monday, May 06, 2002 4:25 AM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: Re: [foxboro] Calculations IND block
Hi,
The fact that you are using include-files has no influence
on the
time it
takes to finish your calculation. What you probably mean is
that you
are
using external references. (C:B.P)
Each time you assign a value in your sequence from a block
in
another CP via
external reference, the sequence code will suspend 1 period
of the
block.
So if your sequenceblock runs at 2 seconds, getting 5
variables
takes 10
seconds!
Another issue is that external references increase
networkload
because each
external reference to another CP causes a broadcast.
Especially in
the case
of continuous calculations with multiple values from
different CPs,
the
external reference should be avoided.
The solution is to connect your variables to the RI00xx
parameters
of the
sequenceblock and use user-labels in your code.
Your calculation will speed up and you network load will
decrease.
Bram Marsman.
-----Original Message-----
From: jdesaeve@xxxxxxxxxxx [mailto:jdesaeve@xxxxxxxxxxx]
Sent: maandag 6 mei 2002 10:56
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Calculations IND block
Hi,
I am writing sequence logic in IND blocks and using lots of
datapoints from
other stations.
Using " include files" rather than using direct links to
datapoints
in
other stations, it takes a lot of time before calucations
are done.
All blocks (for that specific project) have a period of 2
seconds
but
calculations are not finished at all during that time period
!
I would like to group all my blocks in one compound for that
project .
How to speed up the calculations ?
Regards,
Jef Desaever
Du Pont Protein Technologies
Zwaanhofweg 1
8900 Ieper-Belgium
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