Re: [foxboro] PID SPT parameter connectable/setable
- From: <Adam.Pemberton@xxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Sun, 14 Jan 2007 15:02:10 +1000
Does it help? Your answers always help Alex - but my confused mind is
rarely easy to untangle.
You saying SPT is an output is challenging, especially seeing it is
documented as an input. But I guess I can see what you mean because of
its LR behaviour.
In terms of your options, I would have assumed virtually all parameters
would be yes for options 1) and 3). Hence, aren't these somewhat
redundant? My assumption was that connectable refers to your option 4)
and settable refers to your option 2).
My particular reason for enquiring is I have written an application that
visualizes the I/A block interconnections based on the contents of an
SQL Server database. The database has a ParamTypes table containing all
the properties found in the documentation (and transferred to the
database through a very painful process of checking and double
checking).
The application finds all input and output connections for the current
block of interest using two SQL queries into the database. One of the
queries uses the connectable property of the ParamType to ignore
non-connectable parameters.
We use this application extensively to visualize our code and
discovering this inconsistency has rocked my faith in this application.
Do I have to go back and reassess each parameter's connectable status or
is this an isolated case of confusion/error?
Until now we have not noticed an inconsistency between what the
application is showing and what we find in ICC or the SELECT screen so I
assumed I had correctly interpreted the meaning of these two properties.
Apologises for the pedantic nature of this argument, but I'm hoping for
a deeper understanding of I/A from this thread.
Regards
Adam
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Johnson, Alex P (IPS)
Sent: Sunday, 14 January 2007 2:18 PM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] PID SPT parameter connectable/setable
I've never like the way the documentation is written. It's just
confusing, but it is a compromise made in order to provide a summary
table.
There are four possibilities:
1) Getable - one shot get can return a value
2) Setable - one shot set can change a value
3) Connectable for read - change driven values can be returned as
they occured on the scan period
4) Connectable for write - change driven values can be driven into
the value and the value is secured against
changes from any other source.
The SPT parameter is an output. Outputs cannot be connectable for write.
The SPT parameter may or may not be setable based on the state of the LR
switch. So, the correct and complete answer for SPT is:
1) Yes
2) Maybe depends on LR value
3) Yes
4) No
Does this help?
Alex
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx on behalf of
Adam.Pemberton@xxxxxxxxxxxx
Sent: Sat 1/13/2007 10:32 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] PID SPT parameter connectable/setable
The Foxboro documentation (I have up to Version 7.1) says that the SPT
parameter on all the PID blocks is connectable and not-settable.
It's my understanding that it's the other way around. You can set the
parameter from the SELECT screen or DM/FV but can only connect to the
RSP parameter.
Whose right?
Regards
Adam Pemberton
Site Electrical & Control Systems Engineer
Lihir Gold Limited
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