Re: [foxboro] Starting a scripts

However, as I have stated many times before, there are problems with this
approach that need to be address and which tend to make the application more
difficult than this example suggests.

In particular, 
*       if you reference the DMCMD variable for a DM/FV which is not
running, nothing will happen.
*       If someone else stores a value in that variable after you and before
the DM/FV scans it, your command is lost
*       If the variable does not exist or there is a problem accessing it
(excessive network traffic perhaps), the sequence block needs event handlers
to handle it or it will have an OPERR and stop. Recovery from this error is
difficult if more than one such assignment is made in the code.
*       The right command must be used, e.g., applic, run, wp_applic,
depending on where the program or script is to be run.
*       Synchronization of completion of the script with the sequence code
is frequently requireed.

All of these can lead to strange errors and intermittent failures. On the
other hand, if occasional, hard to diagnose failures are okay. knock
yourself out.


With regard to the polling script mentioned earlier, if you use omget to get
the data, you will generate broadcast messages which can have a significant
impact on the system. If instead omgetimp is used, the broadcasts will be
eliminated, but you might still be putting a load on the CBLAN or CP that it
might not appreciate. This depends on the frequency of the call.


Once again, if anyone wants a write-up on this topic. Send a request
directly to me. I will not send the document to those who use the list to
request it. In fact, I might be rude. 


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:   Schouten, Frits JF [SMTP:Frits.Schouten@xxxxxxxxxxxx]
        Sent:   Tuesday, April 23, 2002 3:29 PM
        To:     'foxboro@xxxxxxxxxxxxx'
        Subject:        Re: [foxboro] Starting a scripts 

        Hi Walter,

        The easiest and cheapest way is to have an Sequence block with an
input
        connected to your CIN and when it goes TRUE run a <LBUG>DMCMD
command.
        Following is the guts of on of my IND blocks.

        STATEMENTS
        WHILE (TRUE) DO    { forever }
         
          IF ( sample_cut ) THEN
             :C0WP04DMCMD := "dmcmd run /opt/c1/script/sample_cut.scr ",
seq_no;
          ENDIF;
          WAIT UNTIL NOT sample_cut;
         
        ENDWHILE;
        ENDSEQUENCE

        The <LBUG> station must be a AW or WP for this to work.
        And offcourse the script need to be on that station too.
        Cheers,
        Frits.

        -----Original Message-----
        From: Scott, Walter [mailto:wscott@xxxxxxxxx]
        Sent: Wednesday, 24 April 2002 01:33
        To: foxboro@xxxxxxxxxxxxx
        Subject: [foxboro] Starting a scripts 



        I would like to start a script  when a cin goes high is there a way
to do
        this.

        Walter Scott
        Birmingham Water Works 
        wscott@xxxxxxxxx
        205-254-0796

         
         
        
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