Re: [foxboro] system error in sequences

  • From: "Jones, Charles R. (Chuck)" <Chuck.Jones@xxxxxxxxxxxxxxx>
  • To: <foxboro@xxxxxxxxxxxxx>
  • Date: Fri, 27 Aug 2010 06:30:58 -0400

Dirk,
I have another suggestion (or maybe just a style point).  I try not to
put more than one network call into a single line of code.  For example:


        IF (:PRESS_CP4:PT_HOPPERR1.PNT - :LOGIC_PRESS:R1_PRESS.RO01) <
RI0002 AND :PRESS_CP4:PT_HOPPERR1.PNT < 5 THEN

In that line there are three calls to the network for information (one
is called twice).  Each call causes the current sequence to wait for at
least one BPC of the sequence block.  If one of the calls fails, how
will you know which is the problem?  The sequence block error message
will only give you the line number in the sequence.

Another way to write the same code would be to use some new variables:

        HOPPERR1   := :PRESS_CP4:PT_HOPPERR1.PNT;
        R1_PRESS   := :LOGIC_PRESS:R1_PRESS.RO01;
        DeltaPress := HOPPERR1 - R1_PRESS;

        IF (DeltaPress < RI0002) AND (HOPPERR1 < 5.0) THEN

It may only be a style point, but I have had fewer problems since I
started breaking things up.



Chuck Jones
Automation Technologist
Tate & Lyle Lafayette Plant




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