Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Fri, 22 Mar 2013 01:00:12 +0100

Am Donnerstag, 21. März 2013, 21:46:31 schrieb Eric Norum:
> Now I read the original article more closely.
> Tim's suggestion is a lot better…..

Your (Eric) solution should work reliably, too, if you are using a recent
release of version 2.1 of the sequencer and enable the safe mode (+s) option.
Safe mode guarantees that the value of 'bin' does not change asynchronously
after evaluation of the when-conditions has been triggered, until the state-
change action block finishes. If we get another event that resets the value to
bin=0, the state set does not see this new value until the next time when-
conditions are evaluated.

Indeed, this is one of the problems that safe mode was designed to solve.

BTW, it is possible to increase the pulse length of a transient signal in the
database using a seq+bo record. The following database demonstrates the
technique:

record(calcout,"timebase") {
    field(INPA,"timebase")
    field(CALC,"!A")
    field(SCAN,"2 second")
    field(OUT,"transientPulse PP")
}
record(bo,"transientPulse") {
    field(HIGH,"0.1")
}
record(seq,"triggerPulse") {
    field(DOL1,"transientPulse CPP")
    field(LNK1,"oneSecondPulse PP")
    field(DLY2,"1.0")
    field(DOL2,"0")
    field(LNK2,"oneSecondPulse PP")
}
record(bo,"oneSecondPulse") {
}

Cheers
Ben

> On Mar 21, 2013, at 1:43 PM, Eric Norum <[email protected]> wrote:
> > How about the following?
> >
> > int bin;   assign bin to "abc:bin";     monitor bin;
> > ss ttt {
> >
> >    state isZero {
> >
> >        when(bin == 1) {
> >
> >            printf("Received a trigger!!\n");
> >
> >        } state isOne
> >
> >    }
> >    state isOne {
> >
> >        when(bin == 0) { } state isZero
> >
> >    }
> >
> > }
> >
> > On Mar 21, 2013, at 10:04 AM, Tim Mooney <[email protected]> wrote:
> >> Hi Song,
> >>
> >> I have not done this myself in SNL, but if I needed to do it, I'd start
> >> by looking into the "syncq" and "pvGetQ" commands in the SNL Reference
> >> Manual:
> >>
> >> http://www-csr.bessy.de/control/SoftDist/sequencer/Reference.html
> >>
> >>
> >> Tim
> >>
> >> ----- Original Message -----
> >>
> >>> From: "Song Hu" <[email protected]>
> >>> To: [email protected]
> >>> Sent: Thursday, March 21, 2013 10:58:28 AM
> >>> Subject: how to trigger on positive edge only  with snl
> >>>
> >>> Hi,
> >>>
> >>> I would like to trigger some actions when a binary PV changes from 0
> >>> to 1. No action should be taken when it changes from 1 to 0. I made
> >>> some code like:
> >>>
> >>> int bin;                  assign bin to "abc:bin";
> >>>
> >>>                                  monitor bin;
> >>>
> >>>                               evflag  binFlag;
> >>>
> >>>
sync
> >>>
> >>>                                bin   binFlag;
> >>>
> >>> ss ttt
> >>> {
> >>> state testState
> >>> {
> >>>
> >>>    when(efTestAndClear(binFlag)&&(bin == 1))
> >>>    {
> >>>
> >>>          printf("Received a trigger!!\n");
> >>>
> >>>    }state testState
> >>>
> >>> }
> >>> }
> >>>
> >>> When abc:bin changes from 0 to 1 and then quickly go back to 0, it is
> >>> not working every time.
> >>>
> >>> What is the appropriate way to implement such positive edge only
> >>> trigger?
> >>>
> >>> Thanks in advance for your help.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System