Re: CALC record question

[mooney@aps.anl.gov (Tim Mooney)]

re...,

> I am trying to reset a value used in a calculation record
> from a button on a 'dm' screen. The CALC field is set to
> A+1 and the VAL field is looped back to INPA, so that continual
> processing of the calculation record gives: 1, 2, 3, 4, etc.
> 
> I want a button on a 'dm' screen such that when it is pressed, the
> above calculation starts again at 0. I thought this should be easy
> but haven't managed it yet. 
>
> I tried letting the button press put the
> value 0 into INPB and changing CALC to B*{A+1} so that, 
> normally B=1 and we have as before. When the button is
> pressed, the record processes once with B=0 and then the
> whole thing starts again. 

You mean the 'dm' button writes '0' to the "B" field, not to the "INPB"
field, right?

> This doesn't work.
> I suppose because the above means that INPB needs to take two 
> inputs (the first, a hardwired 1, the second a 0 put into B when 
> the button is pressed). 
> In this case, how can the calculation record know which value it is 
> supposed to be using? Or am I going about this in totally the wrong way?

You have to arrange for B to contain '0' only until the reset
succeeds.  The calc record could FLNK to a BO record that puts
(NPP) a '1' into the B field.

You might also just write '0' to the VAL field, but the value change
would be immediate, rather than synchronous.

Tim Mooney