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<== Date ==> <== Thread ==>

Subject: Re: Help required
From: "Paduan Donadio, Marcio via Tech-talk" <tech-talk@aps.anl.gov>
To: EPICS tech-talk <tech-talk@aps.anl.gov>
Date: Thu, 1 Aug 2019 16:32:25 +0000
Hello, Cool Chips.

When an input field has a PV with PP (Process Passive), it forces the record to process before giving the result to the destination.

In your example, each 1 second "sum" will process. When this happens, it will ask for "A" and "B" to process and give them the data after it.

If you used NPP (Non Process Passive), "sum" would take whatever value is available in A and B, without having them process first.

For a Soft Channels AI, as in your example, this really is not a big deal. But imagine if A and B are attached to a physical device. They will read information from the device only when processing. With NPP, "sum" would have always read the same value over and over, even if the device is changing status.

I hope that helps.

Best regards,

Márcio Paduan Donadio
Control Systems Engineer - SLAC

On 7/31/19, 8:18 AM, "tech-talk-bounces@aps.anl.gov on behalf of Andrew Johnson via Tech-talk" <tech-talk-bounces@aps.anl.gov on behalf of tech-talk@aps.anl.gov> wrote:

    Cool Chips


References:
Fwd: Help required Andrew Johnson via Tech-talk

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