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

Subject: Re: Proposed change in asyn - request for comments
From: Bruce Hill <bhill@slac.stanford.edu>
To: Andrew Johnson <anj@aps.anl.gov>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 1 Jun 2012 16:27:32 -0700
Interesting!
I can see how that could be quite useful!
As we don't use post_event() for that purpose, I just
assumed it was a general purpose signaling mechanism.
It also works quite nicely for that purpose, as I used it to
implement a history mechanism in our EDT frame grabber.

Regards,
- Bruce

On 6/1/2012 7:55 AM, Andrew Johnson wrote:
Hi Bruce,

On 2012-05-31 Bruce Hill wrote:
My concern was that overloading the TSE field to contain EVR Event codes
would be inappropriate for a module like asyn that is used by many sites
that don't use EVR's.
The TSE and TSEL fields were originally /designed/ for use with timing system
event codes.  The Record Reference Manual describes the TSE field thus:

     This indicates the mechanism to use to get the time stamp. '0' - call
     get time as before '-1' - call the time stamp driver and use the best
     source available. '-2' - the device support provides the time stamp
     from the hardware. Values between 1-255 request the time of the last
     occurrence of a generalTime event.

   https://wiki-ext.aps.anl.gov/epics/index.php/RRM_3-14_dbCommon

I agree that this mechanism is not currently much use on systems that don't
use an event timing system, although it would be quite feasible to write a
plugin for the generalTime event subsystem that provides global event times
from UDP packets.

- Andrew

References:
Proposed change in asyn - request for comments Mark Rivers
RE: Proposed change in asyn - request for comments Kim, Kukhee
Re: Proposed change in asyn - request for comments Bruce Hill
Re: Proposed change in asyn - request for comments Andrew Johnson

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