Re: synchronizing data to an event

[Till Straumann <strauman@slac.stanford.edu>]

Here at SLAC, the lcls and spear3 projects
abuse a number of bits in the nanosecond part
of the EPICS timestamps to carry a 'pulse ID' number
which is obtained from the timing system.
Data from all over the machine can then be aligned
using this pulse ID.
A hack - but it has proven to be quite useful
w/o the need for changing the CA protocol.

-- Till

Ron Rechenmacher wrote:
> Hi,
>
> I did a search of tech-talk for: timing event synchronization
> The results along with my experience to date leads to the conclusion
> that synchronization by 8 byte time stamp is the only synchronization that
> CA currently provides. (please correct if wrong)
>
> The question:
>
>   I was wondering if there has ever been any (perhaps behind the scenes)
>   discussion of adding additional synchronization information to the
>   Channel Access protocol?
>
>
> Perhaps, in addition to the timestamp, a "synchronizing event" structure, 
> which would be NULL if not used, but would otherwise have an event type and 
> event count.
>
> At some linear accelerator facilities, there has been a move toward counting 
> RF pulses and associating data collection triggered by the RF pulse with that 
> pulse count.  Of course there would be a pulse count to time correlation also,
> but many people seem to embrace the main data association (in archived data) 
> being with an event count.
>
> I've heard that there has been work on "beam flavors" at SLAC. (sorry if this 
> is bogus information). But if in addition to a timestamp, data also has 
> "flavor" information, then this could be considered a start to additional 
> synchronization information?  Has there been work on this? and if so, has any 
> progress reports been published?
>
> Thanks,
> Ron
>
>
>