Experimental Physics and
Industrial Control System

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.

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

References:

synchronizing data to an event Ron Rechenmacher

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