All about PhotonFinish2 protocols (Rabbit version)
========================================================
Started 2014 Feb 3   Astummer@physics.utoronto.ca
Revised ...


EVENT AND TIME RECORD DESCRIPTIONS
==================================
- Each photon arrival ("event") is timestamped in realtime, arbitrary start time.
- Events are added to a packet, then when the packet is full (375 events), it is sent to the host via UPD/IP.
- Timing is reported as the number of typically 81pS intervalsrc as a 24-bit word (which rolls over).
- There are seven photon channels, 1 to 7.
- Channel 8 is a 1mS fiducial (time stamp).
- All events are counted in the 5-bit event counter (which rolls over), so that the data can be confirmed as contigious.
- Each event uses four bytes:
  MS Byte[7:3]: 5-bit event counter
         [2:0]: 3-bit channel number (as 0-7)
  next byte:    Timing, MS
  next byte:    Timing
  LS byte:      Timing, LS