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						June 8, 1995

The Trigger Electronics Subsystem Scope
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This note is intended to indicate the large amount of trigger-related
work needed to be done.  Clearly, we will need a lot of help from
people working on almost all aspects of BaBar.

So here is a first stab at trying to define the trigger electronics
subsystem.  Comments are welcome.

Draft of trigger scope:

  1) All filter algorithms that operate in real time.  In terms of the
TDR terminology, this means filter algorithms in the Level 1, Level 2
and Level 3 triggers.  These filters include:
    (a) Level 1 firmware algorithms operating in the drift chamber
(DC) segment finders, the EM calorimeter (EM) tower adders, the
central DC trigger, the central EM trigger and the global (GL)
trigger;
    (b) Level 2 software algorithms; and
    (c) Level 3 software algorithms.

  2) A subset of the relevant hardware executing the filter
algorithms.  Most notably, the hardware for the Level 1 central
triggers (DC, EM and GL).

  3) All interface definitions (jointly with the other sides of those
interfaces).  These interfaces are:
    (a) Level 1 interfaces to DC front-end, EM front-end, fast control
system, DAQ data path Level 2 trigger, and online system (run control,
slow electronics control, etc.).
    (b) Level 2 interfaces to Level 1 trigger, silicon vertex tracker
(SVT) occupancy data, DAQ data path, and online system.
    (c) Level 3 interface to DAQ data and online reconstruction.

  4) Software and firmware directly associated with trigger data.
This includes:
    (a) Level 1 data-formatting firmware and software for the DAQ data path.
    (b) Level 2 data-formatting software for the DAQ data path.
    (c) Level 3 trigger data formatting for mass storage.

  5) Reconstruction code for online and offline trigger
reconstruction, including data model to facilitate trigger efficiency
analysis studies (jointly with physics working groups).

  6) Simulation code for design studies and for efficiency analysis
studies, to be compared with real data (jointly with simulation
groups).  This includes detailed models of physics signal and of
non-annihilation backgrounds (jointly with simulation, backgrounds and
physics groups).

  7) Cooperation with the IR and backgrounds groups, not only in
simulating predicted backgrounds but in measuring real backgrounds as
the machine turns on (long before the final trigger system is
installed).