
37
This system enables the experimenter to latch the state of all OR
outputs as they existed during the actual event time, even if the common
STOP arrives somewhat later than the end of the event time. The width
should be set to the desired coincidence resolution (the drift time of the
chamber). If the trigger outputs of several 3377 modules are to be
combined in a trigger system, an appropriate external clock should be
supplied to synchronize the trigger outputs. Otherwise the trigger
coincidence resolution must be increased to cover the random phase of
the clocks in each 3377 module.
Trigger Outputs in the
Common Start Modes
The eight prompt OR outputs are used as the clock input to flip flops
which are enabled by the common START signal, and disabled by the
end of acquisition (the common start time out). Any signal inputs during
this interval set the flip flop and are latched. Signals which arrive before
the common START or after the time out, are ignored. The latches are
not reset until the end of readout (when the system returns to acquisition
mode). A fast clear during the MPI will also clear the latches. If the
external common stop time out is used, there is no synchronization jitter,
and the coincidence resolution can be set precisely.