34
bits 5-6
The test mode clock
0 = 100 nsec
1 = 200 nsec
2 = 400 nsec
3 = 800 nsec
bit 7
Not used, always reads 0
bit 8
Test enable. This must be 1 for test mode.
bits 9-15
Not used, always reads 0.
A simple example of Common START register setup
0 = 10FFH
buffered mode, CAMAC readout, leading edge only,
header always, module ID is 255
1 = 0000H
event numbers starts at zero, no MPI
2 = 0000H
16 hits allowed
3 = 0000H
no request delay (not used in buffered mode)
4 = 00C8H
time out at 10 microseconds.
5 = 0000H
test mode NOT selected
Common Start Time Out
The internal common start time out value selected in register 4 controls
the end of acquisition in steps of 50 nsec, with a 50 nsec jitter due to
clock synchronization. If the external common stop time out is used,
there is no synchronization jitter, and the coincidence resolution can be
set precisely.
Dead Time
After the common start time out the 3377 buffers the data. Buffering
takes typically 1.8
µ
s +200 nsec per hit. During this time the front panel
BUSY output is asserted and the module responds with Q=1 to an F27,
A1 command. Any inputs received at the front panel will be ignored
during this period. Only when buffering of the data is complete and the
BUSY is turned off is the module ready to receive data at the front panel
signal inputs. The module is now ready for a new event, beginning with
the common hit. If the single buffer mode is selected (see section
“Unbuffered Mode”) then busy will remain on until the data is read out of
the unit.
Front panel Clear
This input is used to clear an event in progress. The CLEAR signal is
synchronized internally with the 100 nsec system clock, and its behavior
exhibits 100 nsec of jitter due to the random phase of this clock with
respect to the external input signals.
The CLEAR is effective from COMMON START to the end of MPI. If MPI
is set to 0, then CLEAR is effective from COMMON START to the
COMMON START TIME OUT. Note that the COMMON START TIME
OUT period is effectively an ‘MPI’. Note that CLEAR is ALWAYS permit-
ted during the COMMON START TIME OUT period. To be reliable, the