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Maximum Time Range
Offset
bits 4-15
The Offset to be subtracted from the data before shifting
and readout, in units of 8 nsec. Bit 4 has a value of
8 nsec. This value must be set in a manner consistent with
the setting of the maximum time range in register 2.
Default is 0.
A simple example of Common STOP register setup:
0 = 10FFH
buffered mode, CAMAC readout, leading edge only,
0.5 nsec resolution, header always, module ID is 255
1 = 00FFH
event numbers starts at zero, no MPI, 25 nsec trigger
clock, maximum trigger width and delay
2 = 03F0H
full scale is 511 nsec, 16 hits allowed
3 = 0000H
zero offset, and no request delay (not used in buffered
mode)
The maximum time range is implemented inside the MTD133 monolithic
integrated circuit. The range is from 15 counts (7.5 nsec) to 65535
counts (32767.5 nsec). Any data which is GREATER THAN the maxi-
mum time range is discarded inside the MTD133 and exacts no readout
time penalty. Any data which is EQUAL TO or LESS THAN the maximum
time range can be readout.
The maximum time range is set in register 2. Only the upper 12 bits of
the 16 bit word are used for the maximum time range. These 12 bits are
compared to the upper 12 bits of the data words inside the MTD133. The
lower 4 bits are ignored by the hardware inside the MTD133. The
maximum data value which can be readout is equal to the maximum
time range value + 15 counts, or a multiple of 8 nsec +7.5 nsec. A value
of zero (for the upper 12 bits) allows readout of all data words of 15
counts (7.5 nsec) or less.
The Offset register is implemented on the 3377 board, in the program-
mable gate array chip. Only the upper 12 bits of this 16 bit word can be
set. The lower 4 bits are effectively set to zero. The offset is subtracted
from the data read from the MTD133, before the shift is applied. If the
data is GREATER THAN or EQUAL to the offset, the result of the
subtraction is then shifted (to choose the resolution) and becomes the
data to be stored in the FIFO buffer. If the data is LESS THAN the offset,
the data is discarded and no data word is stored.
It is possible to implement a time window, using the maximum time
range as the upper end and the offset value as the lower end. The upper
end is the maximum time range setting + 7.5 nsec. The lower end is the
offset value. These two values must be set properly for the resolution
and edge mode selected, or the data will be ambiguous. The offset must
be less than the maximum time range, and greater than or equal to the
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