Document type:
Title:
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Re vision:
User's Manual (MUT)
N1145 Quad Scaler and Preset Counter/Timer
05/11/2003
0
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00115/01:N1145.MUTx/00
N1145_REV0.doc
14
10
input pulse the OUT ports become true. The counter is then decremented by the input
pulses until zero is reached. At the trailing edge of the last input pulse:
the OUT outputs are reset to FALSE (0 V).
the END MARKER output generates a NIM pulse whose length can be adjusted between
50 ns and 1 µs by acting on the trimmer next to the END MARKER connector; this signal
is
retriggerable
, thus it can be extended while active by another completed cycle. If the
END MARKER is used for retriggering purposes (it is sent to the LOAD connector), a
delay larger than the END MARKER duration is required between these connectors.
This arrangement allows direct use of the OUT ports as GATE inputs to the counters of
section 1 to 4.
CYCLING of Section 5 is controlled by the SINGLE
/
REPEAT switch, which is labelled
SGL
/
REP.
In SINGLE mode
the selected function (PRESET COUNTER or TIMER) is
performed only once, until zero is reached. In order to restart
the counter, a new load operation is required. Actually, when
using the LOAD button, the counter can be restarted even
BEFORE zero is reached. The LOAD NIM/TTL signal is
disabled during counting. After a LOAD via pushbutton, the unit
requires 80 ns at least before accepting LOAD pulses, even if
the counter is already zero and thus the cycle completed.
In REPEAT mode
a few seconds after zero is reached the counter re-triggers
itself automatically, by performing an automatic LOAD, and a
new cycle is restarted. The automatic LOAD takes place every
2 seconds after every cycle end. This procedure is repeated
indefinitely; anyway, the LOAD button allows to restart the
counter at any time. The LOAD NIM/TTL is always useless in
REPEAT mode.
Note that by connecting the END MARKER output to the LOAD input the counter is
cycled without the time delay of the REPEAT mode.
Important Note
: one or more of the following operations may lead the Section 5 to an
incorrect operation:
−
The use of an external clock with frequency larger than 80 MHz
−
The use of an external clock with pulse width shorter than 3 ns
−
The variation during the counter operation of the external clock frequency
−
The switching from internal clock to external or vice versa
In any case the counter normal operation is recovered by performing a manual/electrical
LOAD.
