Document type:
Title:
Revision date:
Re vision:
User's Manual (MUT)
N1145 Quad Scaler and Preset Counter/Timer
05/11/2003
0
NPO:
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Page:
00115/01:N1145.MUTx/00
N1145_REV0.doc
14
12
4. Operating modes
4.1. Gated up-counting
When in NORMAL MODE, the counters (
sections 1 to 4
) do not require a GATE input.
However, when in GATE (or GATE+CLEAR) mode, a NIM/TTL signal must be supplied
at the GATE input of each counter used. NOTE: when using NIM input signals, this signal
has to be terminated with a 50
Ω
impedance at the other GATE bridged input, on
sections 1 or 3
.
A single GATE signal can be sent in parallel, to two channels via cables; if the last
section
is either
2 or 4
then this also provides the correct 50
Ω
cable termination. For
example
, sections 1 and 2
can share a GATE by feeding the external GATE signal to the
GATE input of
section 1
and then connecting a cable between the other GATE output of
section 1
to the GATE input of
section 2
, which has a 50
Ω
impedance. It is also possible
to connect three
sections
(for instance #1 with #3, and then #3 with #2 or #4) via cables,
in order to send them a single external GATE input.
The OUT signal of
section
5 can be used as the GATE input to the counters. The double
OUT connector permits parallel GATE feeding of all four
sections
, as described above.
4.2. 16- or 24- Digit Up-Counting
It is possible to increase the up-counting range to 16 or 24 digits by using the CARRY
outputs of
sections 2 and 4
.
For instance, 16-digit up-counting is obtained by connecting the CARRY output of
section 2
to the input of
section 1
. When the counter of
section 2
has fully cycled
(transition 99,999,999 to zero) the CARRY output supplies a NIM input pulse to
section 1
,
and so on. Thus
section 1
will show the most significant digits, and
section 2
the least
significant digits of the counting operation.
Similarly, for 24-digit up-counting, the CARRY output of
section 2
may be connected to
the input of
section 4
; the CARRY output of
section 4
may then be fed to the input of
section 1 or 3
.
4.3. Frequency measurements
This is a way of making relative frequency measurements.
By using
section 5
in TIMER MODE, it is possible to make a frequency measurement.
For that purpose:
•
select the clock rate:
ƒ
=1
/τ