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B-31
Counters Timing Diagrams
This section describes input delays, input requirements, output delays, gating modes, and
quadrature and two pulse encoder timing.
Input Delays
This section describes some of the timing delays of the counter/timer circuit. To describe delays
of the counter/timer, we model the circuitry as shown in Figure B-41. In the figure, PFI, RTSI,
and PXI_STAR represent signals at connectors pins of the M Series device. The other named
signals represent internal signals.
t
14
DO Sample Clock
P0
7.5
27.5
t
15
DO Sample Clock
PFI (output)
8.0
29.8
t
16
†
PFI (output) high
PFI (output)
low
Two periods of
80 MHz
Timebase
Three periods
of 80 MHz
Timebase
*
The delay ranges given for PFI and RTSI represent the fastest and slowest terminal routing within the
trigger group for a given condition (maximum or minimum timing). This difference can be useful when
two external signals will be used together and the relative timing between the signals is important.
†
When DO Sample Clock is routed to a PFI output pin, the pulse width of the output is independent of
the pulse width of the input. The pulse width is specified in a number of periods of the 80 MHz Timebase.
Table B-25.
DO Timing Requirements
Time
Requirement
Condition
Min (ms)
Max (ms)
t
10
PFI, RTSI, or
PXI_STAR
minimum period
When used as
DO Sample
Clock
NI 622
x
devices: 1000.0
NI 625
x
/NI 628
x
devices: 100.0
—
t
11
PFI, RTSI, or
PXI_STAR
minimum pulse
width
When used as
DO Sample
Clock
12.0
—
Table B-24.
DO Timing Delays (Continued)
Time
From
To
Min (ns)
Max (ns)
Содержание PCI-6281
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