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Chapter 4
Connecting Signals
General-Purpose Timing Signal Connections
NI 6115/6120 User Manual
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Figure 4-29. UISOURCE Signal Timing
The maximum allowed frequency is 20 MHz, with a minimum pulse width
of 10 ns high or low. There is no minimum frequency limitation.
Either the 20 MHz or 100 kHz internal timebase normally generates
UISOURCE unless you select some external source.
The general-purpose timing signals are GPCTR0_SOURCE,
GPCTR0_GATE, GPCTR0_OUT, GPCTR0_UP_DOWN,
GPCTR1_SOURCE, GPCTR1_GATE, GPCTR1_OUT,
GPCTR1_UP_DOWN, and FREQ_OUT.
GPCTR0_SOURCE Signal
Any PFI pin can receive as an input the GPCTR0_SOURCE signal, which
is available as an output on the PFI8/GPCTR0_SOURCE pin.
As an input, GPCTR0_SOURCE is configured in the edge-detection mode.
You can select any PFI pin as the source for GPCTR0_SOURCE and
configure the polarity selection for either rising or falling edge.
As an output, GPCTR0_SOURCE reflects the actual clock connected to
general-purpose counter 0, even if another PFI is externally inputting the
source clock. This output is set to high-impedance at startup.
t
p
t
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t
= 50 ns minimum
p
t
= 10 ns minimum
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4-32
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