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Chapter 4
Connecting Signals
© National Instruments Corporation
4-37
Figure 4-32 shows the timing requirements for GPCTR1_SOURCE.
Figure 4-32. GPCTR1_SOURCE Signal Timing
The maximum allowed frequency is 20 MHz, with a minimum pulse width
of 23 ns high or low. There is no minimum frequency limitation.
of 23 ns high or low. There is no minimum frequency limitation.
The 20 MHz or 100 kHz timebase normally generates GPCTR1_SOURCE
unless you select some external source.
unless you select some external source.
GPCTR1_GATE Signal
Any PFI pin can externally input the GPCTR1_GATE signal, which
is available as an output on the PFI4/GPCTR1_GATE pin.
is available as an output on the PFI4/GPCTR1_GATE pin.
As an input, GPCTR1_GATE is configured in edge-detection mode.
You can select any PFI pin as the source for GPCTR1_GATE and configure
the polarity selection for either rising or falling edge. You can use the gate
signal in a variety of different applications to perform such actions as
starting and stopping the counter, generating interrupts, saving the counter
contents, and so on.
You can select any PFI pin as the source for GPCTR1_GATE and configure
the polarity selection for either rising or falling edge. You can use the gate
signal in a variety of different applications to perform such actions as
starting and stopping the counter, generating interrupts, saving the counter
contents, and so on.
As an output, GPCTR1_GATE monitors the actual gate signal connected
to general-purpose counter 1, even if the gate is being externally generated
by another PFI. This output is set to high-impedance at startup.
to general-purpose counter 1, even if the gate is being externally generated
by another PFI. This output is set to high-impedance at startup.
t
w
= 23 ns minimum
t
p
= 50 ns minimum
t
w
t
w
t
p