National Instruments 6023E 用户手册
Chapter 4
Signal Connections
4-44
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Figure 4-35 shows the timing requirements for the GPCTR0_SOURCE
signal.
signal.
Figure 4-35. GPCTR0_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 the
GPCTR0_SOURCE signal unless you select some external source.
GPCTR0_SOURCE signal unless you select some external source.
GPCTR0_GATE Signal
Any PFI pin can externally input the GPCTR0_GATE signal, which is
available as an output on the PFI9/GPCTR0_GATE pin.
available as an output on the PFI9/GPCTR0_GATE pin.
As an input, the GPCTR0_GATE signal is configured in the edge-detection
mode. You can select any PFI pin as the source for GPCTR0_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 actions such
as starting and stopping the counter, generating interrupts, saving the
counter contents, and so on.
mode. You can select any PFI pin as the source for GPCTR0_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 actions such
as starting and stopping the counter, generating interrupts, saving the
counter contents, and so on.
As an output, the GPCTR0_GATE signal reflects the actual gate signal
connected to general-purpose counter 0. This is true even if the gate is
externally generated by another PFI. This output is set to high impedance
at startup. Figure 4-36 shows the timing requirements for the
GPCTR0_GATE signal.
connected to general-purpose counter 0. This is true even if the gate is
externally generated by another PFI. This output is set to high impedance
at startup. Figure 4-36 shows the timing requirements for the
GPCTR0_GATE signal.
t
p
t
w
t
w
t
p
t
w
= 50 ns minimum
= 23 ns minimum