National Instruments 3.21E+04 사용자 설명서
Chapter 4 Signal Connections
AT-MIO/AI E Series User Manual
4-46
National Instruments Corporation
General-Purpose Timing Signal Connections
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_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 externally input the GPCTR0_SOURCE signal, which
is available as an output on the PFI8/GPCTR0_SOURCE pin.
is available as an output on the PFI8/GPCTR0_SOURCE pin.
As an input, the GPCTR0_SOURCE signal 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.
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, the GPCTR0_SOURCE signal reflects the actual clock
connected to general-purpose counter 0. This is true even if another PFI
is externally inputting the source clock. This output is set to tri-state at
startup.
connected to general-purpose counter 0. This is true even if another PFI
is externally inputting the source clock. This output is set to tri-state at
startup.
Figure 4-31 shows the timing requirements for the GPCTR0_SOURCE
signal.
signal.
Figure 4-31. 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.
width 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.
t
p
t
w
t
w
t
p
t
w
= 50 ns minimum
= 23 ns minimum