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Chapter 4 Signal Connections
National Instruments Corporation 4-41 VXI-MIO Series User Manual
GPCTR1_SOURCE Signal
Any PFI pin can externally input the GPCTR1_SOURCE signal, which
is available as an output on the PFI3/GPCTR1_SOURCE pin.
As an input, the GPCTR1_SOURCE signal is configured in the
edge-detection mode. You can select any PFI pin as the source for
GPCTR1_SOURCE and configure the polarity selection for either
rising or falling edge.
As an output, the GPCTR1_SOURCE monitors the actual clock
connected to general-purpose counter 1. This is true even if the source
clock is being externally generated by another PFI. This signal is set to
input (High-Z) at startup.
Figure 4-32 shows the timing requirements for the GPCTR1_SOURCE
signal.
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.
The 20 MHz or 100 kHz timebase normally generates the
GPCTR1_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.
As an input, the GPCTR1_GATE signal is configured in edge-detection
mode. You can select any PFI pin as the source for GPCTR1_GATE and
t
p
t
w
t
w
t
p
t
w
= 50 ns minimum
= 23 ns minimum