Gpctr1_Source Signal; Gpctr1_Gate Signal; Figure 4-33. Gpctr1_Source Signal Timing - National Instruments DAQ PCI E Series User Manual

Chapter 4 Signal Connections

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 output is set to
tri-state at startup.
Figure 4-33 shows the timing requirements for the GPCTR1_SOURCE
signal.
t
p
t t
w w
t
= 50 ns minimum
p
t
= 23 ns minimum
w

Figure 4-33. 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
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
© National Instruments Corporation 4-43 PCI E Series User Manual