Chapter4 SignalConnections
©NationalInstruments Corporation 4-43 6023E/6024E/6025EUser Manual
signal. You must configure the PFI pin you select as the source for the
UISOURCE signal in the level-detection mode. You can configure the
polarity selection for the PFI pin foreither active highor active low.
Figure 4-34 shows the timing requirements for the UISOURCE signal.
Figure4-34. UISOURCE Signal Timing
Themaximum allowed frequency is 20 MH z, with a minimum pulse width
of 23 ns high or low.There is no minimum frequency limitation.
Either the 20 MHz or 100 kHz internal timebase normally generates the
UISOURCE signal unlessyou select some external source.
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_SOURCE Signal
AnyPFI pin can extern ally input the GPCTR0_SOURCE signal, which is
available as an output on the PFI8/GPCTR0_SOURCE pin.
As ani nput, the GPCTR0_SOURCE signal is configured in the
edge-detectionm ode. Youcan select any PFI pin as the source for
GPCTR0_SOURCE and configurethe polarity selection for either rising
or falling edge.
As ano utput, the GPCTR0_SOURCE signal reflects the actual clock
connected to general-purpose counter 0. This is true even ifano ther PFI
is externallyinpu tting the source clock. This output is set to high
impedance at startup.
tp
twtw
tp
tw
=50 ns minimum
=23 ns minimum