Chapter4 ConnectingSignals
©NationalInstruments Corporation 4-37 NI6013/6014 User Manual
Figure 4-32 showsthe timing requirements for GPCTR1_SOURCE.
Figure4-32. GPCTR1_SOURCE 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.
The20 M Hz or 100 kHz timebase normally generates GPCTR1_SOURCE
unlessyou select some external source.
GPCTR1_GATE Signal
Any PFIpin can ext ernally input the GPCTR1_GATE signal, which
is available as an output on the PFI4/GPCTR1_GATE pin.
As aninput, GPCTR1_GATE is configured in edge-detection mode.
Youcan select any PFI pin as the source for GPCTR1_GATEand configure
thepolarity selection for either rising or falling edge. You can use the gate
signali n a varietyof different applications to perform such actions as
startingand stopping t he counter,generating interrupts, saving the counter
contents,and so on.
As anoutput, GPCTR1_GATE monitors the actual gate signal connected
togeneral-purpose counter 1,even if the gate is being externally generated
byanother PFI. This output is set to high-impedance at startup.
t
w
=23 ns minimum
t
p
=50 ns minimum
t
w
t
w
t
p