Chapter4 SignalConnections
6023E/6024E/6025EUser Manual 4-44 ni.com
Figure 4-35 showsthe timing requirements for the GPCTR0_SOURCE
signal.
Figure4-35. GPCTR0_SOURCE Signal Timing
Themaximum allowed frequency is 20 MHz, with a minimum pulse width
of 23 ns high or low.There is no minimum frequency limitation.
The 20M Hz or100 kHz timebase normally generates the
GPCTR0_SOURCE signal unless you select some external source.
GPCTR0_GATE Signal
Any PFIpin can ext ernally input the GPCTR0_GATE signal, which is
available as an output on the PFI9/GPCTR0_GATE pin.
Asan input, the GPCTR0_GATE signal is configured in the edge-detection
mode. Youcan select any PFI pin as the source for GPCTR0_GATE and
configurethe polarity selection for either rising or falling edge. You can use
thegate signal in a variety of different applications to perform actions such
asstartin g and stopping the counter,generating interrupts, saving the
counter contents, and so on.
As ano utput, the GPCTR0_GATEsignal reflects the actual gate signal
connected to general-purpose counter 0. This is true evenif the gate is
externally generated byanoth er PFI. This output is set to high impedance
at startup. Figure 4-36 showsthe timing requirements for the
GPCTR0_GATEsignal.
tp
twtw
tp
tw
=50 ns minimum
=23 ns minimum