Chapter 3
Connecting the Signals
DAQPad-MIO-16XE-50 User Manual
3-40
ni.com
Figure 3-31 shows the timing requirements for the GPCTR1_SOURCE
signal.
Figure 3-31.
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 signal can externally input GPCTR1_GATE, which is available as
an output on the PFI4/GPCTR1_GATE screw terminal.
As an input, the GPCTR1_GATE signal is configured in edge-detection
mode. You can select any PFI screw terminal 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 actions as starting and stopping the counter,
generating interrupts, saving the counter contents, and so on.
As an output, the GPCTR1_GATE signal monitors the actual gate signal
connected to general-purpose counter 1, even if the gate is being externally
generated by another PFI. This output is set to high-impedance at start up.
t
w
= 23 ns minimum
t
p
= 50 ns minimum
t
w
t
w
t
p
