National Instruments 3.21E+04 用户手册

Chapter 4     Signal Connections

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 National Instruments Corporation

4-47

AT-MIO/AI E Series User Manual

Any PFI pin can externally input the GPCTR0_GATE signal, which is 
available as an output on the PFI9/GPCTR0_GATE pin.

As an input, the GPCTR0_GATE signal is configured in the 
edge-detection mode.  You can select any PFI pin as the source for 
GPCTR0_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 actions such as starting and stopping the 
counter, generating interrupts, saving the counter contents, and so on.

As an output, the GPCTR0_GATE signal reflects the actual gate signal 
connected to general-purpose counter 0.  This is true even if the gate is 
being externally generated by another PFI.  This output is set to tri-state 
at startup.

Figure 4-32 shows the timing requirements for the GPCTR0_GATE 
signal.

Figure 4-32.  GPCTR0_GATE Signal Timing in Edge-Detection Mode

This signal is available only as an output on the GPCTR0_OUT pin.  
The GPCTR0_OUT signal reflects the terminal count (TC) of 
general-purpose counter 0.  You have two software-selectable output 
options— pulse on TC and toggle output polarity on TC.  The output 
polarity is software selectable for both options.  This output is set to 
tri-state at startup.  Figure 4-33 shows the timing of the GPCTR0_OUT 
signal.

Rising-edge
polarity

Falling-edge
polarity

t

w

t

w

= 10 ns minimum