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If you are performing an internally timed acquisition, NI-DAQ generates 
three extra points to clock the data for you. However, if you perform an 
externally clocked acquisition, NI-DAQ does not know when the last point 
is taken, so you must provide the three extra pulses.

Any PFI pin can receive as an input the CONVERT* signal, which is 
available as an output on the PFI2/CONVERT* pin.

Refer to Figures 4-9 and 4-10 for the relationship of CONVERT* to the 
DAQ sequence.

As an input, CONVERT* is configured in the edge-detection mode. 
You can select any PFI pin as the source for CONVERT* and configure 
the polarity selection for either rising or falling edge. The selected edge 
of CONVERT* initiates an A/D conversion.

As an output, CONVERT* reflects the actual convert pulse that is 
connected to the ADC, even if another PFI is externally generating the 
conversions. The output is an active low pulse with a pulse width of 50 to 
100 ns. This output is set to high-impedance at startup.

Figures 4-17 and 4-18 show the timing requirements for CONVERT*.

Figure 4-17.  CONVERT* Input Signal Timing

Rising-Edge

Polarity

Falling-Edge

Polarity

t

w 

= 10 ns minimum

t

w