National Instruments NI PCI-6110 - Manual (Page 54)

Chapter 4 Connecting Signals
NI PCI-6110/6111 User Manual 4-24 ni.com
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.
CONVERT* Signal
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