Chapter 4 Signal Connections
National Instruments Corporation
4-33
DAQCard E Series User Manual
Scans generated by either an internal or external STARTSCAN signal
are inhibited unless they occur within a data acquisition sequence.
Scans occurring within a data acquisition sequence may be gated by
either the hardware (AIGATE) signal or software command register
gate.
CONVERT* Signal
Any PFI pin can externally input the CONVERT* signal, which is
available as an output on the PFI2/CONVERT* pin.
Refer to Figures 4-10 and 4-11 for the relationship of STARTSCAN to
the data acquisition sequence.
As an input, the CONVERT* signal 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 the CONVERT* signal initiates an A/D conversion.
As an output, the CONVERT* signal reflects the actual convert pulse
that is connected to the ADC. This is true even if the conversions are
externally generated by another PFI. The output is an active low pulse
with a pulse width of 50 to 100 ns. This signal is set to input (High-Z)
at startup.
Figures 4-20 and 4-21 show the input and output timing requirements
for the CONVERT* signal.
Figure 4-20.
CONVERT* Input Signal Timing
Rising-edge
polarity
Falling-edge
polarity
t
w
t
w
= 10 ns minimum
