Chapter 4
Signal Connections
PCI-MIO E Series User Manual
4-34
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National Instruments Corporation
The CONVERT* pulses are masked off until the board generates the
STARTSCAN signal. If you are using internally generated conversions,
the first CONVERT* appears when the onboard sample interval counter
reaches zero. If you select an external CONVERT*, the first external
pulse after STARTSCAN generates a conversion. The STARTSCAN
pulses should be separated by at least one scan period.
A counter on your PCI-MIO E Series board internally generates the
STARTSCAN signal unless you select some external source. This
counter is started by the TRIG1 signal and is stopped either by software
or by the sample counter.
Scans generated by either an internal or external STARTSCAN signal
are inhibited unless they occur within a DAQ sequence. Scans occurring
within a DAQ 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 4-11 and 4-12 for the relationship of STARTSCAN to
the DAQ 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
being externally generated by another PFI. The output is an active low
pulse with a pulse width of 50 to 100 ns. This output is set to tri-state at
startup.
Figures 4-21 and 4-22 show the input and output timing requirements
for the CONVERT* signal.
