Chapter 4
Signal Connections
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National Instruments Corporation
4-27
Figure 4-20.
STARTSCAN Output Signal Timing
The CONVERT* pulses are masked off until the device 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 device 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 CONVERT* to the
DAQ sequence.
t
w
= 50-100 ns
a. Start of Scan
toff
t
off
= 10 ns minimum
Start Pulse
CONVERT*
STARTSCAN
STARTSCAN
b. Scan in Progress, Two Conversions per Scan
t
w
