User manual

Chapter 4 Connecting Signals
NI 6034E/6035E/6036E User Manual 4-30 ni.com
Figure 4-22. CONVERT* Output Signal Timing
The sample interval counter on the NI 6034E/6035E/6036E device
normally generates the CONVERT* signal unless you select some external
source. The counter is started by the STARTSCAN signal and continues to
count down and reload itself until the scan is finished. It then reloads itself
in preparation for the next STARTSCAN pulse.
A/D conversions generated by either an internal or external CONVERT*
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.
AIGATE Signal
Any PFI pin can externally input the AIGATE signal, which is not
available as an output on the I/O connector. The AIGATE signal can mask
off scans in a DAQ sequence. You can configure the PFI pin you select as
the source for the AIGATE signal in either the level-detection or
edge-detection mode. You can configure the polarity selection for the
PFI pin for either active high or active low.
In the level-detection mode if AIGATE is active, the STARTSCAN signal
is masked off and no scans can occur. In the edge-detection mode, the first
active edge disables the STARTSCAN signal, and the second active edge
enables STARTSCAN.
The AIGATE signal can neither stop a scan in progress nor continue a
previously gated-off scan; in other words, once a scan has started, AIGATE
does not gate off conversions until the beginning of the next scan and,
conversely, if conversions are being gated off, AIGATE does not gate them
back on until the beginning of the next scan.
t
w
=50to150ns
t
w
UM.book Page 30 Monday, May 14, 2001 10:32 AM