Chapter 3
Connecting the Signals
DAQPad-MIO-16XE-50 User Manual
3-36
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The DAQPad-MIO-16XE-50 UI counter normally generates the UPDATE*
signal unless you select some external source. The UI counter is started by
the WFTRIG signal and can be stopped by software or the internal Buffer
Counter.
D/A conversions generated by either an internal or external UPDATE*
signal do not occur when gated by the software command register gate.
UISOURCE Signal
Any PFI signal can externally input UISOURCE, which is not available as
an output on the DAQPad-TB-52. The UI counter uses the UISOURCE
signal as a clock to time the generation of the UPDATE* signal. You must
configure the PFI signal you select as the source for the UISOURCE signal
in the level-detection mode. You can configure the polarity selection for the
PFI signal for either active high or active low. Figure 3-27 shows the timing
requirements for the UISOURCE signal.
Figure 3-27.
UISOURCE Signal Timing
The maximum allowed frequency is 20 MHz, with a minimum pulse width
of 23 ns high or low. There is no minimum frequency limitation.
Either the 20 MHz or 100 kHz internal timebase normally generates the
UISOURCE signal unless you select some external source.
t
p
= 50 ns minimum
t
w
= 23 ns minimum
t
w
t
w
t
p
