Chapter 4
Signal Connections
6711/6713/6715 User Manual
4-16
www.ni.com
Figure 4-9.
UPDATE* Output Signal Timing
The DACs are updated within 100 ns of the leading edge. Separate the
UPDATE* pulses with enough time that new data can be written to the
DAC latches.
The UI counter for the 671X device 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 pin can externally input the UISOURCE signal, which is not
available as an output on the I/O connector. The UI counter uses the
UISOURCE signal as a clock to time the generation of the UPDATE*
signal. You must configure the PFI pin you select as the source for the
UISOURCE signal in the level-detection mode. You can configure the
polarity selection for the PFI pin for either active high or active low.
Figure 4-10 shows the timing requirements for the UISOURCE signal.
Figure 4-10.
UISOURCE Signal Timing
t
w
t
w
= 50-75 ns
t
p
t
w
t
w
t
p
t
w
= 50 ns minimum
= 10 ns minimum
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