User manual

Chapter 4 Connecting Signals
© National Instruments Corporation 4-33 NI 6034E/6035E/6036E User Manual
As an output, the UPDATE* signal reflects the actual update pulse that is
connected to the DACs. This is true even if the updates are being externally
generated by another PFI. The output is an active low pulse with a pulse
width of 300 to 350 ns. This output is set to tri-state at startup.
Figures 4-26 and 4-27 show the input and output timing requirements for
the UPDATE* signal.
Figure 4-26. UPDATE* Input Signal Timing
Figure 4-27. 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 device 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.
Rising-Edge
Polarity
Falling-Edge
Polarity
t
w
= 10 ns minimum
t
w
t
w
= 300 to 350 ns
t
w
UM.book Page 33 Monday, May 14, 2001 10:32 AM