Chapter 3
Connecting the Signals
©
National Instruments Corporation
3-35
DAQPad-MIO-16XE-50 User Manual
UPDATE* Signal
Any PFI signal can externally input UPDATE*, which is available as an
output on the PFI5/UPDATE* screw terminal.
As an input, the UPDATE* signal is configured in the edge-detection mode.
You can select any PFI signal as the source for UPDATE* and configure the
polarity selection for either rising or falling edge. The selected edge of
the UPDATE* signal updates the outputs of the DACs. In order to use
UPDATE*, you must set the DACs to posted-update mode.
As an output, the UPDATE* signal reflects the actual update pulse that is
connected to the DACs, 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 high-impedance at start up.
Figures 3-25 and 3-26 show the input and output timing requirements for
the UPDATE* signal.
Figure 3-25.
UPDATE* Input Signal Timing
Figure 3-26.
UPDATE* Output Signal Timing
The DACs are updated within 100 ns of the leading edge. Separate the
UPDATE* pulses with enough time so that new data can be written to
the DAC latches.
Rising-Edge
Polarity
Falling-Edge
Polarity
t
w
= 10 ns minimum
t
w
t
w
= 300 to 350 ns
t
w
UPDATE*
