
Chapter 4 Connecting Signals
© National Instruments Corporation 4-29 NI PCI-6110/6111 User Manual
UPDATE* SignalAny PFI pin can externally input the UPDATE* signal, which is available 
as an output on the PFI5/UPDATE* pin. 
As an input, UPDATE* is configured in the edge-detection mode. You can 
select any PFI pin as the source for UPDATE* and configure the polarity 
selection for either rising or falling edge. The selected edge of UPDATE* 
updates the outputs of the DACs. In order to use UPDATE*, you must set 
the DACs to posted-update mode.
As an output, UPDATE* 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 50 to 75ns. 
This output is set to high-impedance at startup.
Figures4-24 and 4-25 show the timing requirements for UPDATE*. 
Figure 4-24.  UPDATE* Input Signal Timing
Figure 4-25.  UPDATE* Output Signal Timing
The DACs are updated within 100ns of the leading edge. Separate the 
UPDATE* pulses with enough time that new data can be written to the 
DAC latches.
Rising-Edge
Polarity
Falling-Edge
Polarity
tw = 10 ns minimum
tw
tw = 50 to 75 ns
tw