Chapter4 SignalConnections
6023E/6024E/6025EUser Manual 4-40 ni.com
SISOURCE Signal
Any PFIpin can externally input the SISOU RCEsignal, w hich is not
available as an output on the I/O connector. The onboard scan interval
counteruses the SISOURCE signal as a clo ck to time the generation of the
STARTSCAN signal. You must configure the PFI pin you select as the
sourcefor the SISOU RCE signal in the level-detection mode. You can
configure the polarity selection for the PFI pin for either active high or
active low.
Themaximum allowed frequency is 20 MHz, with a minimum pulse width
of 23 ns high or low.There is no minimum frequency limitation.
Eitherthe 20 MHz or 100 kHz internal timebase generates the SISOURCE
signalunless you select some external source. Figure 4-29shows the timing
requirementsfor the SISOURCE signal.
Figure4-29. SISOURCESignal Timing
Waveform Generation Timing Connections
The analog group defined for your device is controlled by WFTRIG,
UPDATE*,an d UISOURCE.
WFTRIGSignal
AnyPFI pin can externally input the WFTRIG signal, which is available as
an output on the PFI6/WFTRIG pin.
Asan input, the WFTRIG signal is configured in the edge-det ection mode.
Youcan select any PFI pin as the source for WFTRIG and configure the
polarityselection f or either rising or falling edge. The selected edge of the
WFTRIGsignal starts the waveform generation for the DACs. The update
interval(UI) counter is started if you select internally generated UPDATE*.
tp
twtw
tp
tw
=50 ns minimum
=23 ns minimum