National Instruments ni 6115-6120 User Manual

Any PFI pin can receive as an input the STARTSCAN signal, which is 
available as an output on the PFI7/STARTSCAN pin. Refer to Figures 4-18 
and 4-19 for the relationship of STARTSCAN to the DAQ sequence.

As an input, STARTSCAN is configured in the edge-detection mode. You 
can select any PFI pin as the source for STARTSCAN and configure the 
polarity selection for either rising or falling edge. The selected edge of 
STARTSCAN initiates a scan. The sample interval counter starts if you 
select internally triggered CONVERT*.

As an output, STARTSCAN reflects the actual start pulse that initiates a 
scan even if another PFI is externally triggering the starts. You have two 
output options. The first is an active high pulse with a pulse width of 25 to 
50 ns, which indicates the start of the scan. The second action is an active 
high pulse that terminates at the start of the last conversion in the scan, 
which indicates a scan in progress. STARTSCAN is deasserted t

off

 after the 

last conversion in the scan is initiated. This output is set to high-impedance 
at startup.

Figures 4-18 and 4-19 show the timing requirements for STARTSCAN.

 

Figure 4-18.  STARTSCAN Input Signal Timing

Rising-Edge

Polarity

Falling-Edge

Polarity

t

w

 = 10 ns minimum

t

w