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Chapter 4 Signal Connections
PCI-6110E/6111E User Manual 4-22
©
National Instruments Corporation
STARTSCAN Signal
Any PFI pin can externally input the STARTSCAN signal, which is
available as an output on the PFI7/STARTSCAN pin. Refer to
Figures 4-8 and 4-9 for the relationship of STARTSCAN to the DAQ
sequence.
As an input, the STARTSCAN signal 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 the STARTSCAN signal initiates a
scan. The sample interval counter starts if you select internally
triggered CONVERT*.
As an output, the STARTSCAN signal reflects the actual start pulse that
initiates a scan. This is true even if the starts are being externally
triggered by another PFI. 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 will be deasserted t
off
after the last
conversion in the scan is initiated. This output is set to tri-state at
startup.
Figures 4-16 and 4-17 show the input and output timing requirements
for the STARTSCAN signal.
Figure 4-16.
STARTSCAN Input Signal Timing
Rising-edge
polarity
Falling-edge
polarity
t
w
t
w
= 10 ns minimum
PCI_E.book Page 22 Thursday, June 25, 1998 12:55 PM