Chapter 4
Connecting the Signals
4-30
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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 4-15
and 4-16 for the relationship of STARTSCAN to the sequence.
As an input, STARTSCAN is configured in 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 SI2 counter starts if you select an
internally triggered CONVERT*.
As an output, STARTSCAN reflects the actual start pulse that initiates
a scan, even if the starts are externally triggered by another PFI. You have
two output options. The first option is an active high pulse with a pulse
width of 50 to 100 ns, which indicates the start of the scan. The second
option 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 4-21 and 4-22 show the input and output timing requirements
for STARTSCAN.
Figure 4-21.
STARTSCAN Input Signal Timing
Rising-Edge
Polarity
Falling-Edge
Polarity
t
w
= 10 ns minimum
t
w
