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Operation Theory
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3. SCAN_START, the signal to start a scan, which would bring the fol-
lowing ADCONV signals for AD conversion, and could come from the
internal SI_counter, AFI[0] and SSI_AD_START. This signal is syn-
chronous to the TIMEBASE. Note that the AFI[0] should be
TTL-compatible and the minimum pulse width should be the pulse
width of the TIMEBASE to guarantee correct functionalities.
4. ADCONV, the conversion signal to initiate a single conversion, which
could be derived from internal counter, AFI[0] or SSI_ADCONV.
Note that this signal is edge-sensitive. When using AFI[0] as the
external ADCONV source, each
rising edge
of AFI[0] would bring an
effective conversion signal. Also note that the AFI[0] signal should be
TTL-compatible and the minimum pulse width is 20ns.
5. DA_TRIG, the trigger signal for the D/A operation, which could be
derived from external digital trigger, analog trigger, internal software
trigger and SSI_AD_TRIG. Refer to Section 4.5 for detailed de-
scription.
6. DAWR, the update signal to initiate a single D/A conversion, which
could be derived from internal counter, AFI[1] or SSI_DAWR. Note
that this signal is edge-sensitive. When using AFI[1] as the external
DAWR source, each
rising edge
of AFI[1] would bring an effective
update signal. Also note that the AFI[1] signal should be
TTL-compatible and the minimum pulse width is 20ns.
4.6.2
Auxiliary Function Inputs (AFI)
Users could use the AFI in applications that take advantage of external
circuitry to directly control the DAQ/PXI-2000 series cards. The AFI in-
cludes 2 categories of timing signals: one group is the dedicated input, and
the other is the multi-function input. Table 13 illustrates this categorization.
Table 13 summarizes the auxiliary function input signals and the corre-
sponding functionalities