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Daq timing signals – ADLINK PXI-2006 User Manual

Page 73

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Operation Theory

63

DAQ timing signals

The user-controllable internal timing-signals contain: (Please refer
to Section 4.1 for the internal timing signal definition)

1. TIMEBASE, providing TIMEBASE for all DAQ opera-

tions, which could be from internal 40MHz oscillator,
EXTTIMEBASE from I/O connector or the
SSI_TIMEBASE. Note that the frequency range of the
EXTTIMEBASE is 1MHz to 40MHz, and the EXTTIME-
BASE should be TTL-compatible.

2. AD_TRIG, the trigger signal for the A/D operation, which

could come from external digital trigger, analog trigger,
internal software trigger and SSI_AD_TRIG. Refer to
Section 4.5 for detailed description.

3. SCAN_START, the signal to start a scan, which would

bring the following ADCONV signals for AD conversion,
and could come from the internal SI_counter, AFI[0] and
SSI_AD_START. This signal is synchronous to the
TIMEBASE. Note that the AFI[0] should be TTL-compat-
ible and the minimum pulse width should be the pulse
width of the TIMEBASE to guarantee correct functional-
ities.

4. ADCONV, the conversion signal to initiate a single con-

version, 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 effec-
tive conversion signal. Also note that the AFI[0] signal

AFI signals

Control DAQ-2000 by external timing signals

AI_Trig_Out, AO_Trig_Out

Control external circuitry or boards

Timing signal category

Corresponding functionality

Table 4-8: Summary of user-controllable timing signals and the

corresponding functionalities

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