User`s guide

Operation Theory
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4.6.1 DAQ timing signals
The user-controllable DAQ timing-signals contains: (Please refer to 4.1.3.1
for the internal timing signal definition)
1. TIMEBASE, providing TIMEBASE for all DAQ operations, which can
be from internal 40MHz oscillator, EXTTIMEBASE from I/O con-
nector or the SSI_TIMEBASE. Note that the frequency range of the
EXTTIMEBASE is 1MHz to 40MHz, and the EXTTIMEBASE 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-compatible and the minimum pulse width should be the pulse
width of the TIMEBASE to guarantee correct functionality.
4. ADCONV, the conversion signal to initiate a single conversion, which
can be derived from an 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(DAQ-2214), 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
description.
6. DAWR(DAQ-2214), the update signal to initiate a single D/A con-
version, 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.