HP 1660CS-Series User Manual page 282

The Analyzer Hardware
Oscilloscope board theory
clock derived from the sample rate oscillator. When the interpolator
indicates the stretch is complete, the counter is stopped. The count
represents, with much higher accuracy, the time between the trigger and the
first sample clock. The count is stored and used to place the recently
acquired data in relationship with previous data.
AC Cal The AC Cal is a multiplexer circuit that can provide several
signals to the Probe Compensation/AC Calibrator output on the rear
panel. The signal provided depends on the mode of the instrument. It
can be either a probe compensation signal, a pulse representing the
trigger event, signals used for self-calibration, or the 100 MHz reference
oscillator when sample period is 1 ns.
DC Cal The DC Cal output, a rear panel signal, is used for
self-calibration. It is one output from the 16-channel DAC.
Digital Interface The Digital Interface provides control and interface
between the system control and digital functions in the acquisition
circuitry.
Analog Interface The Analog Interface provides control of analog
functions in the acquisition circuitry. It is primarily a 16-channel DAC
with an accurate reference and filters on the outputs. It controls channel
offsets and trigger levels, and provides the DC Cal output.
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