Tektronix 11A52 Service Manual page 22

Theory of Operation
The Analog Control Voltage System (ACVS) provides DC voltage outputs that are used to set the Amplifier
offsets and variable gain control voltages. The processor stores the digital values of each of the ACVS voltage
levels in the 16 ACVS registers in the Housekeeper IC. The Housekeeper IC then sequentially updates each of
the outputs of the sample and hold modules through a digital-to-analog (D/ A) converter. The ACVS updates
continuously and requires minimal attention from the MPV.
Amplifier channel switching operates in a like manner. The processor stores the channel switching parameters
in the Housekeeper IC Then the Housekeeper IC. sequentially turns any of the channels on or off, under control
of the oscilloscope's channel switch sequencing signals. The Amplifier's step gain and bandwidth settings are
controlled via an extension of the MPU's external data bus that is provided by the Housekeeper IC.
The
MPV
uses an analog-to-digital (A/D) converter to read the value of the Overload Sense and Probe Data
lines. The A/D converter is also used for self-testing the plug-in.
The Front-Panel Pushbuttons are read by the MPV. When a button is pressed the MPV tells the oscilloscope
that a front-panel button was pushed. The oscilloscope then tells the plug-in what action to take (e.g., display
a channel and turn on the front-panel LED of the selected channel).
2-2 11A52 Extended Service Manual
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