Chapter 8: Theory of Operation
Block-Level Theory
8–5
Moth
erboard
The motherboard provides all system control and interface functions for the oscilloscope. It
contains a CPU, ROM, RAM, keyboard and mouse interfaces, serial and parallel interfaces,
CDROM, hard and floppy disk drive interfaces, and PCI (Peripheral Component Interconnect)
buses.
Display Board
The Display Board controls the flat-panel display monitor. There are two major video paths on
this board. The first is used by the system controller on the motherboard to draw all general
display elements, including the grid, status indicators, and toolbars and menus for the graphical
interface. This is handled through a standard VGA chip, BIOS, and Graphics Board, similar to a
standard PC VGA interface. The other path is the video input from the oscilloscope interface
board, which is multiplexed with the main video to produce the video signals for the flat-panel
display. The video from the oscilloscope graphics board is the waveform display data.
Probe Power and Control
The Probe Power and Control board provides filtered, regulated power to the front-panel
AutoProbe interface. It also provides serial communications capability, offset and probe
detection and identification circuitry. All of these are interfaced to the probe through the
conductive pads surrounding the BNCs. Using the facilities of this board, the Autoprobe interface
can supply power for active probes, notify the oscilloscope operating system when a probe is
connected or disconnected, identify the probe type to the oscilloscope operating system for
automatic configuration, and communicate with the probe to support advanced probe
functionality.
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