TDS 310, TDS 320 & TDS 350 Instruction Manual
51
Theory of Operation
This section describes the electrical operation of the TDS 310, TDS 320, and
TDS 350 to the module level.
This manual refers to digital logic circuits with standard logic symbols and
terms. Unless otherwise stated, all logic functions are described using the
positive logic convention: the more positive of the two logic levels is the high
(1) state andthe more negative level is the low (0) state. Signal states may
also be described as true" meaning their active state or false" meaning their
nonactive state. The specific voltages that constitute a high or low state vary
among the electronic devices.
Activelow signals are indicated by a tilde (~) prefixed to the signal name
(~RESET). Signal names are considered to be either activehigh, activelow,
or to have both activehigh andactivelow states.
This overview describes the basic operation of each functional circuit block
as shown in Figure 51.
Input Signal Path
A signal enters the oscilloscope through a probe connectedto a BNC on the
A1 Main Board.
Attenuators
Circuitry in the attenuator selects the input coupling and
attenuation factor. The processor system controls the attenuators with a serial
interface.
Probe Coding Interface
The probe coding interface signals pass
through the Main Boardto the A62 Front Panel, which senses them.
Acquisition System
The acquisition system amplifies the input signals,
samples them, converts them to digital signals, and controls the acquisition
process under direction of the processor system. The acquisition system
includes the trigger, acquisition timing, and acquisition mode generation and
control circuitry.
Processor System
The processor system contains a 68331 micropro
cessor that controls the entire instrument. The processor passes waveforms
andtext on to the display system. The Main Boardcontains both the proces
sor and display systems, in addition to the firmware ROMs.
Logic Conventions
Module Overview
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