Circuit Description
Analog Board
Processor System
3-4
A signal enters the oscilloscope through a probe connected to a BNC on the
A 1 Analog board.
Attenuators A 1
00
The attenuator hybrids AT401, AT402, AT450, and
AT451
, and the vertical
preamplifier
IC,
select the input coupling, attenuation factor, variable gain,
and the invert function. The processor system controls and calibrates the
attenuators.
Probe Coding Interface A 1
~
Probe coding interface signals pass through
the
A1
Analog board to the
A5
CPU
board and then to the
A4
Front Panel board. The probe interface
signals are digitized on the Front Panel board and communicated to the
processor system to control the instrument.
Analog Acquisition Hybrid A 1 0
The input signals are routed to the highly integrated analog acquisition
hybrid,
U405, which does the analog processing required to provide vertical,
horizontal, and
Z-axis signals to the
A3
Display Driver board. Under control
of the processor, the hybrid provides vertical signal processing, triggers,
sweeps, sequencing logic, and intensity control.
The processor board
is
a microcontroller design. Microcontroller
U201
is
the
core
of
the circuit, operating at 16 MHz. The primary function
of
the proces-
sor
is
to receive input from the front panel, display the readout, and control
the
A1
Analog board.
The processor board can be divided into five subsystems: the processor, the
ROM/RAM, the readout, the front-panel interface, and the analog board
interface. A description
of
each subsystem follows.
Processor Subsystem A5
<9
The processor subsystem consists
of
a 32-bit integrated microcontroller and
its supporting circuits.
It contains four peripheral modules; the
CPU,
a gener-
al-purpose timer (GPT), a queued serial module
(QSM), and a system in-
tegration module
(SIM).
The
CPU
is
based on the MC68020 instruction set and can utilize the exten-
sive software base for the Motorola
M68000 Family.
The GPT inputs are used for measuring the main and delay sweep gates,
as
well as the measurement latches. The outputs
of
the GPT are used for
loading or resetting various sections
of
the analog board.
Theory of Operation
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