Theory of Operation
371B Service Manual
3-7
Microprocessor.
The 68000 is a 16-data bit, 23-address bit microprocessor. The
input and output signals can be grouped in eight categories. The following
paragraphs describe each group and the signals in that group.
The A2 CPU board also contains the memory circuits which consist of the ROM,
RAM, battery backup, address selector, and buffers.
The A/D control and step generator circuit, located on the A3 A/D (analog to
digital) board, consists of an acquisition and step generator control circuit, pulse
generator circuit, step generator circuit, and control latch and decoder circuit.
These circuits generate a variety of signals for the step generator, and generate
pulse timing signals for the high-current mode.
The collector supply generator circuit, located on the A3 A/D board, consists of a
sine-square wave timing generator, sine-square wave generator, collector level
control circuit and high voltage sine-square wave attenuator circuit. These
circuits generate a sine-square wave synchronized to the line frequency, which is
the source of the collector signal in the high voltage mode, and DC signal which
is the source of the collector signal in high current mode.
The acquisition circuitry, located on the A3 A/D board, consists of an S/H
(sample and hold) and select circuit, A/D timing circuit, acquisition memory
control circuit, acquisition memory circuit and bus driver circuit.
These circuits perform A/D conversion of the HD and VD signals from the A5
Display Control board, write them into acquisition memory, and transfer data to
the CPU.
The display counter circuitry is located on the A4 Digital Display board. The
display counter circuit consists of the bus buffer, the 4.5 MHz oscillator, display
counter, address switch & CPU control, display RAM, bus transceiver, dot
cursor generator and character & latch controller.
These circuits determine if the CPU accesses the display RAM, or the display
counter reads out the display RAM contents to display them on the CRT. This
circuit also generates the necessary control signals for the display.
The display D/A converter circuitry is located on A4 Digital Display board. The
display D/A converter circuitry consists of the following circuits:
1. X data & attribute prefetch latch
2. X-Y data & attribute load latch
Memory
A/D Control and Setup
Generator Circuit
Collector Supply
Generator
Acquisition
Display Counter Circuit
Display D/A Converter
Circuit
Summary of Contents for 371B
Page 4: ......
Page 14: ...Service Safety Summary 371B Service Manual...
Page 18: ...Preface 371B Service Manual...
Page 21: ...Specifications...
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Page 24: ...Product Overview 371B Service Manual...
Page 38: ...Specifications 371B Service Manual...
Page 39: ...General Information...
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Page 58: ...General Information 371B Service Manual...
Page 59: ...Theory of Operation...
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Page 62: ...Theory of Operation 3 2 371B Service Manual Figure 3 1 371B Block Diagram...
Page 71: ...Maintenance...
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Page 101: ...Performance Verification...
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Page 220: ...Performance Verification 371B Service Manual...
Page 221: ...Options...
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Page 226: ...Options and Accessories 371B Service Manual...
Page 227: ...Electrical Parts List...
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Page 235: ...Diagrams...
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Page 279: ...9 29 371B Service Manual Figure 9 6 Front Porch...
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