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Model 4000C Instruction Manual
MAIN CHASSIS
The Main Chassis is a cabinet containing plug-in circuit boards, fixed interconnect boards,
cabling, and a power supply. Three of the plug-in circuit boards provide Test control and
operation functions. These boards are:
CPU/RAM Board
I/O (Input/Output) Board
Scanner Control Board
These three circuit boards are interconnected by an address bus, data bus, and control/timing
bus. Sixteen Scanner Boards, with 128 test points per board, provide a scan total of 2048 test
points in the main chassis. A Scanner Interconnect board provides electrical interface with
these 16 Scanner Boards. Additional Scanner Boards can be added in the optional Expansion
Chassis to increase total test capacity to 4096 points.
CPU/RAM Board
The CPU RAM Board provides control over the Dynamic Memory, I/O and Scanner Control
Boards through Address, Data, and Control busses. Key elements on the CPU/RAM Board
are a 6809 microprocessor, 128K of Dynamic RAM Memory, 2K of Static RAM, 24K bytes
of EPROM (erasable programmable read-only-memory), decode logic, and bus drivers.
I/O Board
The I/O Board serves as a traffic control between the CPU and the mode switches, display,
Printer and terminal port. Key elements of the I/O Board are decode and control logic, a
control head interface, dual baud rate generator, two ACIAs (asynchronous communications
interface adapter) and baud rate switches.
Scanner Control Board
The Scanner Control Board provides a control interface between the CPU and the Scanner
Boards in the Main Chassis. Key elements of the Scanner Control Board are a transmit point
control, received point control, continuity detect control, automatic scan circuit, and scan rate
clock.
CONTROL HEAD
The Control Head is connected to the Main Chassis by cable. Membrane switches (touch-
sensitive) provide for initiation or termination of operating modes; above each switch is an LED
indicator, which lights when its switch is active. A 32-character alphanumeric display provides
test condition and point-to-point identification. Also included on the Control Head are a
speaker, an EARPHONE jack, a PROBE receptacle for body conductance, and a VOLUME
control.
SYSTEM OVERVIEW
Page 4
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