ACT apricot - System Board

SYSTEM UNIT
Connectors for the Keyboard, the Display Unit, the mains
input and other peripheral equipment are all located on the
rear panel of the Systems Unit. The connectors from left to
right when looking at the rear panel are as follows:
1. The Keyboard connector (9-pin female D-type).
2. A parallel
printer port (36-way female Centronics).
3.
An RS232C communications port (25-pin female
D-type).
4.
The Display Unit connector (9-pin male D-type).
Also
included on the rear panel is the mains switch and
the mains input fuse. The indicator on the switch is
illuminated when the Systems Unit is switched on.·
Two plastic expansion plates are located above the
Keyboard connector on the rear panel. These are removed to
allow external equipment to be connected to the expansion
boards
with a minimum of modification to the rear panel.
All
the processing circuitry is contained on a single
printed circuit board, the System Board, which fits
horizontaJly
into the base of the Systems Unit. Located
above
the System Board inside the Unit, is the Power Supply
Unit,
a loudspeaker and either one or two disk drives. The
cooling fan is attached to the inside of the rear panel.
SYSTEM BOARD
The System Board incorporates:
(a) The system processors.
(b) The Boot Proms.
(c) Thesystem memory (256 kbytes of dynamic RAM).
(d) TwoExpansion Slots.
(e) Circuitry for controlling the monochrome Display
Unit.
(f) A dual channel Serial Interface, one channel for
communicating with peripheral equipment via an
RS232C link, one channel for keyboard
communications.
(g) A Parallel Interface for connection to a printer.
(h) An interface for controlling the disk drivels).
(i) A sophisticated Sound Generator.