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SECTION
I.
GENERAL
1.1
Introduction
The Color Computer
3
is a
refined
version
of
Tandy's popular Color
Computer
2.
It
is
designed
to
provide
the
same reliable
operation
as its
predecessor, but
it
incorporates
the
latest
in
electronic technology.
Figure
1-1
shows a typical
installation
of
the
Color Computer
3.
The Color Computer
3
contains
an
internal BASIC program
in
ROM which
is
accessed when
the
unit
is
powered
up.
Other program modules/cartridges
may
be
inserted into
the
receptacle
on
the
right side of
the unit. An
optional Multi-pak Interface module
allows
up to four
program paks
to be
installed at
the
same time,
with
selection
of the specific
module
active
at
any one time
selected
either
by
software
or
by
a
switch
on
the
Multi-pak Interface. Additional
peripheral devices, such
as
an
external disk
drive,
may
be
added
to
the
Color Computer
3
for
additional
memory storage
and retrieval.
All input and output ports
for the
Color Computer
3,
with
the
exception
of
the
program module/cartridge
slot
and
the
RGB monitor output
(for
CM-8), are located on
the
rear panel
of the unit.
These include
the
joystick
input ports (right and
left), Serial
I/O,
Cassette
I/O,
TV
output jack (for standard color
television
set and
composite
monitor), POWER ON/OFF switch and
RESET switch. A recessed channel
switch (for selecting either channel
on
the
TV
-
3/4
for
NTSC and
1/2
for
PAL version)
is
also located on
the
rear panel
of the
unit.
1.2
System Description
The
primary functions
of the Color
Computer
3
are performed by four
Large Scale Integration
(LSI) chips,
plus
Random Access Memory
(RAM) and
Read Only Memory (ROM). These four
chips are labeled on
the
block
diagram
as CPU,
ACVC
and two PIAs.
With only these
four chips, plus
Random Access Memory
(RAM), Read
Only
Memory
(ROM) and
a
power supply,
the
Color Computer
3
will operate
and
provide video output
(RF,
Composite,
Analog
RGB). However,
to
allow
communication with
the
outside world,
I/O interfaces
must
be added.
The
main component
of any
computer
system
is
the
Central Processing Unit
(CPU, IC1).
It
is
the
function of
the
CPU to provide or request data and
select
the
proper address
for this
data. In addition, the CPU
is
capable
of
performing
a
limited
set of
mathematical
and logical
operations
on the data.
ROM
(IC2) has the
function of
providing
the
CPU with
a
predefined
set of
instructions. Without
ROM, the
CPU would run wild and randomly
execute instructions.
In
normal
operation,
the
CPU jumps
to
the
start
address
in
ROM, after the reset
switch has been pressed, and then
performs
the
reset program
to set up
all of the
programmable devices.
Following
this, the
BASIC interpreter
residing
in
ROM
is
in
control of
the
CPU.
Note:
Before installing any
peripheral device, always remember
to
unplug
the
Color Computer's power
cord. This
will prevent damage
to
the
device
or to the
Color Computer
3.
-5-
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