Tandy 2000 Service Manual page 14

Tandy@
Model
2000
Service
l-lanual
Also available as an
enhancement
of the black
and
white
monitor is a e/w graphics option
board (26-5L4O).
This
feature
al-J-ows
the presentation of graphic material
on
the
display
monitor
with individually
addressed
pixels.
A
color
monitor (26-5LI2) is available
which
utilizes a 14"
color
screen, a color graphics option (25-26-5141),
and
the
B/w
graphics
option to provide 8 color presentations at
one time
on
the
monitor.
Standard
internal
RAIvI
memory
consists of a plug-in
128K
board. This
board
plugs into the
Main
Logic
board
and
may
be
expanded
to provide
256K
of
RAM
with
an
additional
128K
board
(26-5160). In addition to this
memory
up
to
two
26-5L6L
boards (considered
external since they
are
accessible
from
the outside of the ltain Unit)
may
be
plugged
into the
motherboard
located at the rear of the
Main
Unit.
These
boards
are populated
with
128K
of
RAM
and
may
be
further
expanded
to
255K
each
with additional
54K
x I
RAM
chips (option 26-5L62).
When
all of
these boards
are
incorporated
into the
system,
they provide a total
RAIII
capacity of
784K
bytes of
memory.
The
TV/Joystick
Board
allows
attachment
of user-supplied
Joy
Sticks or paddles.
Two
joysticks
may
be attached
to
t,he
ltodel
2000
for
use
with
games
available in the
software
library of the
Model
2000.
The
I'1ouse,/C1ock
option
board
allows input with
an external
input
device
called a
"mouse"
as
well
as
providing the
time
of
day
with a battery
backup
clock,/calendar
chip.
The
mouse
is a unit
which
is rolled along a desk top
and encodes
a
digital input to the
computer.
A
built-in
RS-232 asynchronous
interface
allows
communication
with external
devices through
the
use
of
a
modem. These
devices
may
be
local or remote, using
a
telephone
line to co'm0unicate.
The
option
supports 50 to
9500
BPS
transmission
speeds and
utilizes a 25-pin
D
connector located on
the rear panel of the
Main
Unit.
-5-