PART ONE: INTRODUCTION
TO
THE
2495
OVERVIEW
The
Intecolor
2405
is
a
data
terminal,
a device which an operator uses
to
communicate with a host computer and
to
control
auxiliary
equipment
like
printers
and
plotters.
Though
they
are
physically
unified,
the
2405's components have
two
logically
distinct
functions.
The
keyboard
acts
as
an
input
device
for
the
host
computer,
while
the
display
screen
acts
as
an output device
for
the
host
computer.
These two
devices
can
function
in
a
simultaneous
and
independent
fashion.
Data can be
transmitted
from
the
keyboard
to
the
host
while
different
data
are
transmitted
fram
the
host
to
the
display.
This
type
of
operation
is
called
full
duplex.
The 2405
belongs
among
those
terminals
which
are
popularly
characterized
as
"intelligent"
because they have camputing
capabilities
of
their
own. These
capabilities
are
provided by
microelectronic
devices,
in
particula~
by
large
scal~
integrated
circuits
which
function
as
processors
and
memor1es.
In
general,
the
presence
of
such
capabilities
at
the
terminal
is
doubly advantageous:
first,
because
the
host's
workload can be
minimized
(especially
important
in
time-sharing
situations);
second,
because
host
programming can be considerably
simplified.
The
2405's
computing
capabilities
allow
it
to
respond
to
commands
which
are
very
simple
in
form,
yet
require
very
complex
operations
for
their
execution.
The
operations
of
which
the
terminal
is
capable include
all
those
needed
to
construct
multicolored
displays
of
text
and/or graphs
from
data
supplied
according
to
either
of
two
protocols.
These
protocols
include
the
device
independent
and otherwise very
flexible
ANSI
Standard
X3.64
protocol,
and
the
widely used
DEC
VT52
protocol.
The
2405's
main
functional
elements
are
represented
in
the
diagram
on
the
next
page
(Figure
1.1).
Data
enter
and leave
the
terminal
in
serial
form
through
two
bidirectional
ports.
One
of
these
ports
is
used
for
the
keyboard and
for
a
printer.
The
other
is-used
for
the
host.
Within
the
terminal,
data
are
handled
eight
bits
in
parallel
by
a
microprocessor.
Associated
with
the
processor
is
a
read-only
program
memory
and a
read/write
Setup
memory, which
stores
the
values
defining
terminal
operating
conditions
such
as
baud
rate,
type
of
parity,
etc.
This
Copyright
(C)
1983
-1.1-
by
Inteco1or
Corporation
