EasyManua.ls Logo

Texas Instruments 99/4A - Page 19

Texas Instruments 99/4A
146 pages
Save Page as PDF
Print Icon
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Loading...
The
purpose
and
composition
of
these
functional
sections
is
to
provide
an
overview
of
the
99/4A
system
with
a
detailed
description
in
the
succeeding
paragraphs.
•
The
clock
generator/driver
provides
4
non-overlapping
clock
signals
for
the
TMS
9900
microprocessor
and
also
internal
latch
which
is
used
on
the
reset
circuitry.
•
The
microprocessor
unit
with
the
TMS
9900
handles
all
the
processing
as
required
by
the
on
board
software
as
well
as
the
off
board
software
(DSP's
and
command
modules),
interrupts,
and
power
up
i
n
i
t
i
al
i
z
at
i
on
.
•
The
memory
address/decode
logic
provides
enabling
signals
to
the
various
RAM's,
ROM^s,
GROM's
and
interface
circuit.
•
System
RAM
consists
of
256
bytes
static
RAM
used
as
a
scratch
pad
memory
for
all
system
operations.
The
system
ROM
consists
of
8K
bytes
of
the
following
system
programs.
-
The
GRL
interpreter.
-
Floating
point
routines.
-
String
conversation
routines.
-
Cassette
interfacing
and
I/O
programs.
-
Basic
programs.
•
The
16
to
8
bit
interfacing
circuit
enable
the
99/4
to
access
8
bit
devices
by
multiplexing
and
demultiplexing
the
16
bit
data
bus
of
the
TMS
9900.
Timing
and
control
logic
provides
the
timing
and
enables
signals
for
the
16
to
8
bit
interfacing
circuit.
It
also
handles
the
READY
and
WE
signal
for
memory
operations.
The
TMS
9901
1/0
controller
is
the
interface
used
by
the
keyboard
scanning
circuit
and
the
cassette
interfacing
circuit.
It
also
handles
interrupts
and
has
an
on-chip
timer.
GROM
memory
consists
of
18K
bytes
of
graphics
program.
(Graphics
is
the
intermediate
language
used
in
the
99/4A)
It
contains
the^
following
system
routines:
GROM
0
:
-
Monitor
routines
-
First
part
of
the
equation
calculator.
-
The
cassette^device
subroutine
contain
ROM.
GROM
1
:
-
The
editor
-
The
prescan
routine
for
basic.
-
The
first
part
of
the
basic
executing
program.
GROM
2
:
-
The
file
management
programs.
-
The
second
part
of
the
basic
executing
program.
-
The
second
part
of
the
equation
calculator.
GROM
memory
is
expandable
up
to
a
limit
of
48K
through
the
grom
1/0
port.
The
GROM
port
enables
the
user
to
run
preprogrammed
software
in
up
to
5
GROM
’
s
in
a
software
module.
This
module
may
also
contain
in
ROM
processing
for
generating
the
composite
video
signal.
A
part
of
the
16K
byte
uses
RAM
during
the
power-up
sequence.
11

Related product manuals