Philips PCL304 - Introduction; Main Board

2.
GENERAL
SYSTEM
DESCRIPTION
2.1 Introduction
The
system
features
a
16
Mhz
80C386
based
PC/AT
com-
patible
main
board
placed
in
a
high
performance
small
size
laptop
chassis.
The basic system includes:
+ + £ © ££ & £
Main board assembly,.
Power board assembly,
Keyboard assembly,
Floppy disk drive,
Hard disk drive,
LCD assembly,
Main battery
Adapter.
2-1
2.2. Main board
The
main
board
compromises
the
following
>
gic:
*
CPU
(Central
Processing
Unit)
The
80C386Sx
is
used
for
the
system
CPU
(3
2
bit
micro-
processor)
and
the
CPU
clock
frequency
canke
swit-
ched
for
low
speed
operation
from
the
standard
16
Mhz
to
8
Mhz.
System logic (HT-21)
The
HT-21
performs
CPU
and
peripheral
supRort
func-
tions
including
that
of
DMA
Controllers,
a
Memory
map-
per,
Timers,
Counters,
Interupt
controllers,
aus
control-
ler
and
their
supporting
circuitry.
This
chip
also
includes
address
buffers,
data
tranceivers,
memory
drivers,
parity
checking
and
supporiing
circuitry.
An
asynchronous
AT
Bus
clock
allows
for
aconstant
8
Mhz
clock
rate.
ROM (Read Only Memory)
The
ROM
BIOS
consists
of
one
128
x
8
bit
EPROM
mo-
dule.
RAM (Random Access Memory)
The
1
MB
on
board
standard
RAM
is
factory
installed.
Real Time Clock Generator (DS-1287)
The
DS-1287
is
a
complete
subsystem
in
atypical
appli-
cation.
A
lithium
energy
source,
quartz
crystal
and
write-
protection
circuitry
are
contained
within
the
24-pin
dual
in-
line
package.
The
functions
include
a
nonvolatile
time-of-day
clock,
an
alarm,
a
one
hundred-year
calender,
programmable
inter-
rupt,
square
wave
generator,
and
50
bytes
of
nonvolatile
static
RAM.
The
Real
Time
Clock
plus
RAM
is
distinctive
in
that
time-
of-day
and
memory
are
maintained
even
in
the
absence
of
power.
Keyboard Controller & Encoder (8042 & 80C51)
Controller is the 8042 and encoder is 80051
LCD/CRT Controller Interface (CL-GD 610, 620)
The
CL-GD610
graphics/attributes
chip
and
the
CL-
GD620
Sequencer/CRT
controller
chip
are
hardware
compatible
with
the
IBM
VGA,
EGA,
CGA
and
MDA
stan-
dard.
Parallel Port & Serial Port interface (82C601)
The
82C601
chip
features
drivers
for
the
output
buffers,
such
as
the
host
data
bus
and
parallel
port
data
bus.
It
in-
corporates
two
16450
compatible
UARTs,
one
enhanced
parallel
port
and
various
chip
selects.
Floppy disk interface (8473)
The
floppy
disk
controller
provided
with
two
floppy
disk
drivers
through
an
internal
FDD
interface
ard
the
other
external
FDD
interface.
The
system
has
a
built-in
hard
disk
with
a
capacity
of
40
Megabytes
(MB),
average
access
time
is
29
ms.
CS 55 798