Acer Extensa 450 Maintenance Manual

							4
Theory of Operation
4.1Introduction
This section describes the notebook theory of operation. 
4.2  Notebook Functional Description
Functionally, the notebook computer consists of the following major subsystems:
·Processor and Memory Subsystem
·I/O Subsystem
·Video Subsystem
·Hard Disk Subsystem
·Floppy Disk Subsystem
·PCMCIA Subsystem
·Serial Infrared Subsystem
·Power Subsystem
A functional block diagram of the Extensa Notebook is shown in Figure 4-1.
4.2.1 Processor/Memory Subsystems 
The Processor function, housed on the Main Board, is implemented with a 75mhz
IntelDX4 Processor. The processor operates in conjunction with RAM and ROM
Memory on the Memory Board and other control logic on the Main Board to process
software instructions (BIOS, Windows 95, and Applications). 
Primary control for the Processor/Memory subsystem is implemented with the
M1429L PC/AT Chipset. Address buffering and real time clock function is
implemented with an M1441L.
The memory subsystem, implemented on the Memory Board and optional Dual
Inline Memory Modules, provides 4MB (expandable to 32 MB) of fast DRAM
memory, 128 bytes of CMOS RAM (battery backed up) and 256 KB of Flash ROM for
system and video BIOS storage. Tables 4-1 through 4-3 contain the Notebook I/O
address map, DMA channel assignments and IRQ interrupt level assignments
respectively.
   
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							Figure 4-1   Notebook Functional Block Diagram
   
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Table 4-1   Extensa Series I/O Address Map
Address Range Device
000-00F DMA Controller 1 
020-021 Interrupt Controller -1
022-023 M1429 Registers
040-043 T imer 1
060-06E Keyboard Controller 8742 Chip Select
070-071 Real Time Clock and NMI Mask
080-08F DMA Page Register
0A0-0A1 Interrupt Controller 2
0C0-0DF DMA Controller -2
1F0-1F7 Hard Disk Select
178,,17A 6377 Registers
1F0-1F7 Hard Disk Select
3F6,,3F7, 
278-27F Parallel Port 3
35F, 36F Special I/O Ports
378,,37A Parallel Port 2
3BC-3BE Parallel Port 1
3C0-3C5
3C6-3C9 Video DAC
3C0-3CF Enhanced Graphics Display
3D0-3DF Color Graphics Adapter
3E0-3E1 PCMCIA Controller
3F0-3F7 Floppy Disk Controller
3F8-3FF Serial Port 1
 
   
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							Table 4-2  DMA Channels
Controller Channel Address Function
1 0 0087 Spare
1 1 0083 Spare
1 2 0081 Diskette
1 3 0082 Spare
2 4 Cascade Cascade
2 5 008B Spare
2 6 0089 Spare
2 7 008A Spare
Table 4-3  IRQ Interrupt Levels
Priority Interrupt
NumberInterrupt Source
1 SMI Power management unit
2  NMI Parity Error Detected,,I/O Channel Error
3 IRQ0 Interval Timer,,Counter 0 Output
4 IRQ1 Keyboard
IRQ 2 Interrupt from controller 2 (cascade)
5 IRQ8 Real Time Clock
6 IRQ 9 Cascaded to INT 0AH (IRQ 2)
7 IRQ10 Reserved
8IRQ
11,Reserved
9IRQ 12,PS/2 Mouse 
10 IRQ13 INT from Coprocessor
11 IRQ14 Hard Disk Controller
12 IRQ15 Reserved
13 IRQ3 Serial Comm
Port 2
14 IRQ4 Serial Comm Port 1
15 IRQ5 Reserved
16 IRQ6 Diskette Controller
17 IRQ7 Parallel Port
   
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							nNote:  A PCMCIA card can use IRQ 3, 4, 5, 7, 9 and 11 as long as it does not
conflict with the interrupt address of any other device.
4.2.2   I/O Subsystem
The I/O subsystem, implemented with an NS87334 VJG Super I/O Controller Chip,
provides for such functions as internal Hard Drive control, floppy drive control,
serial and parallel ports and support for the Serial Infrared port. The Super I/O
Controller includes the following features: .
·100 percent compatible with ISA, EISA, and Micro-channel architectures
· Built-in  Floppy Disk Controller
·Software compatible with the DP8473, the 765A and N82077
·16-byte FIFO (default disabled)
·Burst and Non-burst modes
·Perpendicular Recording drive support
·New high-performance internal digital data separator (no external
filter components required)
·Low-power CMOS with enhanced power -down mode
·Automatic media-sense support
·Two UARTS
·Software compatible with the PC16550A and PC16450
·MIDI compatible
·Infrared support on UAR T2 (IrDA-compliant)
·Bidirectional Parallel Port
· Enhanced Paralle Port (EPP) compatible
·Extended Capabilities Port (ECP) compatible, including level 2
support
·Bidirectional under either software or hardware control
·Compatbile with ISA, EISA, and Micro Channel architectures
·Ability to multiplex FDC signals on parallel port pins for external
FDD
   
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							·Includes protection circuit against damage caused when printer is
powered up, or operated at higher voltages
· Integral IDE controller
·Provides a complete IDE interface with DMA control (except for
optional buffers)
·Integral address decoder- provides selection of all primary and secondary ISA
addresses including COM1-4 and LPT1-3.
·Enhanced Power Management Function
·Special configuration registers for power down
·Enhanced programmable power -down and wake-up modes
·Auto power -down and wake-up modes
·3 special pins for power management
·Typical current consumption during power -down is less than 10A
4.2.3   Video Subsystem
The video subsystem, implemented on the Main Board and on the LCD Display
Unit, displays text, graphics and drives an external VGA port. The video subsystem
is implemented with a Cirrus Logic 6245 high performance flat panel/R T VGA
controller and supporting logic and video RAM (512KB).
The major features of the VGA controller include: 
·Highly integrated design (flat panel / CRT VGA controller, RAMDAC, clock
synthesizer)
·Multiple Bus Architecture Integrated Interface
· Local Bus (32-bit CPU Direct and VL)
· EISA/ISA (PC/AT) 16-bit Bus
·Advanced frame buffer architecture uses available display memory, maximizing
integration and minimizing chip count
·Integrated programmable linear address feature accelerates GUI performance
·High performance resulting from zero wait state writes (write buffer) and
minimum wait state reads (internal asynchronous FIFO design)
·Supports panel resolutions up to 1280 x 1024 resolution including 800x600
and 1024x768
· SMARTMAP intelligent color to gray scale conversion enhances text legibility
· Text enhancement feature improves white text contrast on flat panel displays
· Fully Compatible with IBM VGA
   
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							4.2.3.1   External VGA Drive Capability
On the Extensa 450, the external VGA port is provided by the port adaptor fixture
in the form of a 15-pin, female, D-type connector which can be used to drive an
external CR T (standard VGA modes with resolutions of 800 X 600 X 256, or 640 X
480 X 256 ).
4.2.4   Hard Disk Subsystem
The Hard Disk Subsystem, controlled by the IDE interface compatible NS87334
VJG Super I/O Controller on  the Main Board, provides disk storage for all system
software and user files. Initially, the 450 Series Notebooks are equipped with a 340
Million Byte hard drive. However, the onboard controller can support high capacity
drives.
During the manufacturing process, Texas Instruments formats the hard disk and
then loads all supplied software including Windows 95.
cCaution: Formatting the disk drive erases any data that may be stored
on the disk. Therefore do not attempt a format of the hard disk unless
the computer self-test and diagnostics confirm that the disk has not
been formatted.
A Hard Drive activity LED is located along the front edge of the notebook. This LED
lights during hard driver read/write accesses. 
cCaution:  The notebook should not be moved when the HDD LED is lit to
prevent accidental damage to the hard drive. 
4.2.5  Floppy Diskette Drive Subsystem
The Floppy Diskette Drive Subsystem consists of a Floppy Controller and the Floppy
Diskette Drive. The Floppy Diskette Drive can read/write standard 3.5-inch
minidiskettes.
4.2.6 PCMCIA Subsystem
The notebook is equipped with an on-board PCMCIA host adapter (CL-PD6722
PCMCIA Controller) and sockets to support one Type I or Type II option or a Type III
option if the Floppy Drive is removed from the unit. The PCMCIA Controller has the
following features: 
· Single-chip PCMCIA host adapters
   
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							· Direct connection to ISA (PC AT) Bus
· Direct connection to PCMCIA 2.0 Bus
· PCMCIA 2.0- and JEIDA 4.1-compliant
· 82365SL-compatible register set, ExCA-compatible
· Automatic Low-power Dynamic Mode for lowest power consumption
· Programmable Suspend Mode
· Five programmable memory windows per socket
· Two I/O windows per socket
· Programmable card access cycle timing
· 8- or 16-bit CPU interface
· 8- or 16-bit PCMCIA interface support
· ATA disk interface support
· Automatic flash memory timing support
· Easy host interface using ISA I/O addresses 03E0h, 03E1h
· Mixed-voltage (3.3V or 5V) operation
· Dual-socket-interface, 208-pin QFP
4.2.7 Power Subsystem
The Power Subsystem consists of the following major parts:
· Power Management (hardware and software components)
·AC Adapter
· Primary Battery Board
·Primary Battery Pack
·Secondary Battery Board
·Secondary Battery Pack
4.2.7.1  Power Management
The notebook is equipped with a power management function that minimizes
battery usage for prolonged battery operation and automatically recharges the
batteries when the notebook is used with an AC adapter. 
The power management modes and warnings include the following:
   
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							· LCD standby mode
·Hard disk standby mode
·System standby/suspend mode
·Battery-low warning
·Standby/suspend upon battery low
4.2.7.2   AC Adapter
The notebook uses an AC adapter with built in over voltage and short circuit
protection.
The adapter can with stand a continuous short-circuit to DC output without
damage to the notebook logic components. The adapter operates in shut down mode
shorting Vo trail and resets to the normal power mode after the fault condition is
removed. 
4.2.7.3   Primary Battery Pack
The Extensa Series Notebooks use the Duracell DR35 as the primary battery pack.
Specifications for the Primary Battery Pack are provided in Table 4-4.
Table 4-4 Primary Battery Pack Specifications
Function Specifications
Battery type NiMH (Nickel Metal-Hydride)
Cell structure 9 cells per pack (in series)
Nominal voltage 10.8 V
Cell energy capacity,
   Typical,
   Minimum2400 mAH
2500 mAH,
2330 mAH,
Nominal rated capacity 27 Watt-hours
Operating Temperature
_,
   Discharge,
   Charge-20 to 50°C (at 95%RH),
0 to 45°C (at 95%RH),
Charge and discharge
cycles500 (minimum),
Weight 470 grams
Battery discharge time 3 hours (with APM)
Battery charge time
   
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							4.2.7.4   Secondary Battery Pack
As an optional feature, the Floppy Drive can be removed from the notebook and a
Li-Ion (Lithium Ion) secondary battery pack can be installed in the same cavity to
provide additional battery operating time.
   
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