Toshiba T-Series T4850CT User manual

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1.1 Features
The Toshiba T4850CT is one of the lightest and most advanced portable computers available.
Utilizing advanced technology and high-speed components, the T4850CT offers excellent
color display legibility, battery operation and IBM PC/AT compatibility. The T4850CT
system unit consists of the following features:
❑Microprocessor
The Intel DX4TM Processor (referred to as DX4 in this manual) operates at 75 MHz,
3.3 Volts.
❑Math co-processor
The math co-processor is stored in the DX4.
❑Cache memory
16 KB of cache memory is stored in the DX4.
❑Disk storage
The T4850CT has an internal 2.5-inch 500 or 810 MB HDD. The 3.5-inch FDD
supports 2 HD (1.44 MB) floppy disks and 2DD (720 KB) floppy disks.
❑Memory
The T4850CT comes standard with 8 MB of CMOS Random Access Memory (RAM)
3.3 Volts. This includes 640 KB of conventional memory and 7,360 KB of extended
memory which can be utilized as expanded memory compatible with the Lotus/Intel/
Microsoft Expanded Memory Specifications (LIM-EMS).
❑TFT color LCD
The T4850CT has a high-resolution 10.4-inch full-color, Thin Film Transistor (TFT)
color LCD that displays 640 x 480 pixels.
The internal display controller supports VGA functions on the internal display and
SVGA functions on an external display.
❑Keyboard
An easy-to-use 82/84-key enhanced keyboard with full-size keys and standard spacing
is compatible with IBM standard software.

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❑Batteries
The T4850CT has three different batteries: a main battery, backup battery, and a Real
Time Clock (RTC) battery.
❑Status indicator panel
The status indicator panel is a liquid crystal display (LCD) panel which includes a
battery charge indicator and 11 icons indicating the system status.
❑Memory card slot
The optional memory card slot enables you to install a Toshiba optional memory card.
❑Personal Computer Memory Card International Association (PCMCIA) card slot
The two PCMCIA slots enable you to install an MiNC Toshiba card modem or other
industry-standard PCMCIA release 2.0 card.
❑Expansion port
The unique 150-pin expansion port allows you to connect the T4850CT to a Desk
Station IV.
❑PRT/FDD port
The Centronics-compatible parallel interface port serves two purposes: the port can
be used to connect a Centronics-compatible printer or an external 5.25-inch floppy
disk drive.
❑RS-232-C port
The RS-232-C port is a 9-pin serial interface port.
❑Mouse port
The 6-pin mouse port on the back supports an IBM PS/2 mouse.
❑Keyboard port
The 6-pin keyboard port on the back supports an IBM PS/2 keyboard.
❑Microsoft BallPoint mouse V2.0 with QuickPort connection (BPQP2)
The T4850CT has one BPQP2 port on the right.

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❑RGB port
The 15-pin RGB port on the back supports an external video display.
❑Audio ports
•Headphone, standard 3.5 mm diameter miniature stereo jack with speaker shut-off
switch.
Use a headphone with an impedance of 16Ω.
•Microphone, standard 3.5 mm diameter miniature monaural jack.

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The T4850CT Personal Computer is shown in Figure 1-1, and its system configuration is
illustrated in Figure 1-2.
Figure 1-1 T4850CT personal computer
Figure 1-2 T4850CT system unit configuration

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1.2 System Unit Block Diagram
Figure 1-3 is a block diagram of the T4850CT system unit.
Figure 1-3 T4850CT system board block diagram

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The system board shown in Figure 1-3 is composed of the following major components:
❑A DX4-75 CPU, which incorporates a math co-processor and 16 KB cache memory.
❑The following memory components:
Standard RAM: 8 MB, 32-bit data width (70 ns)
Cache memory: 16 KB (inside the DX4-75 CPU)
System, Video, 128 KB (96 KB are used), 8-bit data width
BIOS: A 1-Mbit flash ROM is used (150 ns).
This ROM contains Initial Reliability Test (IRT), Basic Input/
Output System (BIOS), and video BIOS.
Video RAM: 1 MB, 16-bit data width.
Two 256K x 16 bit chips are used.
Memory card: 4, 8, or 16 MB memory card can be installed.
32-bit data width.
❑Super Integration (SI) T9901, which stores the following components:
•Two Direct Memory Access Controllers (DMAC): .82C37
•Two Programmable Interrupt Controllers (PIC): ..... 82C59
•One Programmable Interval Timer (PIT):................ 82C54
•One Floppy Disk Controller (FDC): ........................ TC8565
•One Serial Input/Output Controller (SIO): .............. TC8570
•One Variable Frequency Oscillator (VFO):.............. TC8568
•One I/O Controller
•One Printer Port Controller
•One Speaker Controller
❑Real Time Clock (RTC)
One T9934 chip is used (which has 128 of bytes memory). Fourteen bytes of memory
are used for the calendar and clock, and the remaining 114 bytes are used for system
configuration data.
❑Keyboard Controller (KBC)
One M37452M4 chip is used. This KBC includes the keyboard scan controller and
keyboard interface controller. The KBC controls the internal keyboard, external
keyboard port, PS/2 mouse port, and BPQP2 port.
❑VGA display controller: WD90C24A/A2 (208-pin) (3.3 volt operation)
This controller controls both internal and external VGA-compatible displays and
external SVGA-compatible displays with an Analog Digital Converter (DAC). The
controller can display data on the internal and external display simultaneously.

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❑Sound Controller
An AD1848 chip is used which controls the internal sound system.
❑The Clock Generator receives 14.31818 MHz (X1) and generates the following
frequencies:
•75 MHz for the CPU
•14.7456 MHz for the COM
•24 MHz for the FDC and VFO
•16 MHz is used for GA
•14.31818 MHz for WD90C24A (for VGA)
OSC (X3) generates 32.768 KHz for the RTC.
❑Gate Arrays
System Controller Gate Array
This gate array performs the following functions:
•CPU Controller
-SMI Controller
-CPU Clock Controller
•Memory Controller
-DRAM Controller
-Compatible Bus Interface Controller
•Bus Controller
-Compatible Bus Interface Controller
-Compatible Access Controller
-DMAC Controller
-I/O Controller
•Address Latch Controller
-32-Bit to 16-Bit Controller
-Address Latch
-DMA Address Generator
-Refresh Address Generator
•I/O Register
-Compatible I/O Port Register
-Saving the data of the Register (in resume) Controller
-Toshiba Special Register
•Processing Speed Controller
•Data Bus Transfer
•Data Latch
•Suspend/Resume Controller

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Sub LCD Controller Gate Array
This gate array performs the following functions:
•Status Indicator Panel Controller
-LCD Segment Flashing Controller
•Internal Communication Controller
-KBC/Power Supply Micro Processor/Main CPU Communication
Controller
-KBC/Power Supply Micro Processor Interrupt Controller
IC Card Controller Gate Array
This gate array performs the following functions:
•IC Card Controller
-PCMCIA IC Card Controller
-Toshiba Modem Card Controller
•EEPROM (for security) Controller
-KBC-Security-EEPROM Communication Controller
•Others
-KBC Communication Controller
-Disable the PRT/FDD Port, HDD Access Controller
-EEPROM (for BIOS) Access Mode Controller
-Sound System Access Controller

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1.3 3.5-inch Floppy Disk Drive
The T4850CT 3.5-inch Floppy Disk Drive (FDD) is a thin, high-performance reliable drive
that supports 720-KB (formatted) 2DD and 1.44-MB (formatted) 2HD 3.5-inch floppy disks.
The FDD is shown in Figure 1-4, and its specifications are listed in Table 1-1.
Figure 1-4 3.5-inch FDD
Table 1-1 3.5-inch FDD specifications
Item 2 MB mode 1 MB mode
Storage capacity (KB)
Unformatted 2,000 1,000
Formatted 1,311 737
Number of heads 2 2
Number of cylinders 80 80
Access time (ms)
Track to track 3 3
Average 181 181
Head settling time 15 15
Recording track density (tpi) 135 135
Data transfer rate (Kbps) 500 250
Rotation speed (rpm) 300 300
Recording method Modified Frequency Modulation (MFM)

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1.4 2.5-inch Hard Disk Drive
The Hard Disk Drive (HDD) is a random access, nonvolatile storage device. It has a non-
removable 2.5-inch magnetic disk and mini-winchester type magnetic heads.
The T4850CT supports a 500 MB and 810 MB HDDs.
The HDD is shown in Figure 1-5, and its specifications are listed in Table 1-2.
Figure 1-5 2.5-inch HDD
Table 1-2 2.5-inch HDD specifications
500 MB 810 MB
MK2428FC DHAA-2540 DVAA-2810
Physical specifications
Formatted capacity (MB) 524.0 528.0 810.0
Disks 4 2 3
Heads 8 4 6
Cylinders 1,920 1,024 1,571
Bytes per sector (bps) 512 512 512
Recording method 1-7RLL 1-7RLL 1-7RLL
Performance specifications
Access time (average) 12 14.5 14.5
(track to track) 3 4 4
Maximum stroke 25 23.5 23.5
Rotation speed (rpm) 4,000 3,800 3,800
Data transfer rate (Mbps) 18.9 to 31.6 24.9 to 36.0 24.9 to 36.0
Power requirements
DC voltages (V) +5 only +5 only +5 only
Power (typical)
Seek (W) 3.6 2.0 2.8
Read (W) 2.8 2.8 2.8
Write (W) 2.8 2.8 2.8
Standby mode
(Spin only) (W) 0.4 0.4 0.4
Sleep mode
(Motor off) (W) 0.15 0.4 0.4
Spin-up mode (mA) 780 940 940
Items

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1.5 Keyboard
The 82-(USA) or 84-(European) keyboard is mounted on the T4850CT’s system unit, and is
connected to the keyboard controller on the system board through a 19-pin flat cable. The
keyboard is shown in Figure 1-6.
See Appendix F for optional keyboard configurations.
Figure 1-6 Keyboard

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1.6 TFT Color LCD
The TFT Color Liquid Crystal Display (LCD) contains an LCD module, a Fluorescent Lamp
(FL), and an FL inverter board.
1.6.1 TFT Color LCD Module
The T4850CT TFT color LCD supports 640 x 480 pixels with an internal display controller
and 4096 colors for graphics and characters. This controller includes the functions of Video
Graphics Array (VGA) and Super VGA (SVGA) for external display.
The LCD receives 12-bit data signals, data enable, LP signal, FP signal, and shift clock for
data transmission. All signals are CMOS-level compatible.
The TFT LCD and FL inverter board are shown in Figure 1-7, and specifications for the LCD
are listed in Table 1-3.
Figure 1-7 TFT color LCD
Table 1-3 TFT color LCD specifications
Item Specifications
Number of dots (dots) 640 x 480
Dot pitch (mm) 0.33 (W) x 0.33 (H)
Display area (mm) 211.2 (W) x 158.4 (H)
Contrast 60:1 (minimum)
FL current (mA) 3.7
FL frequency (KHz) 47

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1.6.2 TFT Color Fluorescent Lamp (FL) Inverter Board
The FL inverter board supplies high frequency current to light the LCD’s Fluorescent Lamp.
Specifications for the T4850CT’s FL inverter are listed in Table 1-4.
Table 1-4 FL inverter board specifications
Item Specifications
Input Voltage (VDC) 18
Power (W) 3
Output Voltage (VAC) 1,100
Current (mA) 4.0
Frequency (KHz) 47
Current limits (mA) 2.5 to 4.5

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1.7 Power Supply
The power supply supplies five kinds of voltages to the T4850CT system board. The power
supply has one microprocessor and operates at 500 KHz (power off) or 20 MHz (power on).
It performs the following functions:
1. Determines if the AC adapter or battery is connected to the computer.
2. Detects DC output and circuit malfunctions.
3. Controls the speaker and the brightness of the display.
4. Controls the Battery capacity icon, Power on icon and AC adapter icon on the
status indicator panel.
5. Turns the battery charging system on and off and detects a fully charged battery.
6. Determines if the power can be turned on and off.
7. Provides more accurate detection of a low battery.
8. Calculates the remaining battery capacity.
The power supply output rating is specified in Table 1-5.
Table 1-5 Power supply board output rating
DC Regulation Maximum
Use for Name voltage tolerance current Ripple
(V) (%) (mA) (mV)
System logic, FDD, HDD VCC +5 ±5 2,700 100
RS-232-C, Flash ROM 12V +12 ±5 120 240
Display DSPV +9.5 to +23 –4.02 W –
RAM, CPU B3V +3.3 ±5 1,200 60
RS-232-C M12V –7 to –12.6 – 10 –

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1.8 Batteries
The T4850CT has three types of batteries:
❑Main battery pack
❑Backup battery
❑Real Time Clock (RTC) battery
Battery specifications are listed in Table 1-6.
Table 1-6 Battery specifications
Battery name Material Output voltage Capacity
Main battery Nickel Metal Hydride 12 V 2,600 mAh
Backup battery Nickel Metal Hydride 1.2 V 1,100 mAh
RTC battery Lithium-Vanadium 3.0 V 50 mAh
1.8.1 Main Battery
The removable main battery pack is the computer’s main power source when the AC adapter
is not attached. The backup and main battery maintain the state of the computer when you
enable AutoResume.
1.8.2 Battery Charging Control
Battery charging is controlled by a microprocessor that is mounted on the power supply. The
microprocessor controls whether the charge is on or off and detects a full charge when the AC
adapter and main battery are attached to the computer. The system charges the battery using
quick charge or trickle charge.
NOTE: When the temperature difference between the computer and the battery pack
is more than 10° C, a full charge may be detected even if the battery is not fully
charged. Remove the battery pack for about five minutes to let the computer and
battery reach the same temperature. Then, reinstall the battery pack.

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❑Quick Battery Charge
When the AC adapter is attached, there are two types of quick charges: Quick Charge
1 when the system is powered off, and Quick Charge 2 when the system is powered
on.
Table 1-7 Time required for quick charges
Charge Kind of battery Charging time
Quick Charge 1 Nickel Metal Hydride About 1 hour, 30 minutes
(power off)
Quick Charge 2 Nickel Metal Hydride 2 to 4 hours (typical: 3 hours)
(power on)
NOTES 1: Using Quick Charge 1, the system CPU automatically stops the
charge after two hours and twenty minutes regardless of the condi-
tion of the battery.
2: The time required for Quick Charge 2 is affected by the amount of
power the system is consuming. Use of the fluorescent lamp and
frequent disk access diverts power and lengthens the charge time.
If one of the following occurs, the battery quick-charge process stops.
1. The battery becomes fully charged.
2. The AC adapter or battery is removed.
3. The battery or output voltage is abnormal.
❑Trickle Battery Charge
When the main battery is fully charged and the AC adapter is attached, the micropro-
cessor automatically changes Quick Charge 1 or 2 to Trickle charge.
❑Detection of a full charge
A full charge is detected only when the battery is charging at quick charge, and under
any of the following conditions:
1. A battery voltage fall is detected.
2. The charging time exceeds the fixed limit.
3. The thermal rise (+DT) exceeds the fixed limit.
4. The battery’s temperature is over 60° C.

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1.8.3 Backup Battery
The backup battery maintains data for AutoResume. The power source used to back up the
AutoResume data is determined according to the following priority:
AC adapter > Main battery > Backup battery
The backup battery is charged by the main battery or AC adapter when the system is powered
on. Table 1-8 lists the charging time and data preservation period of the backup battery.
Table 1-8 Backup battery charging/data preservation time
Item Time
Charging Time Power On 20 H
Power Off 75 H
Data preservation period (full charge) 8.0 H
1.8.4 RTC battery
The RTC battery provides power to keep the current date, time and other setup information in
memory while the computer is turned off. Table 1-9 shows the charging time and data preser-
vation period of the RTC battery.
Table 1-9 RTC battery charging/data preservation time
Item Time
Charging Time Power On 24 H
Power Off 24 H
Data preservation period (full charge) 1 month

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2.1 Troubleshooting
Chapter 2 describes how to determine if a Field Replaceable Unit (FRU) in the T4850CT is
causing the computer to malfunction. The FRUs covered are:
1. Power Supply Board
2. System Board(s)
3. Floppy Disk Drive
4. Hard Disk Drive
5. Keyboard
6. Display
7. Status Indicator Panel
The Diagnostic Disk operations are described in Chapter 3 and detailed replacement proce-
dures are given in Chapter 4.
The following tools are necessary for implementing the troubleshooting procedures.
1. A T4850CT Diagnostics Disk
2. A Phillips head screwdriver (2 mm)
3. A Toshiba MS-DOS system disk
4. A 2DD or 2HD formatted work disk for floppy disk drive testing
5. A cleaning kit for floppy disk drive troubleshooting
6. A printer port LED
7. An RS-232-C wraparound connector
8. A printer wraparound connector
9. A multimeter
10. An external 5.25-inch floppy disk drive
11. An external CRT

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2.2 Troubleshooting Flowchart
Use the flowchart in Figure 2-1 as a guide for determining which troubleshooting procedures
to execute. Before going through the flowchart steps, verify the following:
❑Ask the user if a password is registered, and if it is, ask him or her to enter the pass-
word. If the user has forgotten the password, contact your Toshiba representative.
❑Verify with the customer that Toshiba MS-DOS is installed on the hard disk. Non-
Toshiba operating systems can cause the computer to malfunction.
❑Make sure all optional equipment is disconnected from the computer.
❑Make sure the floppy disk drive is empty.
UPDATE

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Figure 2-1 Troubleshooting flowchart (1/2)