Information processing apparatus

An information processing apparatus comprises a main body of the information processing apparatus and a display device which is replaceably connected to the main body. The main body comprises a CPU, a system bus connected to the CPU and a main body connector connected to the system bus. The display device comprises a panel connector connected to the main body connector, a display, and a controller connected to the panel connector for controlling the display in accordance with information received from the CPU.

BACKGROUND OF THE INVENTION 
The present invention relates to an information processing apparatus such 
as personal computer or workstation having a display device. 
A flat panel has been widely used in a display device of an information 
processing apparatus such as portable notebook type or lap-top type 
personal computer or workstation. 
A panel type display device such as a super-twisted nematic (STN) liquid 
crystal panel, a plasma panel, thin film transistor (TFT) panel or an 
electro-luminescence device is frequently used for such a flat panel. 
FIG. 5 shows a construction of a prior art portable information processing 
apparatus. 
In FIG. 5, numeral 1 denotes a flat panel and numeral 2 denotes a main 
body. The flat panel 1 and the main body 2 are electrically interconnected 
by a cable 3. 
A liquid crystal driver for liquid crystal to be used is mounted on the 
flat panel 1 and the cable 3 is connected to the liquid crystal drive in 
the flat panel 1. 
FIG. 6 shows an internal configuration of the flat panel 1 and the main 
body 2. 
In FIG. 6, an STN liquid crystal panel 4 is used for the flat panel 1. As 
to the internal configuration of the main body 2, only those which relate 
to the control of the flat panel 1 are shown. 
In the main body 2, a display memory 13 stores image information (text 
codes and attribute codes). A display controller 11 controls the 
read/write of the display memory 13, and converts the read image 
information to display data which is supplied to a panel controller 12. 
The panel controller 12 makes timing conversion and tonality conversion to 
the input display data in accordance with a specification of the flat 
panel 1 to produce display data 9 and a panel control signal 8. A power 
supply unit 14 supplies a power to the flat panel 1 through a power supply 
line 10. 
The display controller 11 of the main body 2 is connected to a system bus 
16 for connecting an expansion slot 15 for expanding a function of the 
main body 2. The system bus transmits and receives an address signal which 
represents a memory space and an I/O space, a data signal for transmitting 
and receiving data and a command signal for transmitting and receiving 
data. 
On the other hand, the flat panel 1 receives the panel control signal 8, 
the display data 9 and the panel power supply line 10 through the cable 3. 
The panel power supply line 10 is supplied to a liquid crystal drive 
voltage generator 6. 
The liquid crystal device voltage generator 6 generates a liquid crystal 
drive voltage 7 for driving the liquid crystal of the STN panel 4. Numeral 
5 denotes a liquid crystal driver which selects the liquid crystal drive 
voltage 7 generated by the liquid crystal voltage generator 6 in 
accordance with the panel control signal 8 and the display data 9 and 
supplies it to the STN panel 4. 
In this manner, the STN liquid crystal panel 4 can display an image 
corresponding to the input display data 9. 
Other prior art techniques relating to the flat panel are disclosed in 
JP-A-2-308316 and JP-A-373011. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an information 
processing apparatus which permits exchangeable connection of a suitable 
display device to a main body of the information processing apparatus. 
It is another object of the present invention to provide an inexpensive 
information processing apparatus. 
It is other object of the present invention to provide a compact 
information processing apparatus. 
A panel type display device which may be used for a flat panel includes STN 
liquid crystal, plasma and TFT liquid crystal panel electroluminescence 
devices. 
As the demands for the number of tonalities and the trend of multicolor 
increased, the quality and function of the panel type display device and 
the panel controller have been improved. There is also a desire to provide 
a touch panel or light pen to the flat panel. 
Thus, there is a demand that only a display device is replaced so that a 
suitable display device is connected to the main body depending on an 
application. 
In the prior art, it is not possible to meet such a demand because an 
interface between the flat panel 1 and the main body 2 differs depending 
on the type of panel type display device and the presence or absence of 
the touch panel. For example, since the panel control signal 8 and the 
display data 9 differs from type to type of the panel type display device, 
it is necessary to replace the panel controller 12 and the display 
controller 11 in the main body 2 when a different type of panel type 
display device is to be used. 
The present invention provides an information processing apparatus which 
permit the connection of a suitable display device to the main body. 
In order to achieve the above objects, the present invention provides an 
information processing apparatus comprising a main unit including a 
central processing unit (CPU), a system bus connected to the CPU and a 
main unit connector connected to the system bus, and a display device 
including a panel connector pluggable to the main body connector and 
connected to the main body connector, a display and display control means 
for controlling the display in accordance with data received from the CPU 
through the system bus, the main body connector and the panel connector. 
In accordance with the information processing apparatus of the present 
invention, the display device is provided with all circuits required for 
the types of display devices and the interface between the display device 
and the main body is set on the system bus. Accordingly, whatever the type 
of the display device is, any display device suitable for the application 
may be connected to the main body. 
In accordance with the present invention, the information processing 
apparatus which permits the exchangeable connection of a suitable display 
device to the main body of the information processing apparatus is 
provided. The display device may be selectable depending on the purpose 
and the display device may be shared with other information processing 
apparatus. As a result, an inexpensive information processing apparatus is 
provided. Further, since the display device is separated from the main 
body of the information processing apparatus, the main body of the 
information processing apparatus may be compacted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the information processing apparatus of the present 
invention is now explained. 
FIG. 1 shows a construction of the present embodiment of the information 
processing apparatus. 
As shown, the information processing apparatus of the present embodiment 
comprises a flat panel 1 and a main body 2. Numeral 22 denotes a CRT 
connector, numeral 17 denotes a panel connector and numeral 18 denotes a 
main body connector. The main body 2 and the flat panel 1 are pluggably 
connected by male/famale panel connector 17 and a main body connector 18. 
The CRT connector 22 is for outputting a video signal for a CRT and it is 
arranged not in the main body 2 but on a side of the flat panel 1 while 
taking into consideration that an expansion component may be attached to a 
rear side of the main body 2 and a space to arrange the connector in the 
main body 2 is limited. 
An internal configuration of the main body 2 and the flat panel 1 when a 
liquid crystal panel is used is shown in FIG. 2. Only those of the 
internal configuration of the main body 2 which relate to the control of 
the flat panel 1 are shown. 
Numeral 2 denotes the main body which include a power supply unit 14, a 
system bus 16, an expansion slot 15 and a central processing unit (CPU) 
26. Numeral 1 denotes the flat panel which includes a display memory 13, a 
display controller 11, a panel controller 12, a liquid crystal drive 
voltage generator 6, a liquid crystal driver 5, an STN liquid crystal 
panel 4, a display ROM 19, a DAC 20 and a CRT connector 22. 
In FIG. 2, those elements designated by the same numerals as that of the 
prior art information processing apparatus (FIG. 6) have the same function 
as those of the corresponding means of the prior art information 
processing apparatus. 
The information processing apparatus shown in FIG. 2 differs from the prior 
art information processing apparatus (FIG. 6) in that the display 
controller 11, the panel controller 12 and the display memory 13 are built 
not in the main body 2 but in the flat panel 1, the display ROM 19 which 
stores a display BIOS which is a program necessary for the display 
controller 11 and the main body 2 to control the display of the flat panel 
is provided, and the DAC 20 which generates video analog data 21 and the 
CRT connector 22 are provided in the flat panel 1 to permit the connection 
of the CRT to the flat panel 1. As shown, an interface signal of the 
system bus 16 and a panel power supply line 10 are connected to the 
connector. The system bus 16 is used by the CPU of the main body 2 to 
transmit and receive an address signal representing a memory space and an 
I/O space, a data signal for transmitting and receiving data, and a 
command signal for controlling the transmission and the reception of data. 
An operation thereof is explained below. 
In the flat panel 1, when the display controller 11 receives image 
information from the main body 2 through the panel connector 17, it 
modifies the content of the display memory 13 in accordance with the input 
image information. The display controller 11 reads out the image 
information from the display memory 13, converts it to display data and 
outputs it to the panel controller 12 and the DAC 20. 
The panel controller 12 makes timing conversion and tonality conversion to 
the input display data in accordance with the specification of the STN 
panel 4 to produce the display data, and supplies it and the panel control 
signal to the liquid crystal driver 5. The converted display data is pixel 
data of the STN panel 4 which is outputted on real time basis for the scan 
of the STN panel. 
On the other hand, the DAC 20 converts the input display data to an analog 
video signal suitable to the CRT and supplies it to the CRT connector. 
The liquid crystal driver 5 selects a liquid crystal drive voltage 7 
generated by the liquid crystal drive voltage generator 6 in accordance 
with the panel control signal and the display data received from the panel 
controller 12, and supplies it to the STN panel 4. 
The liquid crystal drive voltage generator 6 generates the liquid crystal 
drive voltage 7 for driving the liquid crystal of the STN panel 4, from 
the power supply received from the power supply unit 14 of the main body 2 
through the panel connector 17. 
An example of the interface signals in the panel connector 17 and the main 
body connector 18 is shown in FIG. 9. 
In FIG. 9, A0-A9 denote address signals. D0-D7 denote data signal, AEN 
denotes an address enable signal, and MEMR, MEMW, IOR and IOW denote 
read/write commands for the memory and the I/O devices. IRQ denotes an 
interruption request signal and CLK denotes a reference clock of the bus. 
The image signal from the main body 2 is sent to the display controller 11 
by using those signals. 
Those signals are on the system bus and included in the expansion slot 15. 
The signals of the expansion slot 15 further include a DMA control signal 
but it is omitted since it has no connection with the control of the flat 
panel 1. When the flat panel 1 which need to have a high arithmatic 
operation ability and process a large volume of display data is used, a 
DMA control signal may be added if high speed memory transfer is to be 
done by using the DMA control. 
In FIG. 9, the signals of the panel power supply line 10 are designated by 
5 V, VLCD and GND. 5 V denotes a drive voltage of the circuit in the flat 
panel 1, and VLCD denotes a drive voltage for the liquid crystal. 
A difference between the signals of FIG. 9 and the panel control signal 8 
and the display data 9 of FIG. 6 which are the interface of the prior art 
flat panel 1 is that the timing and the specification of the signals of 
FIG. 9 do not vary with the type of the flat panel 1. 
In addition, in the prior art information processing apparatus (FIG. 6) 
described above, since the interfaces of the data of the main body 2 and 
the flat panel 1 interconnected by the cable are the display data 9 which 
is pixel data produced on real time basis for the scan of the STN panel 
and the panel control signal 8 synchronized therewith, the data 
transmission rate between the main body 2 and the flat panel 1 is high 
when the flat panel such as a color TFT liquid crystal panel or other high 
density display panel and problems arise with respect to the 
synchronization and the noise reduction. 
On the other hand, in the information processing apparatus of the present 
embodiment, since the data interface of the main body 2 and the flat panel 
1 is the image information transferred over the system bus at a fixed data 
rate without regard to the type of the flat panel 1, the synchronization 
and the noise reduction are not difficult to attain even if the flat panel 
such as the color TFT liquid crystal panel or other high density display 
panel is used. 
Contrary to the above advantage, there is the following disadvantage. In 
the interface of the prior art flat panel 1, the signal lines are as many 
as twenty including the panel control signal 8 and the display data 9. 
However, in the example shown in FIG. 9. 50 signal lines are required. 
There is a trend of increase of the signal lines as the multi-colorization 
and the high density of the flat panel 1 are promoted, but even in that 
case, the signal lines are up to 30 to 40. The increase of the signal 
lines leads to the increase of the volume and cost of the main body 
connector 18 and the panel connector 17. Further, since the flat panel 1 
is pivotable, there is a difficulty in the construction. Accordingly, it 
is essential to reduce the signal lines. In FIG. 9, the address signals 
A0-A19 and the data signal D0-D7 are separate although they may be 
assigned to one signal line which is used by time sharing. The above 
disadvantage may be solved by the time-sharing. 
As shown in FIG. 3, the CRT connector 22 may be provided in the main body 
2. 
In this case, the analog video signal from the DAC 20 to the CRT connector 
22 is added as the interface of the panel connector 17 and the main body 
connector 18. An apparatus which uses a flat panel with a touch panel is 
now explained. 
An internal configuration of the main body 2 and the flat panel 1 is shown 
in FIG. 4. As to the internal configuration of the main body 2, only those 
which relate to the control of the flat panel 1 are shown. 
In the illustrated configuration, the flat panel 1 of the information 
processing apparatus shown in FIG. 2 has been replaced by the flat panel 
with a touch panel. 
The configuration of the flat panel shown in FIG. 4 differs from that of 
the flat panel shown in FIG. 2 in that the former is provided with a touch 
panel 30 and a touch panel controller 31. 
The touch panel 30 is overlayed on the display screen of the STN panel 4, 
and the touch by a user is detected for each section. The touch panel 
controller 31 transfers the detection output of the touch panel 30 to the 
main body 2 through the panel connector 17. 
The touch panel controller 31 is connected to the system bus 16 through the 
panel connector 17 and the main body connector 18 as is the display 
controller 11. 
Accordingly, the CPU of the main body 2 which is connected to the system 
bus 16 may utilize the detection output of the touch panel for any 
purpose. 
Like the embodiment of FIG. 4, the present invention may be applied to an 
ATM terminal. In the ATM, the user interface is important and the display 
device and the entry device are of special design unlike those of consumer 
products such as a personal computer. In this case, the special device may 
be connected in place of the flat panel 1 and the main body 2 may be 
shared with the personal computer in order to enhance a development 
efficiency. 
In accordance with the information processing apparatus of the present 
invention, the signals on the system bus 16 are used as the common 
interface to the flat panels of various types and the main body and the 
hardware which depends on the type of flat panel is provided in the flat 
panel. Accordingly the flat panel may be replaced without modifying the 
hardware of the main body. Since the signals on the system bus 16 are used 
as the common interface to the flat panels of various types and the main 
body, various types of input/output devices such as a touch panel and a 
light pen may be connected to the main body. 
Further, where the display ROM which stores the software to control the 
display is built in the flat panel 1, the modification of the software, in 
addition to the hardware, of the main body is eliminated. 
In the prior art portable information processing apparatus, a packaging 
space in the main body is short because of the enhancement of functions 
and the compactness, and the size reduction of a circuit board of the main 
body has been demanded. On the other hand, there is still a room for 
reduction of a packaging space in the flat panel because a minimum size of 
the liquid crystal panel is secured and high density integration of the 
liquid crystal driver has been attained. 
Accordingly, by building the display controller 11, the panel controller 12 
and the display memory 13 in the flat panel 1 as they are in the present 
embodiment, the number of parts of the main body is reduced and the 
compactness of the information processing apparatus is attained. 
Embodiments of the present invention are shown in FIGS. 7 and 8. 
FIG. 7 shows an application to an overhead projector (OHP) 32. The OHP 32 
normally displays an image printed or hand-written on a transparent sheet 
onto a screen. Recently, an OHP liquid crystal panel 33 which is used in 
place of the OHP sheet so that an image displayed on the liquid crystal 
panel is displayed on the screen has been marketed. Since the OHP liquid 
crystal panel does not need printing and permits correction with ease and 
can display animation unlike the OHP sheet, it has become popular as a 
presentation tool. 
In the present embodiment, the OHP liquid crystal panel 33 is connected in 
place of the flat panel 1 of FIG. 3. The main body 2 and the liquid 
crystal panel 33 are interconnected by the cable 34 through the main body 
connector 18. FIG. 8 shows a construction of the OHP liquid crystal panel 
33. The OHP liquid crystal panel 33 comprises two interlinked cases, a 
front unit 35 and a rear unit 36. The front unit 35 includes an STN panel 
4 and a peripheral circuit such as a display controller 11, as does the 
flat panel 1 of FIG. 2. The rear unit 36 includes a back-light unit, a 
light conducting plate 37, a cathode tube 38 and an inverter 39 for 
driving the cathode tube. When the OHP liquid crystal panel 33 is to be 
used as a conventional personal computer, the front unit 35 and the rear 
unit 36 are overlapped and it is directly connected to the main body 
connector 18 as shown in FIG. 1. When it is to be used for the OHP 32, the 
OHP liquid crystal panel 33 is removed from the main body 2 and the rear 
unit 36 is removed from the OHP liquid crystal panel 33. The front unit 35 
is connected to the main body 2 through the cable 34 and laid on the OHP 
32. 
A reason why the OHP liquid crystal display 33 is divided into the front 
unit 35 and the rear unit 36 which is removable from the front unit 35 is 
explained below. Since the OHP 32 projects a light from the bottom plane 
of the OHP liquid crystal panel 33 to display the image on the liquid 
crystal onto the screen, it is necessary to prevent the light emitted from 
the OHP 32 from being intercepted by the light conducting plate 37 and the 
case. The light from the cathode tube 38 may be used for the screen 
display, but the construction of FIG. 8 is preferable because there is a 
big difference between the brightness when viewed directly by an eye and 
the brightness when projected on the screen. 
In the present embodiment, since the liquid crystal panel may be shared for 
the normal use and the OHP use, the cost is reduced and the OHP system is 
compacted. It is effective to make presentation by carrying the apparatus. 
While the present invention has been shown and described in connection with 
the flat panel display, the present invention is applicable to any display 
device which uses the interface of the flat panel.