JPH05188891A - System and method for display control - Google Patents

Abstract

PURPOSE:To reproduce a picture state when a power source is turned off by switching a device to a standard display device even when an option display device used last time is detached in the case of starting the system in a redume mode in a computer system which can not simultaneously display at the standard display device and the option display device. CONSTITUTION:A first inspection value common for respective R, G and B is written in all the DAC data registers 55 and by comparing the level of R, G and B display signals outputted from a RAMDAC 53 with a reference value, it is judged whether a color CRT is connected or not. Further, a value same as the first inspecting value is written to the G, and a value lower than the first inspecting value is written to the R and B. Then, by comparing the level of the R, G and B display signals with the reference value, it is judged whether a monochromatic CRT is connected or not. According to these judged results, the drive of a standard display device 37 or the option display device is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an LCD (liquid crystal display).
The present invention relates to a display control system and method applied to a computer system that is equipped with a flat panel display such as a d crystal display) or a plasma display as a standard equipment, and can optionally connect a CRT display.

[0002]

2. Description of the Related Art Conventionally, a portable personal computer such as a laptop type is equipped with a flat panel display such as an LCD display or a plasma display as a standard display device. These flat panel displays typically display data using gray scale. A color LCD has also been developed, but the number of colors that can be displayed is small. Therefore, a color CRT (may be a monochrome CRT) is optionally connectable.

Among such computers, there is a computer in which it is impossible to simultaneously display the standard display device and the display device optionally connected. In such a computer, whether or not an optional display device is connected is automatically determined when the power is turned on. That is, when the power is turned on, the basic input /
The initialization and reliability test routines in the output system (BIOS) are executed to determine whether the optional display device is connected, and if so, display the data on the optional display device. If the optional display device is not connected, the data is displayed on the standard display device.

Whether or not the above-described optional display device is connected is determined by, for example, VGA (Video).
In the case of a display control system such as a Graphic Array adapter, specific data for determining whether or not the CRT display is connected is written in the video RAM (VRAM), and the specific data read from this VRAM is D / A.
It is converted into an analog value by the converter and output. R due to the load of the CRT connected to the R, G, B output terminals of the DAC
The GB signal changes, and CR depends on the level of this RGB signal.
It is determined whether T is connected.

[0005]

However, in the above-mentioned conventional method, the resume mode (N
MI (Non-Maskable Interrup
t) Before power is cut off, if the mode) in which system data indicating the operating condition of the CPU is saved in response to the power-off signal and the saved data is restored in response to the NMI power-on signal) is set. When the operating conditions of the system (CPU registers, processing data, status data, etc.) that were set to are saved in the backup memory and power is supplied again, the saved contents are restored in the backup memory and the power is saved. When interrupted, it is configured to continue the interrupted process. Therefore, when the power is turned off and then on again in the resume mode, the initialization and reliability test routines are not executed, and it is not possible to judge whether the optional display device is connected. Not done. Therefore, when the resume mode is set and the optional display device is selected by the setup process, the power is turned off, the user disconnects the optional display device from the computer main body, and then the power is turned on again. When set to, the resume function is activated to try to display data on the optional display device. Therefore, in practice, there is a problem that the data is not displayed on the optional display device or the standard display device.

Further, as described above, in the related art, since the specific data is written in the VRAM to determine whether the CRT is connected, the original data is destroyed. Therefore, there is a problem that the original display contents cannot be reproduced even though the resume mode is set.

According to the present invention, in a computer system in which a standard display device and an optional display device cannot be displayed at the same time, when the system is set up in resume mode, the previously used option display device is removed. It is an object of the present invention to provide a display control system and method capable of reproducing the screen state when the power was last turned off by switching to the standard display device even in the case of the above.

[0008]

A display control system according to the present invention is an NMI (Non-Maskable In).
The system data indicating the operating condition of the CPU is saved in response to the power-off signal, and the NMI (No
n-Maskable Interrupt) A display control system for a computer system having a resume function for restoring saved data in response to a power-on signal, a flat panel display as a standard display device, and a CRT display device optionally connectable. In the above, the setting means for setting whether to use the standard display device or the optional display device as a display device, and to determine whether or not the optional display device is connected when the computer system is started in the resume mode. And a means for driving the standard display device for display regardless of the setting of the setting device when the determining device determines that the option display device is not connected.

Further, the display control system according to the present invention has a flat panel display as a standard display device and optionally has a CRT (Cathode Ray).
In a display control system of a computer system to which a display device can be connected, a video memory for storing display data, writing and reading of the display data to and from the video memory, and display on the standard display device or the optional display device are performed. R (Red), G (Green), B (output to the CRT from the digital display data output from the graphic subsystem, which has a graphic subsystem for outputting digital display data to be output and a plurality of color registers. Blue)
Digital / analog (D /
A) First judging means for writing the first inspection data in the converter and the plurality of color registers, and judging whether or not the color CRT is connected from the levels of the R, G, B display signals output from the D / A converter. And a second determining means for determining whether or not the monochrome CRT is connected based on the levels of the R, G, B display signals output from the D / A converter as a result of writing the second inspection data in the plurality of color registers. And is provided.

Further, the display control method according to the present invention has a flat panel display as a standard display device, and a CRT display device can be optionally connected.
A video graphics array (Video Graphic Array) and a plurality of color registers, and digital display data output from the graphics subsystem is output to an R (R).
In a portable computer system having a digital / analog (D / A) converter that outputs display signal levels of ed), G (Green), and B (Blue), a display control method for determining connection of an optional display device, The first inspection data is written in the plurality of color registers, and as a result, the color CRT is selected from the levels of the R, G, B display signals output from the D / A converter.
Is connected, the second inspection data is written to the plurality of color registers, and as a result, the D / A
It is characterized in that whether or not the monochrome CRT is connected is determined from the levels of the R, G, B display signals output from the converter.

[0011]

The means for judging whether or not the optional display device is connected judges whether or not the CRT display device is optionally connected when the system is started up in the state where the resume mode is set. Here, when it is determined that the option display device is not connected, the display driving means, regardless of the setting of the setting means for setting which of the standard device or the option display device is used as the display device, The standard display device is driven for display.

The graphics subsystem writes and reads display data to and from the video memory and outputs digital display data to be displayed on the standard display device or the optional display device. The digital / analog (D / A) converter has a plurality of color registers, and converts the digital display data into R (Re
The display signal levels of d), G (Green), and B (Blue) are output. The first judging means writes the first inspection data in the plurality of color registers, and judges whether or not the color CRT is connected from the levels of the R, G and B display signals which are changed by the previous D / A converter. The second determination means writes the second inspection data in the plurality of color registers, and determines whether or not the monochrome CRT is connected from the levels of the R, G, B display signals.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall block diagram showing an example of a computer system to which the display control system and method of the present invention are applied.

In FIG. 1, 10 is a system bus, and 11 to 28 are components connected to the system bus 10, respectively. Of these components, 11
Is a CPU (main CPU) that controls the entire system. Here, when the power is turned on, the BIOS-RO
The M12 is accessed to execute a CRT connection presence / absence determination processing routine as shown in FIG.

12 is a BIO in which a fixed program is stored.
This is an S-ROM, and here, a CRT connection presence / absence determination processing routine shown in FIG. 6 and a setup processing routine for selecting whether to use the standard device (FPD) or the optional display device (CRT) are entered. Stores output related control programs. Reference numeral 13 denotes an R which constitutes a main memory in which programs and data to be processed are stored.
AM is a DMA controller (DMAC; Direct M) that performs direct memory access control.
It is an emory access controller). Reference numeral 15 is an interrupt controller (PIC; Programmable Int) that can be set by a program.
16 is an interval timer (PIT; P) that can be set by a program.
Programmable Interval Time
r).

Reference numeral 17 denotes a timepiece module (RTC; Real-time Clock) having its own operating battery, which stores date, time information and the like. Reference numeral 18 denotes a large-capacity additional RAM that can be inserted into and removed from a dedicated card slot of the main body. Here, any one of four types of memory including an existing memory card of 1 MB and 2 MB and a new memory card of 4 MB and 8 MB is added. The card can be mounted.

Reference numeral 19 is a backup RAM serving as a data storage area for realizing the resume function, to which a backup power supply (VBK) is supplied. Backup RAM
19 stores the contents of the memory and registers when the power is turned off in the resume mode.

Reference numeral 20 denotes a floppy disk controller (FDC). In this embodiment, two floppy disk drives 32A and 32B are controlled, but one floppy disk drive (for example, FDD) is used.
32B), a 2.5-inch hard disk can be mounted, and the system can be easily upgraded.

Reference numeral 21 is a printer controller (PRT-C).
ONT), for example, a 5-inch external floppy disk drive 33, a printer 34, or the like is selectively connected via a connector.

Reference numeral 22 denotes an input / output interface (UAR
T; Universal Asynchronous
Receiver / Transmitter),
RS-232C interface device 35 as required
Etc. are connected. 23 is a keyboard controller (KB
C), which controls the input of the keyboard 36 provided integrally with the main body of the apparatus on which the CPU board is mounted.

Reference numeral 24 is a display controller (DISP-CO
NT) and only the liquid crystal display device (LCD) is displayed here, but it is possible to control the display drive of the CRT display device 49 as an optional display. 27 is a video RAM (VRAM) to which a backup power supply (VBK) is supplied.

Reference numeral 28 denotes a power supply circuit (intelligent power supply) 30, which will be described later, via the system bus 10.
A parallel / serial interface (PS-IF) for connecting to the PU 11, and here, the power supply circuit 3
0 power control CPU (PC-CPU) 306
It has a serial-to-parallel conversion function to transfer data to and from the serial interface. Two
Reference numeral 9 denotes a power supply adapter (hereinafter referred to as an AC adapter) that rectifies and smoothes a commercial AC power supply (AC) to obtain a DC power supply of a predetermined potential, which is plug-in connected to the main body of the portable computer.

30 is a power control CPU (PC-
A power supply circuit (intelligent power supply) equipped with a CPU, 33 is a power switch for turning on / off the power supply of the portable computer main body, and 31L and 31R are respectively configured by rechargeable batteries, and are attached to and detached from the apparatus main body (PC main body) Possible main battery in pack format (MB
ATA, B-BATB), and when one of the batteries is selected as a usage target (power supply target) under the control of the power supply circuit 30 at the time of driving, and the battery is discharged up to the usage limit. The battery to be used is switched, and the other battery is used.
31S is a sub-battery (S-BAT) built in the main body, which is also composed of a rechargeable battery, and is a RAM 1
3, the backup power supply (VBK) is supplied to the memories such as the expansion RAM 18 and the video RAM 27 that need to be backed up.

Reference numeral 40 denotes an expansion bus connector (EBC) for expanding functions, which is, for example, an external hard disk (external H).
DD), etc. are selectively connected as necessary, or various components (eg, keyboard, C) for function expansion.
It is selectively mounted in an expansion unit equipped with an RT display, a large-capacity memory, a personal computer mounting mechanism, etc.) and connected to a circuit.

Reference numeral 41 is an HDD mounting type (HDD, FDD
When mounting the system to 1 each), the built-in HDD
It is a built-in HDD interface (HDD-IF) for interface connection (with HDC), and when the system is upgraded, the built-in HDD interface is connected via the connector 42 instead of the floppy disk drive (FDD) 32B.

Reference numeral 50 designates a status display section comprising a plurality of status display LEDs (L1 to L9) which are display drive controlled under the control of the power control CPU 306 of the power supply circuit 30. FIG. 2 is a flow chart for determining whether or not the option display device is connected and performing the corresponding resume process based on the determination result.

That is, the CPU 11 performs an option display device automatic determination process in step S1. In step S3, the CPU 11 determines whether the option display device is connected. If the option display device is connected, the CPU 11 executes step S7.
At, the activation control of the option display device (CRT) 49 is performed. On the other hand, when it is determined that the option display device is not connected, the CPU 11 controls the activation of the standard display device (LCD) 37 in step S5.

Further, the CPU 11 displays the data saved in the backup memory 19 in step S9 (for example, the color register 5 in the DAC 53 described later).
Restore to 5). Finally, the CPU 11 executes step S
At 11, the program that was running when the system was turned off is re-executed from where it left off.

3 and 4 are detailed block diagrams of the display controller 24 shown in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. 3 and 4, the graphic subsystem 51 is, for example, V
A graphic subsystem called a GA (Video Graphic Array) adapter, which accesses the video RAM (VRAM) 27 to perform gradation display control on the LCD 37 and controls the option display device (C).
The display control of the color CRT or the monochrome CRT is performed for the (RT) 49.

Digital-to-analog converter (RAMD
AC) 53 displays the display data VID (pixel video data) generated from the graphic subsystem 51 to RA.
R, G, B are converted into analog data according to the value of the palette 55 in the MDAC, that is, the internal conversion data register (sometimes called DAC data register or color register).
Output signal or a multi-gradation display signal. DAC
The data register 55 is composed of 256 registers (each register is composed of 8 bits). The RAMDAC 53 is provided with direct data input terminals 53A (SD0 to 7) for setting inspection data (described later) in the internal DAC data register 55, and whether the external display device (CRT monitor) 49 is connected or not. When inspecting, R, G, B from this data input terminal 53A (SD0-7)
Common to all DAC data registers 55, 12
Test data of (h), 12 (h), and 12 (h) are written. This is different from the conventional case.
The contents of AM27 are not changed. Therefore, it is impossible to know what value is set in the VRAM. VGA for example
For graphic subsystems, the text data is
It is composed of character data and attribute data. The attribute data takes 16 values from 0 to F. These 16 values are used as pointers to 16 palette registers (51b in FIG. 3), and one of the palette registers is selected. One of the 256 DAC data registers 55 is selected according to the content (8 bits) of the selected palette register. Therefore, 256
It is not known which of the DAC data registers 55 will be selected. Regardless of which of the 256 DAC data registers 55 is selected, the same value is written in all of the 256 DAC data registers 55 in order to keep the output voltage of the connector to which the CRT is connected always constant. Need to leave. Under such conditions, CRT
It is possible to correctly determine whether or not the CRT is connected by detecting the voltage fluctuation due to the connection of the.

Next, 12 (h), 12 (h), 12 are commonly used for all the R, G, B DAC data registers 55.
A method for determining whether or not a color CRT is connected by writing (h), and DA for all R, G, B
04 (h), 12 (h), 04 in the C data register 55
A method of writing the test data of (h) and determining whether or not the monochrome CRT is connected will be described below.

In FIG. 5, the vertical axis represents the display signal level applied to the load of the CRT connected to the R, G, B terminals of the DAC,
The value set in the DAC data register 55 (0
.About.3F), each characteristic diagram is shown when there is no load, that is, the CRT is not connected, and when there is a load, that is, when the CRT is connected. As can be seen from this figure, the value of 12 (h) is the display signal level (voltage) of R, G, B when there is no load and the display signal level (voltage) of R, G, B when there is a load. A value approximately midway between and is selected as the reference value. The comparator 63 of the monitor detector 57 outputs "0" if the R, G, and B display signal levels are below the reference value, and outputs "1" if it is above the reference value. Comparator 6 of monitor detector 57
3 has a gate circuit that satisfies the following logical expression, and sets the logical calculation result in bit 4 of the status register (MD register).

[0033]

[Equation 1]

As can be seen from the above logical expression, R, G, B
Common to all DAC data registers 12 (h), 1
When 2 (h) and 12 (h) are written and all of R, G, and B are lower than the reference value, it is determined that the color CRT is connected. At this time, it cannot be determined that the monochrome CRT is connected by the values of 12 (h), 12 (h), and 12 (h) used for the CRT connection determination.

Further, when 04 (h), 12 (h) and 04 (h) are written in common to all the R, G and B DAC data registers, and when the voltage level of G becomes lower than the reference value, monochrome Judge that the CRT is connected. The monochrome CRT is configured to receive only the G signal. Therefore, the value of "04 (h)" is written in the DAC registers of R and B so that the R signal voltage level and the B signal voltage level both become lower than the reference value regardless of whether there is a load or not. Only in the DAC register "12
(H) ”is written.

When inspecting whether the connected CRT monitor is a color monitor or a monochrome monitor,
From the data input terminal 53A (SD0 to 7), R,
Common test data 04 (h), 12 (h), 04 (h) are written in all G and B DAC data registers 55. In addition, here, of the R, G, and B display signal output terminals output from the DAC 53, G (Green)
The output terminal n) is used as a display signal output terminal of the monochrome CRT monitor.

The monitor detection unit 57 determines whether or not the external display device (CRT monitor) 49 is connected based on the R, G, B or multi-gradation display signal levels output from the DAC 53, and the option display device is a color CRT. It is determined whether it is a monitor or a monochrome CRT monitor. That is, the monitor detection unit 57 compares the level of the display signal applied to the load of the CRT as a reference value, and the color CRT is connected or the monochrome CRT is connected from the voltage fluctuation (drop) due to the load connection. It is determined whether or not there is a register (M
D register) 59.

The video RAM (VRAM) 27 is VGA5.
VRAM controller (V-RAM / CNT) 5 in 1
The data read by the access of 1a is the palette 51b.
Is output to the DAC 53 via. In this embodiment, the battery backup voltage (VBK) is maintained even when the power is off.
Is applied to save the display data immediately before the power is turned off.

FIG. 6 is a flow chart showing the CRT connection presence / absence judgment processing in the apparatus of the above embodiment. In this embodiment, all the R, G, and
“12 (h)”, “12 (h)”, “12” corresponding to B
(H) "is set, and the display signal levels of R, G, and B output to the CRT connector at that time are compared with the comparator 63 in the monitor detection unit 57 as shown in FIG. When the OR of the comparison results of G and B is logic "1", it is determined that the color CRT monitor is connected, and the logic "1" is set in the MD register (bit 4) 59. Also, the color CRT is connected. If it is determined that all the R, G, and
"04 (h)", "12 (h)", "04" corresponding to B
(H) ”data is set, and similarly, the monitor detection unit 5
By the comparator 63 in 7, the R, G, B at that time
When the OR of the comparison results of R, G, and B is logic "1", the monochrome C
Determine that RT is connected, and set logic "1" to M
It is set in the D register (bit 4) 59. This M
By referring to the contents of the D register 59, it is possible to determine whether or not the CRT monitor 49 is connected and whether the connected monitor is color or monochrome. The operation of the embodiment of the present invention will be described below.

When the power is turned on in the resume mode,
Whether the CRT is connected to the system or not is determined by the system control program in the BIOS stored in the ROM 12 from the time when the power is turned on to the time when the display device is resumed.

That is, in the start-up process when the system power is turned on, the resume mode flag is "1".
When it is (resume on), initialization of the VGA 51,
Processing such as inspection of the video RAM (VRAM) 27 (see FIG. 6,
After performing steps S21 to S25), all R. “12 (h)”, “12 (h)”, and “12 (h)” are set corresponding to G and B (FIG. 6, step S27).

As a result, the CRT connected to the DAC 53
The respective display signal levels of R, G, and B which change depending on the load of No. 5 are compared with the reference value shown in FIG.
Is set to. That is, the monitor detection unit 57 uses the DAC
R output from the DAC data register 55 in 53,
G, B = 12 (h), 12 (h), 12 (h) (00
(H) min to 3F (h) max) each display signal level of the analog amount corresponding to each data is compared with a reference value, and when any one of the three display signal levels is lower than the reference value, MD "1" indicating that the color CRT monitor 49 is connected (with load) is set in bit 4 of the register 59.

In step S29, if bit 4 of the MD register is "1", it is determined that the color CRT is connected, and the CPU 11 controls the activation of the color CRT in step S31. In other words, if the screen display is possible in the previous use state, the saved DAC data is restored to each register in the DAC 53, the system data is restored to the register of each input / output device, and the previous use state is used. Display the screen just before the power was cut off on the display device (standard display device or optional display device) that was in use, and if the CRT monitor that was in the previous use state was removed, The default gradation data is set in the mapping RAM 61, and the screen immediately before power-off at the time of previous use is displayed on the standard display device (steps S33 to S35 in FIG. 6).

In this case, the video RAM (VRAM) 27
Is not rewritten (data contents are not destroyed) in the state inspection of the option display device 49 described above, and thus the VRAM 27 is backed up by the battery so that the previous data is stored in the VRAM 27 as it is. It is possible to start the display in the resume mode.

On the other hand, if bit 4 of the MD register 59 is not "1" in step S29, that is, if the color CRT is not connected (no load), the CPU 11 continues in step S39. D
Each of the data registers 55 of the AC 53 has R, G, B
Corresponding to "04 (h)", "12 (h)", "04
(H) ”is set.

In this case, R output from the DAC 53,
Each of the G and B display signal levels is compared with a reference value by a comparator 63 in the monitor detector 57, and a monochrome CRT is displayed.
Information indicating whether or not a monitor is connected is set in the MD register 59. That is, the monitor detection unit 57
R, G, B = 04 (h), 12 (h), 04 (h) output from the DAC data register 55 in the AC 53
Each display signal level of the analog quantity according to the data of is compared with the reference value, and when the display signal level of G is lower than the reference value,
The bit 4 of the MD register 59 is set to "1" indicating that the monochrome CRT is set.

When it is determined in step S41 that bit 4 of the MD register 59 is "1", that is, the monochrome CRT is connected, the CPU 11 determines in step S41.
In step 43, the monochrome CRT is activated and the process proceeds to step S33. If it is determined in step S41 that the monochrome CRT is not connected,
In step S45, the CPU 11 controls the activation of the standard display device (flat panel display) 37, and proceeds to step S35 described above.

The inspection data set (12
(H), 12 (h), 12 (h) / 04 (h), 12
(H) and 04 (h) are data (12 (h), 12) common to all the R, G, B DAC data registers 55 in the DAC 53 from the direct input terminals 53A (SD0 to 7) of the DAC 53 at the time of inspection. (H), 12 (h) / 04
This is realized by setting (h), 12 (h), 04 (h)). As described above, the contents set in the MD register 59 are output to the VGA 51, and further the VG
It can be read into the CPU 11 via A51.

In addition to the display data VID (pixel video data), the signals transferred between the VGA 51 and the DAC 53 include WPLTN (a signal to be written in the DAC data register and the color palette) and RPLTN (D
AC data register and color palette read signal), PCLK (video pixel clock signal used on DAC 53 to latch display data VID), BLNK (active row display monitor blank pulse signal), SA (DAC data register) Although there is a latch address for selection) and the like, detailed description thereof will be omitted here.

Further, in the above embodiment, the CRT monitor is used as the option display device, but the present invention can be applied to other display devices such as a flat type color display. Furthermore, the detection of whether or not the option display device is connected is not limited to the detection mechanism that does not require special hardware for the above-described detection. For example, as described in Japanese Patent Application No. 1-254961, the hardware is configured so that the signal level changes according to the type of display device connected, and the signal level is detected by the hardware. It is also possible to use a connection detector.

Further, in the above embodiment, the monitor detection unit 57 is used.
Although the status register (MD register) 59 for latching the output from the comparator 63 is provided therein, the comparison result from the comparator 63 may be directly output to the VGA 51.

[0052]

As described above in detail, according to the present invention,
In a computer that cannot display both the standard display device and the optional display device at the same time, when the system is started up in resume mode, the presence / absence of the optional display device is determined to confirm that the optional display device is not connected. When the judgment is made, the standard display device is controlled by the display drive regardless of the setting of the display drive, and even if the previously used option display device is removed when the system is started in the resume mode. ,
By switching to the standard display device, it is possible to reproduce the screen state when the power was last turned off.

[Brief description of drawings]

FIG. 1 is an overall block diagram of a computer system according to an embodiment of a display system of the present invention.

FIG. 2 is a flowchart showing a display device automatic determination processing procedure at the time of starting the resume mode in the embodiment.

FIG. 3 is a block diagram showing details of the display controller shown in FIG.

FIG. 4 is a block diagram showing a configuration of a DAC and a monitor detection unit in the embodiment.

FIG. 5 is a characteristic diagram of display signal levels and inspection values with and without a CRT connection in the embodiment.

FIG. 6 is a flowchart showing details of the automatic display determination processing procedure shown in FIG. 2 in the embodiment.

[Explanation of symbols]

10 ... System bus, 11 ... CPU, 12 ... BIOS-
ROM, 13 ... RAM, 14 ... DMA controller (D
MAC), 15 ... PIC, 16 ... PIT, 17 ... Clock module (RTC), 18 ... Expansion RAM, 19 ... Backup RAM, 20 ... Floppy disk controller (FDC), 21 ... Printer controller (PRT-C)
ONT), 22 ... Input / output interface (UAR
T), 23 ... Keyboard controller) KBC), 24
... Display controller (DISP-CONT),
27 ... Video RAM (VRAM), 28 ... Parallel / serial interface (PS-IF), 29 ... AC adapter, 30 ... Power supply circuit, 31L, 31R ... Main battery, 31S ... Sub battery, 32A, 32B ... Floppy disk drive ( FDD), 33 ... External floppy disk drive, 34 ... Printer, 35 ... RS-2
32C interface, 36 ... Keyboard, 37 ... Standard display device (LCD), 49 ... Optional display device (C
RT), 51 ... Video graphic array (VG
A) Adapter, 53 ... Digital-to-analog converter (D
AC), 55 ... DAC data register, 57 ... Monitor detection unit, 59 ... Gate array, 61 ... Map RAM, 63
…comparator.

Claims (3)

[Claims] 1. NMI (Non-Maskable I)
system data indicating the operating conditions of the CPU in response to the power-off signal, and NMI (N
on-maskable interrupt) In addition to having a resume function of restoring saved data in response to a power-on signal, a flat panel display as a standard display device, and an optional CRT
(Cathode Ray Tube) In a display control system of a computer system to which a display device can be connected, setting means for setting whether to use the standard display device or the optional display device as the display device, and the computer in the resume mode. A means for judging whether or not the option display device is connected when the system is started up; and a standard display device regardless of the setting of the setting means when the judgment means judges that the option display device is not connected. And a means for driving the display of the display control system. 2. A flat panel display as a standard display device, and optionally a CRT (Cathode)
In a display control system of a computer system to which a Ray Tube display device can be connected, a video memory for storing display data, writing and reading of the display data to and from the video memory, and displaying on the standard display device or the optional display device are performed. R (Red), G (Green), B output to the CRT from the digital display data output from the graphic subsystem having a graphic subsystem for outputting digital display data to be displayed, and a plurality of color registers. (Bl
ue) a digital / analog (D / A) converter that outputs a display signal level, and write the first inspection data in the plurality of color registers to output R, G, B display signals output from the D / A converter. First judging means for judging whether or not the color CRT is connected from the level, and second inspection data are written in the plurality of color registers, and as a result, the R, G, B display signals outputted from the D / A converter are outputted. 2. A display control system comprising: a second judging means for judging whether or not a monochrome CRT is connected from the level. 3. A flat panel display is provided as a standard display device, a CRT display device can be optionally connected, and a VGA (Video Graphic Ar) is provided.
ray) having a graphics subsystem,
It has a plurality of color registers, and R (Red), G (Green), and B (Bl) output to the CRT from the digital display data output from the graphic subsystem.
A display control method for determining connection of an optional display device in a portable computer system having a digital / analog (D / A) converter that outputs a display signal level of (ue). , And as a result, it is judged from the levels of the R, G, B display signals output from the D / A converter whether or not a color CRT is connected, and the second inspection data is written in the plurality of color registers. A display control method, wherein it is determined whether or not a monochrome CRT is connected from the levels of R, G, B display signals output from the D / A converter.