JPH1040007A - Position reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain highly precise reading by level-fixing the driving signal of a display device among display control signals, preventing a noise component from mixing into the output signal of a tablet, and creating position information. SOLUTION: A position reading period signal generating circuit 9 counts a horizontal scanning signal, compares the counted value with a value preliminarily set by a CPU 1, and supplies a position reading period signal 108 to a signal fixing circuit 8 and a period informing circuit 10 as a low level output when the counted value is turned into the set value. Then, the signal fixing circuit 8 fixes the level of a display data transfer signal and a horizontal scanning signal in the scanning period of a position reading area so that the level changing point of the horizontal scanning signal and the signal changing point of a liquid crystal alternating signal can not be generated. Thus, a noise in the scanning period of the position reading area can be completely evaded and the highly precise position reading can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a position reading device.

[0002]

2. Description of the Related Art In recent years, a portable information terminal uses a liquid crystal display device as a display device, arranges a tablet using a resistive thin film as an input means on a screen thereof, and presses the tablet with a pen or a finger. The input is done by doing. As a conventional technique for accurately reading the pressed position on the tablet, for example, Japanese Patent Application Laid-Open No. 5-150902 discloses an example using a STN type liquid crystal display device.

In such a position reading device in which a tablet is arranged on the screen of a display device, the tablet is made of a transparent resistive film and has horizontal transparent electrodes provided with horizontal electrodes on two opposing sides in the horizontal coordinate axis direction. The tablet has a configuration in which a resistive film and a vertical transparent resistive film which is also made of a transparent resistive film and is provided with a vertical electrode on each of two opposing sides in the vertical coordinate axis direction are provided with a predetermined minute interval therebetween, and such a tablet. Is arranged on the screen of the display device.

A current is applied to the horizontal transparent resistance film between the two horizontal electrodes, and a current is applied to the vertical transparent resistance film between the two vertical electrodes. The voltage between these electrodes is detected. It is supplied to a separate A / D (analog / digital) converter, converted into digital data, and
(Central processing unit).

If an arbitrary position on the tablet is depressed by a pen or the like, the voltage between the two horizontal electrodes changes according to the position of the pen pressed in the horizontal axis direction on the tablet. The voltage between them changes according to the pen pressing position on the tablet in the vertical axis direction. These voltage changes are detected by the CPU based on digital data from the A / D converter, and the horizontal coordinate point and the vertical coordinate point of the pen pressing position on the tablet are obtained. And C
The PU controls the display controller based on the obtained information on the horizontal and vertical coordinate points, thereby driving the pixel at a position on the screen of the display device opposite to the pen pressing position of the tablet to display the pen pressing position. .

FIG. 15A shows a screen of a display device. A display area 101 of the display device has one line composed of X dots in the horizontal direction and lines Y0, Y1,.
··· It consists of Ymax Y lines. In order to display an image in such a display area, as shown in FIG. 15B, a frame signal 301 and a horizontal scanning signal 105 (hereinafter, referred to as a display driving signal) are supplied to a display device. The level of the frame signal 301 is inverted every frame period required to scan the entire display area 101. Therefore, this makes the liquid crystal display device AC in one frame. Further, the horizontal scanning signal 105 is displayed in the display area 1.
., Ymax of the frame signal 301 in order to drive all the lines Y0 in one frame period between the level inversion of the frame signal 301 and the next level inversion. , Y1,... Y
max are sequentially driven. Then, the driven line Y
i (i = 1, 2,..., max) are simultaneously supplied with display data of all dots of the line Yi.

By the way, in the position reading device having the above-described configuration, an electrostatic coupling is formed between the screen of the display device and the tablet, and the capacitance causes the electrostatic coupling to be performed as shown in FIG.
As shown in (c), noise due to the display drive signal of the display device occurs in the tablet. That is, the frame signal 3
When the level of 01 or the horizontal scanning signal 105 is inverted, noise is generated in the signal from the tablet via the capacitance. This noise is particularly large at the changing point of the frame signal 301. Further, when the size of the display device is increased and the tablet area is increased, the amount of such noise is also increased.

When such noise is generated, the voltage between the electrodes of the tablet is disturbed by the noise and A /
The signal is supplied to the D converter, and the CPU performs erroneous position detection.

Therefore, in the technique described in Japanese Patent Application Laid-Open No. 5-150902, in order to prevent this and enable accurate position detection, the timing other than the timing at which the level of the frame signal 301 or the horizontal scanning signal 105 is inverted. The A / D converter takes in the voltage between the electrodes of the tablet when the level of is stable. More specifically,
Each of the lines Y0, Y1,... Ym shown in FIG.
The horizontal scanning signal 105 of ax has the same pulse width, and is output as Y0, Y1,..., Ymax at the falling edge of each signal. The frame signal 301 is formed by counting this clock or the like. Since the levels of the frame signal 301 and the horizontal scanning signal 105 are stable after the rising edge of the clock, the rising edge of this clock triggers The A / D converter takes in the electrode voltage of the tablet.

In order to read the output of the tablet at a timing when the levels of the frame signal 301 and the horizontal scanning signal 105 are stable, the CPU first applies a voltage to the tablet and waits until the applied voltage is stabilized. To detect whether or not the tablet is pressed, and then re-apply a new voltage to the tablet, wait for the applied voltage to stabilize, detect the rising edge of the clock, and detect the detected rising edge. As a trigger, the output of the tablet is fetched via the A / D converter, and the pressed position of the tablet is detected.

[0011]

In the prior art, in order to eliminate noise from the liquid crystal screen to the tablet, the CPU changes the output voltage of the tablet to A / D at the rising edge of the horizontal scanning signal of the liquid crystal screen. Since the coordinate data obtained by digitizing with the converter is read, even after the applied voltage supplied to the tablet is stabilized, the CPU is used until the rising edge of the horizontal scanning signal of the liquid crystal screen appears.
Must interrupt the reading process of the coordinate data,
U has not been considered for distributing U to other processes and effectively utilizing the processing capacity.

Also, regardless of whether or not the pen is pressing the tablet, the horizontal distance between the horizontal electrodes of the tablet is periodically changed.
Since a current is applied to the horizontal and vertical transparent resistive films of the tablet by applying voltages between the vertical electrodes and pen pressing detection is performed,
No consideration has been given to the processing time and power consumption of the CPU spent on pen press detection.

A first object of the present invention is to provide a coordinate reading apparatus which solves such a problem and makes it possible to effectively utilize the processing capability of a CPU.

A second object of the present invention is to provide a coordinate reading apparatus capable of greatly reducing power consumption.

[0015] A third object of the present invention is to provide a coordinate reading device capable of reading with high accuracy.

[0016]

In order to achieve the first object, the present invention detects the end of a display period on a display screen,
First means for setting the position reading period of the pressed point on the tablet; second means for masking the position reading period and the display control signal of the display device;
Third means for causing the PU to perform reading processing of the coordinate position of the pressed point on the tablet, setting the reading period of the pressed point outside the display period of the display screen, and setting the detection period of the pressed position of the tablet on the display screen Is set outside the scanning period.

Thus, even if the tablet is overlaid on the display screen of the display device and the tablet and the display screen are electrostatically coupled, no display control signal is supplied to the display device during the position reading period. There is no noise due to the level change of the control signal, and therefore,
The coordinates of the pressed point of the pressing means on the tablet can be accurately read. Further, since the CPU only has to perform the reading process of the pressed position only during the position reading period, in other periods, the CPU can perform processing operations other than the position reading process, and effectively utilize the processing capability of the CPU. be able to.

In order to achieve the second object, the present invention provides a first means for detecting a change in current flowing through a resistive film due to a start of pressing of a pressing means on a tablet and an end of pressing, and Second means for notifying the CPU of the pressing start and the pressing end of the pressing means in accordance with the detection result by the means; and By reading the position data of the pressed point by reading the data of the position of the pressed point by the pressing means on the tablet, processing the data to obtain the coordinates of the position of the pressed point Alternatively, at the end of the arithmetic processing, a state in which a current flows through only one of the resistive films is set to a standby state for the next pressing.

Thus, only when the tablet is pressed by the pressing means, the CPU causes the current to flow through both of the two resistive films constituting the tablet, thereby reading the data of the pressed point of the tablet and determining the coordinate position thereof. Performs the required calculation, and when the pressing means is separated from the tablet, the CPU
Is designed to detect the pressing on the next tablet by allowing the current to flow through only one of the resistive films, so that when the pressing means is separated from the tablet, the power supplied to the tablet can be reduced. Thus, current consumption can be reduced.

Further, in order to achieve a third object, the present invention provides a first means for detecting a change in a current flowing through a resistive film due to a start of pressing of a pressing means on a tablet and a stop of pressing of the pressing means; A second means for notifying the CPU of the pressing start and the pressing stop of the pressing means in accordance with the detection result by the means, and the CPU, upon notification of the pressing start of the pressing means by the second means, By applying a current to each of them, the data of the position of the pressed point by the pressing means on the tablet is read and processed to calculate the coordinates of the position of the pressed point. Upon completion of the reading or the arithmetic processing, in response to the notification of the start of the pressing of the pressing means by the second means, a state in which current flows through only one of the resistive films is set to a standby state for the next pressing, and the position data of the pressed point is stored. With interrupting the reading operation of discards the coordinate data of the position of the resulting pressed point immediately before as invalid.

Thus, similarly to the present invention for achieving the second object, the power consumption can be reduced, and the coordinate data having poor reliability obtained immediately before the pressing means is separated from the tablet is discarded. Therefore, the position reading accuracy is greatly improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments described below, a display device has a resolution of 480 dots in the horizontal direction and 320 lines in the vertical direction. A case will be described as an example where a monochrome STN liquid crystal display device having a display data width of 4 dots to be input is used.

FIG. 1 is a block diagram showing a first embodiment of a position reading device according to the present invention, wherein 1 is a CPU, 2 is a tablet, 3 is a switch circuit, 4 is an A / D converter, and 5 is a display device. , 6 is a display memory, and 7 is a display controller. The following is a characteristic part of the present invention, 8 is a signal fixing circuit, 9 is a position reading period signal generation circuit, 10 is a period notification circuit, 108 is a position reading period signal, 109 is a position reading notification signal, and is a broken line. The enclosed portions are the same as those described in the related art.

In FIG. 1, a CPU 1 performs overall control, expands a display screen on a display device 5 into a display memory 6, and reads an analog voltage converted into a digital value by an A / D converter 4. To convert the coordinates into coordinate values on the tablet 2 and control the switch circuit 3 for applying a voltage to the horizontal and vertical electrodes of the tablet 2. The display controller 7 reads and processes the display data from the display memory 6 and supplies the display data to the display device 5 together with a clock synchronized with the display data and the display control signal described in the related art in order to display an image on the display device 5. I do.

The procedure for reading the coordinate data is the same as that described in the prior art. The CPU 1 controls the switch circuit 3 to apply a voltage to the horizontal and vertical electrodes of the tablet 2 and the A / D converter 4 Launch Tablet 2
The electric signal corresponding to the pen pressing position output from the
The data is digitized by the D converter 4, and the CPU 1 reads the digital value, performs an operation, and converts the digital value into a coordinate value.

Here, the signal fixing circuit 8, the position reading period signal generation circuit 9 and the period notification circuit 10 are features of the first embodiment. Hereinafter, these operations will be described with reference to FIGS. It will be described using FIG.

FIG. 2A shows a display area of the liquid crystal display device 5 and a tablet 2 to CP which is a feature of the first embodiment.
U1 indicates the relationship of a position reading area for reading the coordinate position where the pen is pressed, 101 is a display area, and 102 is a position reading area. In FIG. 2A, the display area 10
Reference numeral 1 denotes an area for a display period, and a position reading area 102
Is an area outside the display period. The display area 101 is composed of dots x1, x2,... Xmax in the horizontal direction. Here, the total number of dots x is 480 dots. The vertical direction of the display area 101 is represented by lines Y1, Y2,.
ax, where the total number of lines Y is 321 lines obtained by adding one line to the number of lines that can be displayed on the liquid crystal display device 5. The reason will be described later.

The position reading area 102 is formed by adding N lines outside the display area 101 in the vertical direction.
These lines are denoted by N1... Nmax. The line N1 which is the first line of the position reading area 102 corresponds to the line 322 following the last line 321 of the display area 101. Here, line Y1 to line Nmax (3
21 + N) constitute one frame.

FIG. 2B shows a display control signal corresponding to the display screen of FIG. 2A and various signals which characterize the first embodiment. Reference numeral 103 denotes display data synchronized with the display data. A transfer signal, 104 is display data, 105 is a horizontal scanning signal, 106 is a liquid crystal alternation signal (here, it is assumed that it is inverted every 13 lines and is alternating), 107 is a frame signal, and 108 is this first signal. A position reading period signal 109 which is a feature of the first embodiment, a position reading notification signal 109 which is a feature of the first embodiment, 110 is an actual horizontal scanning signal during the operation of the first embodiment, 111 is This first
9 is an actual voltage waveform of the tablet electrode during the operation of the exemplary embodiment.

In FIGS. 1 and 2, the display controller 7
According to the display data transfer signal 103, data for four dots is transferred at a time. Accordingly, for example, the data X1 of the display data 104 is represented by the display dots x1 and x in FIG.
2, x3, x4. For this reason, the number of pulses of the display data transfer signal 103 output from the display controller 7 is, here, 120 pulses (= 48
0 ÷ 4).

Here, the display controller 7 includes the CPU 1
The number of output pulses 120 per line of the display data transfer signal 103 and the number of horizontal scanning lines (321+
N) is set in advance, and the position reading period (position reading device 102)
321 indicating the start line and the value (3
21 + N).

The display controller 7 supplies the display data 104 and the display data transfer signal 103 to the display device 5 periodically and synchronously with each other in order to display the data on the display device 5, and displays the display data for one line. When the transfer of the data 104 is completed, a horizontal scanning signal 105 is output. Thus, the display device 5 selects the number-th pulse line of the supplied horizontal scanning signal 105, and displays one line of display data 104 transferred to the selected line. Further, the display device 5 counts the horizontal scanning signal 105, and after displaying the display data for 13 lines, inverts the polarity of the liquid crystal alternating signal 106 and counts the horizontal scanning signal 105 again from 0.

The display controller 7 and the display device 5 repeat the above-mentioned operations, and change the (321+
N) The display control signal is output.

Further, after outputting the (321 + N) pulse of the horizontal scanning signal 105, the display controller 7 transfers the display data 104 of the line Y1, which is the first line of the display screen, to the display device 5, and outputs the Y1 of the horizontal scanning signal 105. The frame signal 107 is supplied to the display device 5 in synchronization with the pulse. Therefore, the display device 5 returns the display scanning to the first line Y1 by the frame signal 107, and outputs the frame signal 1 even if the horizontal scanning signal 105 after the line Ymax is supplied.
Until 07 is supplied, scanning is performed outside the display area 101 (that is, the position reading area 102), and the inside of the display area 101 is not affected.

By inputting such a display control signal and display data, the display device 5 displays 480 dots horizontally and 320 lines vertically.

The position reading period signal generation circuit 9 counts the horizontal scanning signal 105,
When the counted value reaches 321, the position reading period signal 108 is set to a low level output, the horizontal scanning signal 105 is counted, and the value (321 + N) previously set by the CPU 1 is calculated. The low-level position reading period signal 108 is supplied to the signal fixing circuit 8 and the period notification circuit 10 until).

Therefore, the signal fixing circuit 8 fixes the level of the display data transfer signal 103 and the horizontal scanning signal 105 supplied from the display controller 7 during the period when the position reading period signal 108 is at the low level. And the horizontal scanning signal 105 are at a low level. Therefore, the horizontal scanning signal 105 supplied from the signal fixing circuit 8 to the display device 5 becomes a signal 110 shown in FIG.

Further, the period notification circuit 10 generates a position reading notification signal 109 having a predetermined pulse width from the falling edge when the supplied position reading period signal 108 becomes low level, and supplies it to the CPU 1. Therefore, the CPU 1 recognizes the start of the position reading area 102 from the position reading notification signal 109, interrupts the processing that has been performed at that time, and reads the position from the tablet 2. The position reading notification signal 109 may be, specifically, an interrupt signal to the CPU 1. As a result, the output signal of the tablet 2 becomes a signal 111 shown in FIG.

The noise generated by the electrostatic coupling between the display device 5 and the tablet 2 is generated at the level change point between the horizontal scanning signal 110 and the liquid crystal alternating signal 106 as described in the above-mentioned prior art. , Liquid crystal alternating signal 106
The noise becomes maximum at the level change point. Most of the liquid crystal alternating signal 106 is generated in the display device 5 by counting the horizontal scanning signal 110.
For this reason, when this type of display device 5 is used, the liquid crystal alternating signal 1 is used as long as the horizontal scanning signal 110 does not change.
06 does not change. In this embodiment, this type of display device 5 is used. In the case of a type in which a liquid crystal alternation signal 106 is generated externally and supplied to the display device 5, an input signal to an external liquid crystal alternation generation unit is fixed at a signal level as in this embodiment, thereby realizing this implementation. The same effect as in the embodiment can be obtained.

As described above, in the first embodiment, the CPU 1 recognizes the start of the position reading area 102 based on the supply of the position reading notification signal 109 even when executing other processing. Further, the signal fixing circuit 8 fixes the levels of the display data transfer signal 103 and the horizontal scanning signal 105 during the scanning of the position reading area 102, so that the horizontal scanning signal 110 is obtained and the level change point is Of course, since no signal change point of the liquid crystal alternating signal 106 occurs, the scanning period of the position reading area 102 is not actually performed. However, for the sake of convenience, the scanning period of the display area 101 is opposed to the scanning period. Therefore, it is possible to completely avoid noise in the above expression), and it is possible to perform accurate position reading.

Here, in the display area 101, the required number of lines is 320, whereas
The reason why the line 321 is provided as one line will be described.

When the number of lines in the display area 101 is set to 320, the scanning of the display area 101 ends, and when the signal fixing circuit 8 masks the horizontal scanning signal 105 with the line 321, the display device 5 selects the line 320. And display it. As a result, the line 320 continues displaying for a longer time than the other lines, and the display device 5
Is a liquid crystal display device, the luminance of the line 320 is higher than that of the other lines.

However, as in the first embodiment, the number of lines in the display area 101 is 321 and the last line 3
By setting 21 outside the display screen of the display device 5, even if this line 321 is selected and displayed for a long time, it does not appear on the display screen, and when the scanning of the display area 101 is completed, this display area is displayed. 32 on the display screen of 101
All 0 lines are not selected (not displayed), and all these lines have uniform luminance.

FIG. 3 is a block diagram showing a specific example of the position reading period signal generating circuit 9 in FIG. 1, wherein reference numeral 17 denotes a vertical fixed period start register, 11 denotes a vertical counter,
2 is a vertical fixed period end register, 13 and 14 are comparison circuits, 15 is a vertical counter reset signal generation circuit, 16
Is a vertical position reading period signal generation circuit, 112 and 113 are comparison result signals, and 114 is a vertical counter reset signal.

In FIG. 5, as described with reference to FIG.
A value 321 indicating the start line of 02 is written, and a value (321 + N) indicating the last line is also written in the vertical fixed period end register 12 in advance. This N value is the number of lines of the position reading area 102 (the time width of the position reading period signal in FIG. 2A). The number of lines in the position reading area 102 can be set arbitrarily within a range in which flickering of the screen of the liquid crystal display device 5 (FIG. 1) and a decrease in luminance are considered, and is usually set to a range until the frame frequency becomes about 70 Hz. be able to.

The vertical counter 11 is a display controller 7
The horizontal scanning signal 105 from FIG. 1 is counted. The counter value is compared with the set value 321 of the vertical fixed period start register 17 by the comparison circuit 13, and when both are equal, a comparison result signal 112 is generated and supplied to the vertical position reading period signal generation circuit 16. As a result, the position reading period signal 108 output from the vertical position reading period signal generation circuit 16 becomes low level.

The count value of the vertical counter 11 is
The comparison circuit 14 compares the value (321 + N) set in the vertical fixed period end register 12 with the value (321 + N). If the two become equal, the comparison circuit 14 generates a comparison result signal 113 and the vertical position reading period signal generation circuit 16 It is supplied to the vertical counter reset signal generation circuit 15.

Therefore, the vertical position reading period signal generation circuit 1
6 indicates that the position reading period signal 108 is set to a high level at the timing of the comparison result signal 113,
To indicate that the scanning period has ended. The vertical counter reset signal generation circuit 15 outputs the vertical counter reset signal 114 at the timing of the comparison result signal 113.
, Thereby clearing the vertical counter 11 to zero. Thereby, the horizontal scanning for one frame is completed, and the same operation is repeated by moving to the next frame.

The period in which the position reading period signal 108 obtained as described above is at the low level is the period of the position reading area 102 shown in FIG.

Therefore, for example, in FIG.
Assuming that the frequency of 05 is 30 KHz, the time required to display the liquid crystal display screen, which is the display area 101 of 320 lines, is 320 × 1 / (30 × 10 ³ ) = 10.7.
msec and the frame frequency is 70 Hz,
The frame frequency is 1/70 sec, that is, 14.3 ms
ec. Therefore, the scanning period of the position reading area 102 can be arbitrarily set in the range of 14.3-10.7 = 3.6 msec.

As described above, a period in which the level of the display control signal is stable can be set as a sufficiently long scanning period of the position reading area 102, so that the position information can be read N times in the same period, and the accuracy of the position information can be improved. improves.

Each circuit can be easily constituted by a general-purpose TTL or LSI.

FIG. 4 is a block diagram showing a specific example of the signal fixing circuit 8 shown in FIG. 1. Reference numerals 18 and 19 denote AND elements.

In the figure, the AND element 19 fixes the display data transfer signal 103 to a low level while the position reading period signal 108 is at a low level, and
5 is supplied to the display device 5. The AND element 18
Indicates that the horizontal scanning signal 105 is fixed at a low level while the position reading period signal 108 is at a low level,
The reference numeral 10 is supplied to the display device 5.

As described above, the display data transfer signal 11
5 and the horizontal scanning signal 110 are the position reading period signal 108
During the low level period.

The display device 5 is supplied with these low-level display control signals, so that the position reading area 102 is displayed.
Is set. The frame signal 107 from the display controller 7 is supplied to the display device 5 without passing through the signal fixing circuit 8.

FIG. 5 is a view for explaining the operation of the second embodiment of the position reading apparatus according to the present invention. Reference numeral 116 denotes a position reading area, and 117 denotes a position reading period signal.

In the first embodiment described above, the position reading area 102 is provided continuously in the vertical direction of the display area 101 with respect to the screen of the display device 5.
In the embodiment, the position reading area is provided in the horizontal scanning direction of the display area 101. However, the second embodiment has the same overall system configuration as the first embodiment shown in FIG.

FIG. 5A schematically shows the period of one frame in association with the display area of the display device 5.
A position reading area 116 is set in the horizontal direction of the display area 101, and the time required to scan the display area 101 and the position reading area 116 is one frame.

As shown in FIG. 5A, the position reading area 1
By setting 16, since the level of the horizontal scanning signal 105 and the liquid crystal alternating signal 106 does not change in this area 116, it is possible to avoid noise generated by the horizontal scanning signal 105 and the liquid crystal alternating signal 106. it can. Since the noise from the substrate is reduced, the display data transfer signal 103 is also
The output may be fixed.

The operation for realizing this will be described below.

In the second embodiment, as shown in FIG. 5A, dots N1
5 to Nmax, and the position reading period signal 117 is set to a low level during the scanning period of the position reading region 116 as shown in FIG. 5B.

The display data transfer signal 103 is fixed at a low level during the low level period of the position reading period signal 117, and the display data transfer signal 121 shown in FIG.
Becomes As the display data transfer signal 121, the display data transfer signal 103 is supplied during a period included in the display area 101 (FIG. 5A) of each line, and the position reading area 116 is provided.
In the period included in FIG. 5A, the display data transfer signal 103 is not supplied. As a result, during the position reading area 116, the display data transfer signal 103 and the liquid crystal alternating signal 106 are fixed, and no noise is generated in the tablet. Therefore, effects similar to those of the first embodiment can be obtained.

The provision of the position reading area 116 in the horizontal scanning direction of the display area 101 is more advantageous than the first embodiment in terms of the flickering of the screen of the liquid crystal display device and the contrast ratio.

FIG. 6 is a block diagram showing a specific example of the position reading period signal generating circuit 9 (FIG. 1) according to the second embodiment. Reference numeral 190 denotes a horizontal fixed period start register;
20 is a horizontal counter, 21 is a horizontal fixed period end register, 22 and 23 are comparison circuits, 24 is a horizontal counter reset signal generation circuit, 25 is a horizontal position reading period signal generation circuit, 118 and 119 are comparison result signals, and 120 is This is a horizontal counter reset signal.

In FIG. 5 and FIG.
Counts the display data transfer signal 103 from the display controller 7 (FIG. 1). From the resolution of the display device 5 (FIG. 1), a value 120 equal to the number of pulses for one line in the display area 101 of the display data transfer signal 103 is preset in the horizontal fixed period start register 190, and the horizontal fixed period end register is set. 21 is a value (1) indicating the last pulse of the display data transfer signal 103 supplied to the position reading area 116.
20 + N ') is set.

Other than the above, the position reading period signal generation circuit 9 shown in FIG. 3 is the same as the position reading period signal generation circuit 9 shown in FIG.
17 is output. The position reading period signal 117 is at a low level during the period of the position reading area 116 in FIG.

FIG. 7 is a block diagram showing a specific example of the signal fixing circuit 8 (FIG. 1) for defining the position reading area 116 in the second embodiment. Reference numeral 26 denotes an AND element.

In FIG. 5 and FIG.
5 shows that the display data transfer signal 103 is fixed at a low level while the position reading period signal 117 from the position reading period signal generation circuit 9 shown in FIG. 6 is at a low level.
It is supplied to the display device 5 as the display data transfer signal 121 shown in (b)). That is, by sending a low-level display control signal to the display device 5, the period of the position reading area 116 is set. The frame signal 107 and the horizontal scanning signal 105 from the display controller 7 (FIG. 1) are supplied to the display device 5 without passing through the signal fixing circuit 8.

FIG. 8 is an explanatory view of the operation of the third embodiment of the position reading apparatus according to the present invention. Reference numeral 122 denotes a position reading area, 117 denotes a horizontal position reading period signal, and 108 denotes a vertical position reading period signal. The same reference numerals are given to portions corresponding to the above-mentioned drawings.

In the third embodiment, the horizontal of the display area,
The position reading area is set in the vertical scanning direction.

FIG. 8A schematically shows the period of one frame in association with the display area 101 of the display device 5. The position reading area 122 is set in the horizontal and vertical directions of the display area 101. The time required to scan the display area 101 and the position reading area 122 is defined as one frame.

The system configuration of the third embodiment is the same as that of the first embodiment shown in FIG.

The position reading period signal generation circuit 9 in the third embodiment includes a position reading period signal generation circuit 9 in the vertical scanning direction shown in FIG. 3 and a reading period signal generation circuit 9 in the horizontal scanning direction shown in FIG. As shown in FIG. 8B, the circuit 9 includes lines Y0, Y1,... Ymax and M1 to Mmax dots assumed in the horizontal scanning direction position reading area 122 in the horizontal scanning direction. A horizontal position reading period signal 117 that is low during the period of the position reading area 122 and a vertical position reading period signal 108 that is low during the period of the position reading area 122 in the vertical scanning direction are generated.

The horizontal position reading period signal 117 and the vertical position reading period signal 108 are supplied to the signal fixing circuit 8 in FIG. 1 in the third embodiment.

FIG. 9 is a block diagram showing a specific example of the signal fixing circuit 8 (FIG. 1) in the third embodiment.
7 and 28 are AND elements.

8 and 9, the AND element 27
Fixes the display data transfer signal 103 to a low level during a period in which the horizontal reading period signal 117 and the vertical position reading period signal 108 are at a low level, and supplies the display data transfer signal 103 to the display device 5 as a display data transfer signal 121. The AND element 28 fixes the horizontal scanning signal 105 to a low level while the vertical position reading period signal 108 is at a low level, and supplies the horizontal scanning signal 105 to the display device 5 as a horizontal scanning signal 110.
The low-level display data transfer signal 121 and the horizontal scanning signal 110 cause the position reading area 12 shown in FIG.
2 is set.

Although the display data transfer signal 103 and the horizontal scanning signal 105 have been described as being fixed at a low level,
The same effect can be obtained even when the high level is fixed.

As described above, also in the third embodiment, a position reading area for performing position reading is provided outside the display area, and during that period, the display control signal, which is a source of noise to the tablet, is kept at a constant level. Since the output is fixed, noise on the tablet can be completely avoided, and good position reading can be performed. Further, the start of the position reading area is determined by the CPU.
Therefore, the CPU can perform other processing until notified of the position reading area, thereby greatly improving the processing efficiency of the CPU.

FIG. 10 shows a fourth embodiment of the position reading apparatus according to the present invention.
FIG. 29 is a configuration diagram showing an embodiment of the present invention, in which 29 is a vertical transparent resistance film, 30 is a horizontal transparent resistance film, 31 is an anode-side horizontal electrode, 32 is a cathode-side horizontal electrode, and 33 is an anode-side vertical electrode. , 34 are vertical electrodes on the cathode side, 35 to 38 are switches, 39 is a press signal detection circuit, 40 is a noise removal circuit,
41 is a press signal notification circuit, 42 is a switch, 43 and 44
Is a resistor, 100 is a tablet press detection signal, 401 is a pen state signal, 402 is a horizontal reading terminal, 403 is a vertical reading terminal, and 404 is a press signal.

In the drawing, the tablet 2 has a structure in which a vertical transparent resistance film 29 and a horizontal transparent resistance film 30 are overlapped with a predetermined minute gap therebetween. Numerals 30 have a structure in which they are superposed at uniform minute intervals. The press signal detection circuit 39 includes a switch 42 and a resistor 43.
Here, such a tablet 2 is connected to the display device 5.
Although it is assumed that the tablet 2 is integrated at a certain interval, the tablet 2 does not necessarily need to be provided on the display device 5.

The horizontal electrode 33 on the anode side of the horizontal transparent resistive film 30 and the vertical electrode 3 on the anode side of the vertical transparent resistive film 29
Reference numeral 1 designates that a positive power supply voltage VCC is supplied via switches 35 and 38, respectively, and the horizontal electrode 34 on the cathode side of the horizontal transparent resistive film 30 and the vertical transparent resistive film 29 The vertical electrode 32 on the cathode side is grounded via switches 36 and 37 and a common resistor 44, respectively. The horizontal read terminal 402 is grounded between the vertical electrode 32 of the vertical transparent resistive film 29 and the switch 36, and the vertical read terminal 403 is connected between the horizontal electrode 34 of the horizontal transparent resistive film 30 and the switch 37. Grounded.

The feature of the fourth embodiment is that when the pen is not pressed, only the switches 35 and 42 are in the ON state, and the pen is in a state in which the pen can be read. The point is that a press signal detection circuit 39 for detecting a press, a noise removal circuit 40, and a press signal notification circuit are provided.

That is, in the fourth embodiment, when corresponding to FIG. 1, the tablet 2 corresponds to the tablet 2 in FIG. 1, and the switches 35 to 38 correspond to the switch circuit 3 in FIG. In the fourth embodiment, the pressing signal detection circuit 39 is further connected to the ground between the horizontal electrode 34 of the horizontal transparent resistive film 30 and the switch 37.
A noise removing circuit 40 and a press signal notifying circuit 41 are provided, and when the pen is not pressed, the switch 3
6 to 38 are off, and the vertical transparent resistance film 29 and the horizontal transparent resistance film 30 are separated and insulated from each other. , No current flows. Therefore, no current flows through the resistor 43, and the press signal 404 is at a low level. The low-level press signal 404 is supplied to the press signal notifying circuit 41 via the noise removing circuit 40. Then, the press signal notification circuit 41 supplies the pen state signal 401 corresponding to the press signal 404 to the CPU 1, does not change the tablet press detection signal 100, and does not notify the CPU 1 of the pen press. For this reason, the CPU 1 can execute other processing without controlling the tablet 2.

In this state, when the pen is pressed, the vertical transparent resistance film 29 and the horizontal transparent resistance film 30 come into contact with each other at the point where the pen is pressed, and the switch 35 and the vertical transparent resistance An electric path is formed through the depression point of the film 29, the horizontal transparent resistance film 30, the switch 42, and the resistor 43, and a voltage is generated in the resistor 43. This is detected by the press signal detection circuit 39, and the high level press signal 404 is detected.
Is generated, and the pressing signal 404 is
After the noise is removed in step (1), the signal is processed by the press signal notification circuit 41 and supplied to the CPU 1 as a high-level pen state signal. At the same time, the press signal notification circuit 41 changes the tablet press detection signal 100, thereby
The PU 1 is notified that the pen has been pressed. CPU1
Receives this notification, it starts the operation of reading the position of the pen depression point, as described later.

The operation of reading the coordinates of the pen pressing point of the tablet 2 in the fourth embodiment will be described in detail. The processing operation of the signal read from the tablet 2 will be described in each of the previous embodiments. The operation is the same as that described above.

When the tablet 2 is pressed by a pen (not shown), the vertical transparent resistance film 29 and the horizontal transparent resistance film 30 come into contact with each other at the pen pressing point. When receiving the notification of the pen press on the tablet 2 as described above, the CPU 1 first closes the switches 37 and 38 (hereinafter referred to as the ON state) in order to read the horizontal coordinate position of the pen press point. . As a result, the positive power supply voltage VCC is applied to the horizontal electrode 33 on the cathode side of the horizontal transparent resistive film 30,
When the horizontal electrode 34 on the cathode side is grounded via the switch 37 and the resistor 44, a current flows from the horizontal electrode 33 side to the horizontal electrode 34 side in the horizontal transparent resistive film 30.

At this time, if the pen is pressed down, the vertical transparent resistance film 29 is in contact with the pen pressed point of the horizontal transparent resistance film 30, so that the horizontal reading terminal 40 is pressed.
2 outputs a divided voltage of the horizontal transparent resistive film 30 at the contact point. This divided voltage is processed by the A / D converter 4 in FIG. 1 and converted into digital data, and is supplied to the CPU 1. The CPU 1 is processed by the A / D converter 4, converted into digital data, and supplied to the CPU 1. The CPU 1 performs arithmetic processing on the digital data to generate a coordinate point in the horizontal direction when the pen is pressed.

Next, in order to read the vertical coordinate position when the pen is pressed, the CPU 1 closes the switches 37 and 38 (hereinafter, referred to as off state) and turns on the switches 35 and 36. As a result, the positive power supply voltage V is applied to the vertical electrode 31 on the anode side of the vertical transparent resistance film 29.
CC is applied, and the vertical electrode 32 on the cathode side
6. By being grounded via the resistor 44, a current flows from the vertical electrode 31 side to the vertical electrode 32 side in the vertical direction transparent resistance film 29. At this time, a divided voltage at the point of contact with the horizontal transparent resistive film 30 by pressing the pen on the vertical transparent resistive film 29 is obtained at the vertical read terminal 403, and this voltage is supplied to the A / D converter 4 in FIG. The data is processed and converted into digital data, and supplied to the CPU 1. The CPU 1 performs arithmetic processing on the digital data to generate a coordinate point in the vertical direction when the pen is pressed.

Next, the details of the noise removing circuit 40 which is a feature of the fourth embodiment will be described.

The noise removing circuit 40 can be constituted by a simple low-pass filter circuit as shown in FIG. According to this, as shown in FIG. 11B, the impulse noise generated at the changing point of the liquid crystal alternating signal 106 of the display device 5 is caused by the electrostatic coupling between the display device 5 and the tablet 2. 2 and is superimposed on the pressing signal 404.
Pass through zero. Accordingly, as shown in FIG. 11C, the level of the press signal 404 that has passed through the noise removal circuit 40 has changed from the time when the pen was pressed. The press signal 404 is formed into a waveform by the press signal notifying circuit 41 and supplied to the CPU 1 as the press signal 401. Thereby, C
PU1 avoids an erroneous press signal 404 generated by the liquid crystal alternating signal 106, and can surely recognize pen press.

In the fourth embodiment, the use of the tablet press detection signal 100 as an interrupt signal by the CPU 1 makes it possible to immediately recognize the occurrence of pen press.

This operation makes it possible to effectively utilize the processing capability of the CPU and to significantly reduce power consumption. In addition, as a signal which becomes a moving condition of the processing,
Tablet press detection signal 100 shown in FIGS. 1 and 10
And the position reading notification signal 109 are used.

In FIGS. 10 and 12, the CPU 1 sets the switches 35 and 42 to the ON state and the other switches to the OFF state, thereby setting the state to the pen state recognition wait state (step 201). Thereafter, until the pen down occurs, the CPU 1 can perform completely different processing (step 202) such as display control and power supply control.

When the pen-down occurs, the tablet press detection signal 100 is supplied to the CPU 1, and the CPU 1 temporarily suspends the other processes in the step 202 and permits the generation of the position reading notification signal 109 (step 203).

As described above, by notifying the CPU 1 of the pen down by hardware, the CPU 1 does not need to always recognize the pen down by software, and other processing (step 202) can be performed. Then, the CPU 1 can perform other processing (step 202) until the position reading notification signal 109 is notified.

When the position reading notification signal 109 is supplied to the CPU 1, the CPU 1 sets the horizontal coordinate reading processing and executes the horizontal coordinate reading processing (step 2) as described above.
04). As described with reference to FIG. 1, the CPU 1 converts the read horizontal coordinate voltage into digital data by the A / D converter 4 (Step 205), takes in the digital data, performs arithmetic processing, and generates the horizontal coordinate of the pen pressing point. (Step 206). Next, similarly, vertical coordinate reading processing (step 207) is performed, and the CPU 1 converts the read vertical coordinate voltage into digital data by the A / D converter 4 (step 208), takes in the data, and performs arithmetic processing. Generate vertical coordinates of the pen pressing point (step 20)
9).

When the series of coordinate reading processing is completed, the CPU 1 performs another processing (step 202) again.

As shown in FIG. 13, the CPU reads the high-level or low-level pen status signal 401 in the pen-down confirmation process (step 200) to confirm once again that the pen-down has occurred. Can be.

As described above, in the fourth embodiment, pen depression can be recognized with very little power consumption.
The CPU 1 can be released to other processing without occupying the CPU 1 for pen pressing recognition.

Further, similarly to the embodiment shown in FIG.
By using the signal fixing circuit 8, the position reading period signal generation circuit 9, and the period notification circuit 10, noise from the display device 5 can be completely avoided, and highly accurate position reading can be performed.

FIG. 13 shows a fifth embodiment of the position reading apparatus according to the present invention.
FIG. 2 is a configuration diagram illustrating the embodiment, wherein reference numeral 45 denotes a pen state recognition circuit.

In the fifth embodiment, a pen state recognition circuit 45 is used instead of the press signal notification circuit 41 in the fourth embodiment shown in FIG.

Since the operation of reading the coordinates of the pen pressing point on the tablet 2 in the fifth embodiment is the same as that of the previous embodiment, the pen state recognition circuit which is a feature of the fifth embodiment. The operation of 45 will be described with reference to FIGS.

When the pen is depressed, a series of position reading processing similar to that of the fourth embodiment shown in FIG. 10 is performed.
This series of processing includes a horizontal coordinate reading processing period 501 and a vertical direction reading processing period 502. Then, after such position reading processing, the process proceeds to the pen-up state recognition period 503, and the CPU 1 turns on the switches 35 and 42. At this time, if the pen is in the pressed state, the pressed signal 404 goes to a high level, the noise removal processing is performed by the noise removal circuit 40, and the signal is supplied to the pen state recognition circuit 45.

The pen state recognition circuit 45 recognizes that the pen is being pressed from the high-level press signal 404, and supplies the CPU 1 with the pen state signal 401 as a high level, for example. The CPU 1 validates the position information obtained by recognizing that the pen pressing is continued by the high-level pen state signal 401,
This is processed to calculate the pen pressing point on the tablet 2.

On the other hand, in the pen-up state, there is a minute gap between the vertical transparent resistance film 29 and the horizontal transparent resistance film 30, so that the vertical transparent resistance film 29 and the horizontal transparent resistance film 30 It is insulated, and no current flows between them. Therefore, the pressing signal 4 generated in the resistor 43
04 is at a low level, and the press signal 404 supplied to the pen state recognition circuit 45 via the noise removal circuit 40 is at a low level.

The pen state recognizing circuit 45 notifies the CPU 1 of the pen-up state by, for example, setting the pen state signal 401 to a low level. CPU
When receiving the notification, 1 determines whether the position information obtained immediately before is valid or invalid, performs the processing corresponding thereto, and ends the position reading processing.

A specific example of the operation of the fifth embodiment when pen-up actually occurs will be described with reference to FIG.

In FIG. 15, the operation within the broken line is the same as that of the fourth embodiment shown in FIG. 10 shown in FIG. 12, and when such a series of position reading processing is completed, the CPU 1 turns on the switches 35 and 42. Then, the other switches are turned off to set a pen state recognition processing state (step 210). After this setting, if the pen is in the pressed state, the pen state recognizing circuit 45 outputs a high-level pen state recognition signal 4.
01 is output, and the CPU 1
By detecting that the high level of 01 has been reached,
The process branches off by the pen-up determination process 211, and the reading process is continued by recognizing that the pen has been pressed. After the pen state recognition processing state (step 210) is set, if the pen is in the pen-up state, the CPU 1 executes the pen state recognition signal 4 during coordinate reading processing.
01 changes from the high level to the low level, thereby detecting that the pen is up, determining that the data read immediately before the pen up is invalid data, and discarding the read data (step 212). .

When the invalid data discarding process (step 212) is completed, the CPU 1 returns to the state of waiting for pen down recognition (step 213). It takes several msec from the detection of the pen press to the end of the coordinate position reading process,
When the pen-up operation is performed within a few msec, the resistance film 2
The contacts 9 and 30 are insufficient or non-contact, and at this time, the coordinate data read by the CPU 1 has poor reliability.

In order to avoid this, as described above, by detecting pen-up and executing the invalid data discarding process 212, the coordinates of the pen-pressed position with higher precision can be obtained without erroneous coordinate position reading. You can find points.

In the fifth embodiment, the pen state recognition processing (step 210) is performed at the end of the coordinate reading processing. However, the present invention is not limited to this. Also, pen state recognition processing (step 210)
Is executed once in the coordinate reading process in the fifth embodiment, but the number of times is not limited in the present invention.

FIG. 16 is a block diagram showing a sixth embodiment of the position reading apparatus according to the present invention.
1 is a power supply control circuit, 72 is a position reading period adjustment circuit, and the portion enclosed by a broken line is the same as that described in the above embodiment, and the portions and signals corresponding to the above-mentioned drawings have the same reference numerals. And duplicate explanations are omitted. In the figure, a power supply unit 70 supplies a voltage applied to the liquid crystal.

A feature of the sixth embodiment is that when the pen is not pressed, the position reading period is not provided to control the liquid crystal application voltage low, thereby reducing power consumption.

That is, in the sixth embodiment, when the pen state signal 401 is supplied from the pen state recognition circuit 45 to the position reading adjustment circuit 72 and the power supply control circuit 71, and the pen is pressed, the sixth embodiment will be described. When the position reading period is set and the pen reading is not performed and the position reading process is not performed, the position reading period adjustment circuit 72 sets so as not to provide the position reading period. When the position reading period is not set, the period of one frame for displaying one screen is shortened, and the shading of the screen changes. Therefore, the shading of the screen does not change in advance from the power supply adjustment circuit 72 at the same time as the position reading period disappears. A voltage is applied to the liquid crystal display device 5. This applied voltage is lower than the voltage applied to the liquid crystal display device when the position reading period is set.

As described above, in the sixth embodiment, the voltage applied to the liquid crystal display device 5 can be reduced until the pen depression is detected, thereby reducing power consumption.

Next, the operation of the position reading period adjustment circuit 72 which is a feature of the sixth embodiment will be described with reference to FIG. 73 is a position reading period adjustment register, and 74 is a selector. The portion surrounded by the broken line is the same as that described in the above embodiment.

In the state where the pen is pressed to perform position reading, the pen state signal 401 is at the high level,
The selector 74 selects the value of the vertical fixed period end register 12 and supplies it to the comparison circuit 14. At this time, a series of processes described in the third embodiment are performed, and the low-level position reading period signal 108 is supplied to the signal fixing circuit 8.

On the other hand, when the pen is not pressed, the pen state signal 401 is at the low level, and the selector 74 selects the value of the position reading period adjustment register 73 and supplies it to the comparison circuit 14. Here, the value of the position reading period adjustment register 73 is set to the same value as that of the vertical fixed period start register 17 in advance. Since the value of the position reading period adjustment register 73 and the value of the vertical fixed period start register 17 are the same, the comparison circuits 13 and 14 also compare the same value, and the comparison result signals 112 and 113
Are the same signal, and the vertical position reading period signal generation circuit 16
Supplied to The vertical position reading period signal generating circuit 16 compares the comparison result signals 112 and 1 indicating the start and end of the mask period.
Since 13 has the same value, a high-level position reading period signal 108 is supplied to the signal fixing circuit 8. Since the position reading period signal is at a high level in the signal fixing circuit 8, the liquid crystal driving signal is not fixed.
Is supplied as it is.

The power supply control circuit 71 includes a selector 75 as shown in FIG. Reference numeral 80 denotes a voltage when the pen is pressed, and 81 denotes a voltage when the pen is raised.

Here, the voltage 80 at the time of pen pressing and the voltage 81 at the time of pen up are set in advance. Pen pressing voltage 8
0 is a voltage several volts higher than the pen-up voltage 81.

In a state where the pen is pressed, the pen state signal 401 is at the high level, and the selector 75 selects the voltage of the pen pressing voltage 80 and supplies it to the liquid crystal display device 5.

On the other hand, when the pen is not pressed down, the pen state signal 401 is at the low level, and the selector 75 selects the pen-up voltage 81 and supplies it to the liquid crystal display device 5.

As described above, in the sixth embodiment, the noise at the time of position reading is avoided by monitoring the state of pen pressing and generating the position reading period and changing the voltage applied to the liquid crystal display device 5. Meanwhile, the power consumption can be further reduced.

In the present invention, the description has been made on the assumption that the display density of the display device 5 changes by adding the position reading period. However, for a display device in which the display density does not change, the power supply control circuit 71 is omitted and the correspondence is eliminated. can do.

The embodiments of the present invention have been described above, but the present invention is not limited to only such embodiments. For example, in each embodiment, the liquid crystal display device is ST
Although an N-type liquid crystal display device is used, the present invention is not limited to this, and a TFT-type liquid crystal display device may be used,
Further, a display device other than the liquid crystal display device may be used.

Although the display device and the tablet are integrated as a system configuration, there is no problem even if the display device and the tablet are separated.

In each embodiment, the resolution of the liquid crystal display device is 480 dots in the horizontal resolution and 32 in the vertical resolution.
Although the number of lines is 0, the present invention is not limited to this, and accordingly, the horizontal signal fixed period start register 10, the horizontal signal fixed period end register 11, the vertical direction fixed period start register 19, and the vertical direction fixed period end register 21 It is clear that this can be achieved by changing the set value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a position reading device according to the present invention.

FIG. 2 is an explanatory diagram of the operation of the first embodiment shown in FIG.

FIG. 3 is a block diagram showing a specific example of a position reading period signal generation circuit in FIG. 1;

FIG. 4 is a block diagram showing a specific example of a signal fixing circuit in FIG. 1;

FIG. 5 is an explanatory diagram of an operation of a second embodiment of the position reading device according to the present invention.

FIG. 6 is a block diagram showing a specific example of a position reading period signal generation circuit in a position reading device according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a specific example of a signal fixing circuit in a position reading device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of an operation of a third embodiment of the position reading device according to the present invention.

FIG. 9 is a block diagram showing a specific example of a signal fixing circuit in a third embodiment of the position reading device according to the present invention.

FIG. 10 is an explanatory diagram of the operation of the fourth embodiment of the position reading device according to the present invention.

11 is an explanatory diagram showing a specific example of a noise removing circuit in FIG. 10 and its operation.

FIG. 12 is a flowchart showing a specific example of the operation of the fifth embodiment of the position reading device according to the present invention.

FIG. 13 is an explanatory diagram of a system showing a third embodiment according to the present invention.

FIG. 14 is a timing chart showing an operation of a specific example according to the third embodiment of the present invention.

FIG. 15 is a flowchart showing an operation of a specific example in the third embodiment shown in FIG. 13;

FIG. 16 is an explanatory diagram of an operation of a position reading device according to a sixth embodiment of the present invention.

FIG. 17 is a block diagram showing a specific example of a position reading period adjustment circuit in FIG. 16;

18 is a block diagram showing a specific example of a power supply control circuit in FIG.

FIG. 19 is an explanatory diagram of an operation of an example of a conventional position reading device.

[Description of numbers]

 2 tablet, 3 switch circuit, 4 A / D converter, 5 display device, 7 display controller, 8 signal fixing circuit, 9 position reading period signal generation circuit, 10 period recognition circuit, 71 position Reading period adjustment circuit, 72: power supply control circuit, 102: position reading area, 116: position reading area.

Continued on the front page (72) Inventor Yutaka Tsunada 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi Image Information System (72) Inventor Tetsuya Suzuki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Yokohama Hitachi, Ltd. In the information system

Claims (2)

[Claims] 1. A position reading device comprising a display device, a display controller for generating a display device signal for controlling the display device, a tablet as input means, and an A / D converter for converting an output period signal of the tablet into position information. In the above, when detecting the press of the tablet, a position reading period for converting the output signal of the tablet to the position information is provided outside the display period of the display device, and the position reading period is output from the display controller. Wherein the level of the display control signal among the display control signals is fixed to avoid generation of noise components in the output signal of the tablet, and the position information can be generated. Reader. 2. A position reading device comprising a display device, a display controller for generating a display device signal for controlling the display device, a tablet as input means, and an A / D converter for converting an output period signal of the tablet into position information. In the above, when the press of the tablet is detected, outside the display period of the display device, a position reading period for converting the output signal of the tablet into the position information is provided, and the position reading period,
Of the display control signals output from the display controller, the level of the drive signal of the display device is fixed, avoiding a noise component from being mixed in the output signal of the tablet, and enabling the position information to be generated, A position reading device characterized in that the applied voltage applied to the display device is changed while the tablet is being pressed to reduce power consumption.