Abstract:
The present invention is directed to a display device such as a liquid crystal display including: a horizontal clock counter and a vertical clock counter which count each clock signal every horizontal cycle and every vertical cycle for a valid data period of a data enable input signal; and an input signal generating section for holding a count value and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device which is obtained at that time by utilizing a count value held at a last time for a next horizontal cycle or a next vertical cycle, the display device being applicable to the driver IC and the driving circuit which can be used for the display device having various resolutions.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a display device such as a liquid crystal display and an interface circuit for the display device.  
           [0002]    [0002]FIG. 6 is a diagram showing the structure of a display device such as a liquid crystal display. In FIG. 6, reference numeral  1  denotes a display screen such as a liquid crystal panel, reference numeral  2  denotes a driving circuit  1  such as a scanning line driving circuit, reference numeral  3  denotes a driving circuit  2  such as a signal line driving circuit, reference numeral  4  denotes a control circuit for generating input signals of the scanning line driving circuit  2  and the signal line driving circuit  3 , and reference numeral  5  denotes a power source section for generating reference voltages of a circuit system.  
           [0003]    In the structure of the electric circuit of the display device, a signal input from the outside (an input signal in the control circuit  4 ) includes a clock input signal, a video data input signal, a data enable input signal and other input signals for control (a horizontal synchronizing input signal, a vertical synchronizing input signal and the like). The data enable input signal indicates a valid data period in the video data input signal for a time base, and usually represents a voltage level of H for the valid data period and a voltage level of L for a period other than the valid data period.  
           [0004]    [0004]FIG. 7 is a voltage waveform diagram showing a signal input to the control circuit  4  every horizontal cycle. In FIG. 7, an axis of abscissa denotes an elapsed time, reference numeral  6  denotes a horizontal synchronizing input signal, reference numeral  7  denotes a data enable input signal, reference numeral  8  denotes a clock input signal, reference numeral  9  denotes a video data input signal, reference numeral  10  denotes a valid data period in the video data input signal, 1CLK denotes a cycle of the clock input signal  8 , 1H denotes a cycle of the horizontal synchronizing input signal, an arrow of the clock input signal represents an active edge (a falling edge in the drawing) of the clock input signal  8 , the blank portion of the video data input signal  9  represents a valid data period, the oblique line portion of the video data input signal represents an invalid data period, and m represents a screen size (resolution) in a horizontal direction. A voltage level of L in the horizontal synchronizing input signal  6  indicates a reset period, that is, a period in which there is no valid data.  
           [0005]    [0005]FIG. 8 is a voltage waveform diagram showing a signal to be input to the control circuit  4  every vertical cycle. In FIG. 8, an axis of abscissa denotes an elapsed time, the reference numeral  11  denotes a vertical synchronizing input signal, 1H denotes a cycle of a horizontal synchronizing input signal, 1V denotes a cycle of the vertical synchronizing input signal, the blank portion of a video data input signal represents a valid data period, the oblique line portion of the video data input signal represents an invalid data period, and n denotes a screen size (resolution) in a vertical direction. A voltage level of L in the vertical synchronizing input signal  11  indicates a reset period, that is, a period in which there is no valid data.  
           [0006]    As the output signal of the control circuit  4 , moreover, a clock signal and a data signal other than the clock signal are generated to be used for the input signal of a driver IC and a driving circuit which generates a signal for driving the control circuit  4 , that is, the scanning line driving circuit  2  and the signal line driving circuit  3 . The clock signal implies a clock signal to be used in the scanning line driving circuit  2  and the signal line driving circuit  3  (a vertical clock output signal in the scanning line driving circuit  2  and a horizontal clock output signal in the signal line driving circuit  3 ), respectively. The data signal other than the clock signal implies a video data signal (a horizontal video data output signal) and a control signal other than the video data signal (a horizontal start output signal, a vertical start output signal, a horizontal latch output signal, a horizontal driving voltage polarity control output signal and the like).  
           [0007]    However, the kind of the display device is increased with the diversification of the screen size and the resolution in the display device. Consequently, a control circuit  4  for generating a signal to be input to the driver IC and the driving circuit which generate a signal for driving a display screen or a part of the control circuit should be separately developed and fabricated to have a circuit for generating a signal having a timing relationship matched to each kind of the display device. For this reason, a period for the development and a cost of the development become important problems.  
           [0008]    In other words, a conventional control circuit or a part of the control circuit can be operated with values of m and n which are uniquely determined for each kind of the display device in FIGS. 2 and 3. Therefore, there is a problem in that the control circuit or a part of the control circuit cannot be used when m and n are not equal to set values or are changed during the display operation.  
           [0009]    It is an object of the present invention to provide a display device such as a liquid crystal display and an interface circuit for the display device which can solve the above-mentioned problems and implement an interface circuit for a display device capable of optionally changing a display size (resolution) corresponding to a display screen mode, thereby shortening a period for development and reducing a cost of the development.  
           [0010]    In case where the function of optionally changing the display size (resolution) in a display screen mode is to be provided in the prior art, software and hardware of a system for generating an input signal in the display device should be developed. Therefore, there is a problem in that the development and fabrication should be separately carried out for each system.  
           [0011]    It is another object of the present invention to provide a display device such as a liquid crystal display and an interface circuit for the display device which can solve the above-mentioned problem, can shorten a period for development and reduce a cost of the development and has the function of easily changing an optional display size (resolution) in a display screen mode by adding a simple circuit.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device which have the function of counting a valid data period of a data enable input signal every horizontal cycle and every vertical cycle, holding a count value and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device which is obtained at that time by utilizing a count value held last time for a next horizontal cycle or a next vertical cycle so as to be applicable to the driver IC and the driving circuit which can be used for the display unit having various resolutions, thereby solving the above-mentioned problems to shorten a period of development and to reduce a cost of the development.  
           [0013]    The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device which have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a data enable input signal corresponding to a display screen mode selected at that time, counting the valid data period of the data enable input signal every horizontal cycle and every vertical cycle, holding a count value and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device which is obtained at that time by utilizing a count value held last time for a next horizontal cycle or a next vertical cycle, and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.  
           [0014]    The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a data enable input signal corresponding to a display screen mode selected at that time and simultaneously recognizing a value of the resolution in response to a selecting input signal to generate an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.  
           [0015]    The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a video data input signal corresponding to a display screen mode selected at that time and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.  
           [0016]    These objects as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings. 
       
    
    
     BRIEF EXPLANATION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a functional block diagram for showing a structure of the circuit of a control circuit or a part of the control circuit in a display device of embodiment 1 of the present invention;  
         [0018]    [0018]FIG. 2 is a functional block diagram  1  for showing a structure of the circuit of a control circuit or a part of the control circuit in a display device of embodiment 2 of the present invention;  
         [0019]    [0019]FIG. 3 is a functional block diagram  2  for showing a structure of the circuit of a control circuit or a part of the control circuit in a display device of embodiment 2 of the present invention;  
         [0020]    [0020]FIG. 4 is a functional block diagram  1  for showing a structure of the circuit of a control circuit or a part of the control circuit in a display device of embodiment 3 of the present invention;  
         [0021]    [0021]FIG. 5 is a functional block diagram  2  for showing a structure of the circuit of a control circuit or a part of the control circuit in a display device of embodiment 2 of the present invention;  
         [0022]    [0022]FIG. 6 is an explanatory view showing a whole of the conventional display device;  
         [0023]    [0023]FIG. 7 is a wave form chart illustrating a relation of input part at each of the horizontal period in a control circuit of the conventionally used display device; and  
         [0024]    [0024]FIG. 8 is a wave form chart illustrating a relation of input part at each of the vertical period in a control circuit of the conventionally used display device. 
     
    
     DETAILED DESCRIPTION  
     Embodiment 1  
       [0025]    [0025]FIG. 1 is a diagram showing, for each functional block, the structure of a control circuit provided in a display device or a part of the control circuit (an interface circuit) according to an EMBODIMENT 1 of the present invention. In FIG. 1, reference numeral  12  denotes a horizontal clock counter for counting a clock number for a valid data period for each horizontal cycle, that is, a circuit section for counting a resolution in a horizontal direction, reference numeral  13  denotes a vertical clock counter for counting a data enable input signal  7  as a clock signal for a valid data period for each vertical cycle, that is, a circuit section for counting a resolution in a vertical direction, reference numeral  14  denotes a horizontal clock count memory for holding a value counted in a last stage for a predetermined period or all the time, reference numeral  15  denotes a vertical clock count memory for holding a value counted in a last stage for a predetermined period or all the time, reference numeral  16  denotes an input signal generating section a driver IC and a driving circuit, reference numeral  17  denotes a horizontal clock count signal indicative of a counted value, reference numeral  18  denotes a vertical clock count signal indicative of a counted value, reference numeral  19  denotes a signal indicative of a counter value holding the horizontal clock count signal  17  for a predetermined period or all the time, reference numeral  20  denotes a signal indicative of a counter value holding the vertical clock count signal  18  for a predetermined period or all the time, reference numeral  21  denotes a plurality of signals input from the outside, and reference numeral  22  denotes a plurality of signals output to the outside which are input to the driver IC and the driving circuit. In some cases, the input signal generating section  16  includes a conventional control circuit or a part of the conventional control circuit.  
         [0026]    First of all, the horizontal synchronizing input signal  6 , the data enable input signal  7  and the clock input signal  8  in FIG. 7 are input to the horizontal clock counter  12  in FIG. 1, thereby counting a valid data period for each horizontal cycle up to a value of m by a clock as a unit and outputting a result as the horizontal clock count signal  17 . In response to the horizontal clock count signal  17 , the horizontal clock count memory  14  holds the value of m for a predetermined period or all the time and outputs the value of m as the horizontal clock count signal  19 .  
         [0027]    Similarly, the data enable input signal  7  and the vertical synchronizing signal  11  in FIG. 8 are input to the vertical clock counter  13 , thereby counting a valid data period for each vertical cycle up to a value of n in a clock unit and outputting a result as the vertical clock count signal  18 . In response to the vertical clock count signal  18 , the vertical clock count memory  15  holds the value of n for a predetermined period or all the time and outputs the value of n as the vertical clock count signal  20 .  
         [0028]    As described above, the horizontal clock count signal  19  and the vertical clock count signal  20  which are output from the horizontal clock count memory  14  and the vertical clock count memory  15  and a plurality of input signals  21  in the input signal generating section  16  are input to the signal generating section  16 . Consequently, the input signal generating section  16  recognize the values output in the last stage (the values of m and n in FIGS. 7 and 8) to generate a signal to be input to the driver IC and the driving circuit corresponding to a resolution of a display device, and outputs the same signal as a signal  22  to be input to the driver IC and the driving circuit.  
         [0029]    Consequently, when the data enable input signal is input corresponding to an optional resolution in FIG. 1, the values (m, n) of the resolution are automatically recognized to generate a signal to be input to the driver IC and the driving circuit corresponding to the resolution of the display device which is applied at that time. Thus, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions.  
         [0030]    According to the EMBODIMENT 1, the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, the counted value is held and the value held at the last time is utilized for the next horizontal cycle or the next vertical cycle, thereby generating a signal to be input to the driver IC and the driving circuit corresponding to the resolution of the display device which is applied at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions. Thus, it is possible to obtain the effect that a period for development can be shortened and a cost of the development can be reduced.  
         [0031]    According to the Embodiment 1, both horizontal clock counter  12  and vertical clock counter  13  and their associate count memories are provided, however, in case where wither horizontal or vertical counting is needed, provision of either horizontal or vertical counter will ve sufficient.  
       Embodiment 2  
       [0032]    [0032]FIG. 2 is a diagram showing, the structure of a control circuit or a part of the control circuit provided in a display device for each functional block according to an EMBODIMENT 2 of the present invention. In FIG. 2, reference numeral  12  denotes a horizontal clock counter for counting a clock number for a valid data period for each horizontal cycle, that is, a circuit section for counting a resolution in a horizontal direction, reference numeral  13  denotes a vertical clock counter for counting a clock number for a valid data period every vertical cycle, that is, a circuit section for counting a resolution in a vertical direction, reference numeral  14  denotes a horizontal clock count memory for holding a horizontal clock count value counted in a last stage for a predetermined period or all the time, reference numeral  15  denotes a vertical clock count memory for holding a vertical clock count value counted in a last stage for a predetermined period or all the time, reference numeral  16  denotes an input signal generating section for a driver IC and a driving circuit, reference numeral  23  denotes a section for selecting a valid data period in a data enable input signal, reference numeral  17  denotes a horizontal clock count signal, reference numeral  18  denotes a vertical clock count signal, reference numeral  19  denotes a signal indicative of a counter value holding the horizontal clock count signal  17  for a predetermined period or all the time, reference numeral  20  denotes a signal indicative of a counter value holding the vertical clock count signal  18  for a predetermined period or all the time, reference numeral  21  denotes a plurality of signals to be input from the outside, and reference numeral  22  denotes a plurality of signals to be output to the outside (signals to be input to the driver IC and the driving circuit), reference numeral  24  denotes a selecting input signal in a display screen mode for display with an optional display size (resolution), and reference numeral  25  denotes a data enable input signal indicative of a valid data period in the selected resolution. In some cases, the input signal generating section  16  includes a conventional control circuit or a part of the conventional control circuit.  
         [0033]    In the valid data period selecting section  23 , first of all, a display screen mode for display with an optional display size (resolution) is uniquely selected in response to the selecting input signal  24  sent from the outside, and the data enable input signal  25  indicative of the valid data period corresponding to the resolution is generated and output. The structure of the circuit connected following the valid data period selecting section  23  and others and the contents of an operation are the same as those in FIG. 1.  
         [0034]    Consequently, when the display screen mode for display with an optional display size (resolution) is selected in response to the selecting input signal  24  in the display screen mode in FIG. 2, the data enable input signal  25  indicative of the valid data period corresponding to the display screen mode selected at that time is generated by the data valid period selecting section  23  and the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, and the value (count value) of the resolution is automatically recognized to generate the input signal  22  in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions, and the optional display size (resolution) in the display screen mode can be changed easily.  
         [0035]    While the resolution (values of m and n) in the display screen mode can be counted and recognized from the input signal and the display can be carried out corresponding to the display screen mode having an optional resolution in the EMBODIMENT 1, the resolutions of the input signal and the display device should be coincident with each other as necessary conditions. In the EMBODIMENT 2, also in case where the resolutions of the display screen mode and the display device are not coincident with each other, they can become coincident with each other.  
         [0036]    [0036]FIG. 3 is a diagram showing, for each functional block, the structure of a control circuit provided in a display device or a part of the control circuit according to another example of the EMBODIMENT 2 of the present invention. In FIG. 3, reference numeral  16  denotes an input signal generating section in a driver IC and a driving circuit, reference numeral  23  denotes a section for selecting a valid data period in a data enable input signal, reference numeral  21  denotes a plurality of signals to be input from the outside, reference numeral  22  denotes a plurality of signals to be output to the outside, reference numeral  24  denotes a selecting input signal in a display screen mode for display with an optional display size (resolution), and reference numeral  25  denotes a data enable input signal indicative of a valid data period in the selected resolution. In some cases, the input signal generating section  16  includes a conventional control circuit or a part of the control circuit.  
         [0037]    Thus, when the display screen mode for display with an optional display size (resolution) is selected in response to the selecting input signal  24  in the display screen mode in FIG. 3, the data enable input signal  25  indicative of the valid data period corresponding to the display screen mode selected at that time is generated and the input signal generating section  16  simultaneously recognizes, in response to the selecting input signal  24 , the value of the resolution which is obtained at that time, thereby generating the input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions, and the optional display size (resolution) in the display screen mode can be changed easily.  
         [0038]    According to the EMBODIMENT 2, in the function of selecting the display screen mode to be displayed with an optional display size (resolution), the valid data period of the data enable input signal corresponding to the display screen mode selected at that time is controlled, and the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, the counted value is held and the value held at the last time is utilized for the next horizontal cycle or the next vertical cycle, thereby generating a signal to be input to the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain the effect that the optional display size (resolution) in the display screen mode can be changed easily.  
         [0039]    According to the EMBODIMENT 2, in the function of selecting the display screen mode for display with an optional display size (resolution), the valid data period of the data enable input signal corresponding to the display screen mode selected at that time is controlled and the value of the resolution which is obtained at that time is simultaneously recognized in response to the selecting input signal  24 , thereby generating the input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain the effect that an optional display size (resolution) in the display screen mode can be changed easily.  
       Embodiment 3  
       [0040]    [0040]FIG. 4 is a diagram showing, for each functional block, the structure of a control circuit provided in a display device or a part of the control circuit according to an EMBODIMENT 3 of the present invention. In FIG. 4, the reference numeral  12  denotes a horizontal clock counter for counting a clock number for a valid data period every horizontal cycle, that is, a circuit section for counting a resolution in a horizontal direction, reference numeral  13  denotes a vertical clock counter for counting a clock number for a valid data period every vertical cycle, that is, a circuit section for counting a resolution in a vertical direction, reference numeral  14  denotes a horizontal clock count memory for holding a horizontal clock count value counted in a last stage for a predetermined period or all the time, the reference numeral  15  denotes a vertical clock count memory for holding a vertical clock count value counted in a last stage for a predetermined period or all the time, reference numeral  16  denotes an input signal generating section in a driver IC and a driving circuit, reference numeral  26  denotes a section for selecting a valid data period in a display data input signal, reference numeral  17  denotes a horizontal clock count signal, the reference numeral  18  denotes a vertical clock count signal, reference numeral  19  denotes a signal  1  indicative of a counter value holding the horizontal clock count signal  17  for a predetermined period or all the time, reference numeral  20  denotes a signal indicative of a counter value holding the vertical clock count signal  18  for a predetermined period or all the time, reference numeral  21  denotes a plurality of signals to be input from the outside, reference numeral  22  denotes a plurality of signals to be output to the outside, reference numeral  24  denotes a selecting input signal in a display screen mode for display with an optional display size (resolution), and reference numeral  27  denotes a video data input signal having a valid data period in the selected resolution. In some cases, the input signal generating section  16  includes a conventional control circuit or a part of the control circuit.  
         [0041]    In the valid data period selecting section  26 , first of all, a display screen mode for display with an optional display size (resolution) is uniquely selected in response to the selecting input signal  24  sent from the outside, and the video data input signal  27  having the valid data period corresponding to the resolution is generated and output. The structure of the circuit connected following the valid data period selecting section  26  and the contents of operation are the same as those in FIG. 1. The video data input signal  9  included in the input signal  21  sent from the outside which is to be input to the input signal generating section  16  in FIG. 1 is input as the video data input signal  27  in FIG. 4. Moreover, the video data input signal  27  generated in the valid data period selecting section  26  can also be subjected to the masking treatment of an invalid data signal in a portion to be an invalid data period for the video data input signal  9  and can increase or reduce the resolution.  
         [0042]    In the EMBODIMENT 3, also in the case where the resolution of the display screen mode is not coincident with that of the display device, they can become coincident with each other. At this time, the data enable signal  7  may be changed in response to the screen mode selecting input signal  24 , thereby generating a new data enable signal  25  in the same manner as in the EMBODIMENT 2.  
         [0043]    Consequently, when the display screen mode for display with an optional display size (resolution) is selected in response to the selecting input signal  24  in FIG. 4, the video data input signal  27  having the valid data period corresponding to the display screen mode selected at that time is generated and the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, and the value (count value) of the resolution is automatically recognized to generate the input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions, and the optional display size (resolution) in the display screen mode can be changed easily.  
         [0044]    [0044]FIG. 5 is a diagram showing, for each functional block, the structure of a control circuit provided in a display device or a part of the control circuit according to another example of the EMBODIMENT 3 of the present invention. In FIG. 5, reference numeral  16  denotes an input signal generating section in a driver IC and a driving circuit, reference numeral  26  denotes a section for selecting a valid data period in a video data input signal, reference numeral  21  denotes a plurality of signals to be input from the outside, reference numeral  22  denotes a plurality of signals to be output to the outside, reference numeral  24  denotes a selecting input signal in a display screen mode to be displayed with an optional display size (resolution), and reference numeral  27  denotes a video data input signal having a valid data period in the selected resolution. In some cases, the input signal generating section  16  includes a conventional control circuit or a part of the control circuit.  
         [0045]    Thus, when the display screen mode for display with an optional display size (resolution) is selected in response to the selecting input signal  24  in FIG. 5, the video data input signal  27  having the valid data period corresponding to the display screen mode selected at that time is generated and the input signal generating section  16  simultaneously recognizes, in response to the selecting input signal  24 , the value of the resolution which is obtained at that time, thereby generating the input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions, and the optional display size (resolution) in the display screen mode can be changed easily.  
         [0046]    According to the EMBODIMENT 3, in the function of selecting the display screen mode for display with an optional display size (resolution), the valid data period of the video data input signal corresponding to the display screen mode selected at that time is controlled, thereby generating an input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain the effect that an optional display size (resolution) in the display screen mode can be changed easily.  
         [0047]    According to the first and second aspects of the present invention, the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, the counted value is held and the value held at the last time is utilized for the next horizontal cycle or the next vertical cycle, thereby generating a signal to be input to the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, the present invention can be applied to the driver IC and the driving circuit which can be used in the display device having various resolutions. Thus, it is possible to obtain an effect that a period for development can be shortened and a cost of an development can be reduced.  
         [0048]    According to the third and fourth aspects of the present invention, in the function of selecting the display screen mode for display with an optional display size (resolution), the valid data period of the data enable input signal corresponding to the display screen mode selected at that time is controlled, and the valid data period of the data enable input signal is counted with each clock every horizontal cycle and every vertical cycle, the counted value is held and the value held at the last time is utilized for the next horizontal cycle or the next vertical cycle, thereby generating a signal to be input to the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain an effect that the optional display size (resolution) in the display screen mode can be changed easily.  
         [0049]    According to the fifth and sixth aspects of the present invention, in the function of selecting the display screen mode for display with an optional display size (resolution), the valid data period of the data enable input signal corresponding to the display screen mode selected at that time is controlled and the value of the resolution which is obtained at that time is simultaneously recognized in response to the selecting input signal, thereby generating the input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain the effect that the optional display size (resolution) in the display screen mode can be changed easily.  
         [0050]    According to the seventh and eighth aspects of the present invention, in the function of selecting the display screen mode for display with an optional display size (resolution), the valid data period of the video data input signal corresponding to the display screen mode selected at that time is controlled, thereby generating an input signal in the driver IC and the driving circuit corresponding to the resolution of the display device which is obtained at that time. Consequently, it is possible to obtain the effect that the optional display size (resolution) in the display screen mode can be changed easily.  
         [0051]    Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention and all modifications which come within the scope of the appended claims are reserved.