JP2006235283A - Display controller, display control method, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption of a display controller equipped with a volatile memory requesting refreshing operation to maintain storage. <P>SOLUTION: The display controller is equipped with the volatile memory A capable of holding display data used to display an image of one page through refreshing operation, an (N+1)th line memory 32B and an (N)th line memory B33 capable of holding display data as many as display data needed to display one-line images constituting an image of one page, a read control circuit B22 which performs control for reading the display data out of the volatile memory A, and a comparing circuit B34. When display data of one page are read out of the volatile memory A, the comparing circuit B34 uses the (N+1)th line memory B32 and (N)th line memory B33 to decide whether images of all lines constituting the image represented with the display data are identical to one another, and stops the refreshing operation of the volatile memory A when an affirmative decision result is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control technique for supplying display data to a display that displays an image.

In general, the display control apparatus writes display data transferred from the host into an internal buffer, reads out the data from the buffer, and transfers it to the display unit, thereby displaying an image corresponding to the display data in units of pages. The buffer is provided mainly to eliminate inconvenience caused by the difference between the transfer speed from the host side and the transfer speed to the display side, and can store at least one page of display data. Have capacity.

As the number of pixels of the display device increases, the storage capacity required for the buffer also increases.
For this reason, an inexpensive DRAM (Dynamic Random Access Memory) is generally used as a buffer. A DRAM is a volatile memory that requires a refresh operation for storage, and the refresh operation consumes a considerable amount of power. If this power can be reduced, the power consumption of not only the display control device but also the electronic apparatus having the display control device can be greatly reduced.

On the other hand, Patent Document 1 discloses a memory control device in which a refresh operation is temporarily stopped to reduce power consumption. This memory control device stops the refresh operation of the volatile memory from immediately after the power is turned on until the first access, or when there is no access for a predetermined time since the last access. Or only in the storage area being used.
JP-A-7-169267 (Claims)

If the technique disclosed in Patent Document 1 is used, there is a possibility that the power consumption of the display control device can be reduced. However, since the technique disclosed in Patent Document 1 stops a refresh operation of a volatile memory that is not accessed or a part of the volatile memory, a display control device that frequently performs writing and reading over the entire storage area of the buffer. Even if applied to the above, power consumption cannot be significantly reduced.
The present invention has been made in view of such circumstances, and an object of the present invention is to significantly reduce the power consumption of a display control apparatus including a volatile memory that requires a refresh operation for storage.

In order to solve the above-described problem, a display control device according to the present invention has a plurality of pages on a display device that displays an image of one page over the entire screen configured by arranging pixels having a color represented by display data. In a display control apparatus that sequentially supplies display data used for displaying an image over a page unit and displays the image sequentially over a page unit, the display data used for displaying an image over a predetermined number of pages can be retained by a refresh operation. And a first memory capable of holding the same number of display data as the number of display data required to display an image in one area when the image over the predetermined number of pages is divided into a plurality of congruent areas And second
A display unit that reads display data from the volatile memory, and when the display unit reads the display data used to display the image over the predetermined number of pages, the image is divided into the plurality of regions. The display data of one group when the display data is divided into a plurality of groups on the basis of which area is used for displaying an image is held in the first memory and another group A display process of holding the display data in the second memory, and determining whether two images displayed using the display data of both groups are the same by comparing the display data of both groups; Each area when the image over the predetermined number of pages is divided into the plurality of areas based on the result of the comparison process one or more times. Image of the to and comparator means for performing a determination process of determining whether the same to each other, and a stop processing the determination processing result of stopping the refresh operation if affirmative.

According to this display control apparatus, when the display data read from the volatile memory is used to display an image painted in a single color over a predetermined number of pages, the image is congruent with each other. It is determined that the images in each area when divided into the areas are the same, and the refresh operation of the volatile memory is stopped. As a result, display data is lost in the volatile memory, but the display data to be supplied to the display device can be generated using the display data held in the first memory and the second memory of the display control device. No problem. Usually, a volatile memory is required to have a considerable storage capacity, and the refresh operation requires a large amount of power. Therefore, the stop of the refresh operation greatly contributes to the reduction of power consumption.
In addition, when the display data to be supplied to the display is generated using the display data held in the first memory and the second memory, it is not necessary to read the display data from the volatile memory during that time. This also contributes to reduction of power consumption. As mentioned above, according to this display control apparatus, power consumption can be reduced significantly.

In addition, as a comparison method in the comparison process, an arbitrary method capable of obtaining a result necessary for determining whether or not two images displayed using display data of two groups are the same is used. It can be adopted. For example, it is possible to employ a method of comparing display data representing colors of pixels having the same relative position in two images displayed using display data of both groups.
In addition, the comparison unit performs the determination process based on the result of the comparison process one or more times. However, first, the comparison process is performed once, and a result sufficient to perform the determination process is obtained by this one comparison process. If it cannot be obtained, the comparison process may be repeated.

The display data supply form to the display may be a form in which the display data read from the volatile memory by the reading means or a means different from the reading means is supplied to the display as it is. In addition, a form may be provided in which a memory is provided in the display control apparatus and the display is supplied to the display device via the memory. This memory may be the first memory or the second memory, or may be another memory. Alternatively, the display data read from the volatile memory may be subjected to predetermined processing and then supplied to the display.

Further, the mode of reading display data by the reading means, the first memory and the second
The form of holding display data by the memory is arbitrary. For example, the reading means reads the display data from the volatile memory one group at a time without duplication, and in the second and subsequent readings, the one group of display data read this time is stored in the first memory in the previous or first time. The read display data of one group may be held in the second memory,
One group of display data read this time may be stored in a memory (for example, a second memory) different from a memory (for example, a first memory) that stores the one group of display data that was previously read. Further, for example, the reading means reads display data from the volatile memory two groups at a time, holds the display data of one group in the second memory, and stores the display data of the other group in the first memory. In the second and subsequent readings, one group of display data read in the past and one group of display data not read in the past may be read.

The display control device and the aspect described above may be modified as another aspect.
For example, the predetermined number is 1, the area may be a line configured by arranging a plurality of pixels in a predetermined direction in a line, and the screen may be configured by a plurality of lines.
In this aspect, since the comparison is performed in units of lines, not only an image filled with a single color but also an image in which the same image is arranged in units of lines (that is, the color changes in a predetermined direction and is orthogonal to the predetermined direction). In the case of displaying an image whose color does not change in the direction in which the volatile memory is displayed, the refresh operation of the volatile memory is stopped.

Further, for example, the predetermined number may be 1, the area may be a block composed of a plurality of adjacent pixels, and the screen may be composed of a plurality of blocks. In this aspect, since the comparison is performed in units of blocks, not only images that are filled with a single color but also images in which the same images are arranged in units of blocks (for example, the upper half image and the lower half image are the same image). ) Is also displayed, the refresh operation of the volatile memory is stopped.

Further, for example, the predetermined number may be plural, and the area may be a page. In this mode, since the comparison is performed on a page-by-page basis, not only an image filled with a single color,
Even when an image in which the same image is arranged in units of pages (for example, an image of one page displayed first and an image of the same page displayed next) is displayed, the volatile memory is refreshed. Operation stops.

The display control device and various aspects described above may be modified to provide still another aspect.
For example, writing means for writing display data to the volatile memory, monitoring start means for monitoring the behavior of the writing means, and starting the refresh operation when display data is written to the volatile memory by the writing means; You may make it comprise.
Further, for example, external start means may be provided for starting the refresh operation when a start signal instructing the start of the refresh operation is supplied from the outside. According to these aspects, when display data is written into the volatile memory or when a start signal is supplied from the outside, the refresh operation of the volatile memory starts, so that the display data necessary for image display is displayed. Can be supplied to the display without leakage.

The display control device and various aspects described above may be modified to provide still another aspect. For example,
A register that holds at least one bit of data that can be updated from the outside is provided, and the comparison unit performs the comparison process and the determination process only when the data held in the register is predetermined data. It may be. In general, the possibility that images in two areas are the same depends on the nature of the image to be displayed on the display. For example, in the case of a moving image obtained by photographing grass swaying in the wind with a video camera, the possibility that the images in the two regions are the same is extremely low. It is inefficient to perform the comparison process and the determination process for such an image. Therefore, in this aspect, an external device (for example, CPU) can determine whether or not the comparison process and the determination process can be performed. In general, an external device is in a position where it is easier to grasp the nature of an image to be displayed on a display device than a display control device, and thus more appropriately determines whether or not comparison processing and determination processing can be performed. be able to.
As described above, according to this embodiment, the processing efficiency can be improved.

The display control device and various aspects described above can be applied to various electronic devices such as a display device. The applied electronic device has the effects described above compared to the electronic device not applied.

In addition, the display control method according to the present invention is a display used for displaying an image over a plurality of pages on a display that displays an image of one page over the entire screen configured by arranging pixels having a color represented by display data. In a display control method in which data is sequentially supplied in units of pages and the images are sequentially displayed in units of pages, the display data is displayed from a volatile memory that holds display data used for displaying an image over a predetermined number of pages by a refresh operation. And when the display data used to display the image over the predetermined number of pages read by the reading means is divided into a plurality of congruent areas. 1 when the image is divided into a plurality of groups based on which region is used for displaying an image. Whether the display data of one group is held in the first memory and the display data of the other group is held in the second memory, and the two images displayed using the display data of both groups are the same Based on the comparison process for determining whether or not the display data of both groups are compared and the determination result of the comparison process one or more times, display is performed using the display data read by the reading means. Determining whether the images in each region when the image over the predetermined number of pages is divided into the plurality of regions are the same, and stopping the refresh operation when it is determined that they are the same Process.
According to this display control method, the same effect as that obtained by the display control device can be obtained.

FIG. 1 is a block diagram illustrating a configuration of a display device 1 including a display control device 10 according to an embodiment of the present invention. The display device 1 includes a host 2 having a CPU (Central Processing Unit).
The display data and the host control signal are supplied to display an image represented by the display data, and the operation follows the host control signal. As a form of supplying display data and a host control signal from the host 2 to the display device 1, any known form can be adopted.

The display device 1 includes a display panel 20 and a display control device 10 that receives display data and host control signals supplied from the host 2 and supplies display data and display control signals to the display panel 20.
The display panel 20 displays an image represented by the display data supplied from the display control device 10 on the screen R, and is arranged in a matrix in the screen R over the X and Y directions orthogonal to each other. A plurality of pixels P and a scanning line driving circuit 2 for driving each pixel P
1 and a data line driving circuit 22. The scanning line driving circuit 21 sequentially selects the pixels P of each line arranged in the X direction for each horizontal scanning period. On the other hand, the data line driving circuit 22 outputs an image signal corresponding to the gradation (color) specified by the display data to each of the pixels P for one line selected by the scanning line driving circuit 21. Each pixel P has an electro-optical element that emits light with luminance (color) corresponding to the level of the image signal. The electro-optical element is an OLED element such as an organic EL (ElectroLuminescence).

The display control signal supplied from the display control device 10 to the display panel 20 includes a synchronization signal and a clock signal. As the synchronization signal, a horizontal synchronization signal having a period corresponding to the horizontal scanning period in which the pixels P of each line are selected and an image signal are supplied to all the pixels P of the display panel 20 (that is, all lines). Vertical synchronization signals having a period corresponding to the vertical scanning period (which is selected by the scanning line driving circuit 21). As the clock signal, there is a dot clock signal having a period corresponding to a time length obtained by dividing one horizontal scanning period according to the number of pixels of each line.

The display control device 10 includes a volatile memory A and a display control circuit B, and sequentially supplies a plurality of units of display data, with the same number of display data as the number of pixels P constituting the screen R as one unit.
When an image over the entire screen R of the display panel 20 is an image of one page, the image over a plurality of pages is sequentially displayed in units of pages on the display panel 20 to which display data of a plurality of units is sequentially supplied. Of course, a plurality of units of display data are sequentially supplied from the host 2 to the display control device 10 as well.

At least one of the transfer speed and transfer timing of display data differs between the host 2 and the display control device 10 and between the display control device 10 and the display panel 20. For this reason,
The display control device 10 needs a buffer for eliminating the inconvenience due to this difference. The volatile memory A is used as this buffer. The volatile memory A is a DRAM having a storage area capable of holding display data for one page. The DRAM is used to reduce the manufacturing cost.

Here, the design concept of the display control apparatus 10 will be described.
A DRAM is a semiconductor memory that requires a refresh operation for storage, and the refresh operation of the volatile memory A consumes a considerable amount of power. In order to reduce this power, there is a one-page image that can be reproduced by repeatedly arranging the partial images, and when such an image is displayed, there is a high possibility that the same image will be displayed next. Focusing on
The display control apparatus 10 temporarily stops the refresh operation of the volatile memory A and the read operation from the volatile memory A when such an image is displayed. Since the display control device 10 is based on such a design concept, a semiconductor memory other than a DRAM that requires a refresh operation to hold a memory may be used as a buffer.

FIG. 2 is a block diagram showing the configuration of the display control circuit B. As shown in the figure, the display control circuit B includes a host I / F (interface) circuit B1, a memory control circuit B2, and a display I / F.
A circuit B3 is included.
The host I / F circuit B1 controls the I / F between the host 2 and includes a host I / F control circuit B11 and a FIFO (First In First Out) buffer B12. Host I /
When the supply of display data from the host 2 is started, the F control circuit B11 controls each part of the host I / F circuit B1 so that the display data from the host 2 is taken into the buffer B12. A write start signal for starting control and a refresh start signal for starting refresh control described later are supplied to the memory control circuit B2. Buffer B
Reference numeral 12 temporarily holds display data, and its storage capacity is extremely smaller than that of the volatile memory A. As the buffer B12, any rewritable semiconductor memory can be used. However, from the viewpoint of reducing power consumption, it is desirable to use a memory that does not require a refresh operation for storage.

The memory control circuit B2 controls the volatile memory A, and the write control circuit B21,
It has a read control circuit B22 and a refresh control circuit B23.
The write control circuit B21 starts write control when a write start signal is supplied from the host I / F circuit B1. The write control is a control for repeatedly performing a write operation of extracting display data from the buffer B12 and writing it to the volatile memory A until the supply of display data from the host 2 is stopped. In the write control, a memory control signal for instructing a write operation and an address designation signal for designating a write address are repeatedly supplied from the memory control circuit B2 to the volatile memory A.

The read control circuit B22 starts read control when the display data held in the volatile memory A reaches one page, and reads when the display data held in the volatile memory A is less than one page. Stop control. The read control is a control for repeatedly performing a read operation of reading display data from the volatile memory A and supplying it to the display I / F circuit B3. In the read control, a memory control signal for instructing a read operation and an address designation signal for designating a read address are repeatedly supplied from the memory control circuit B2 to the volatile memory A.

The refresh control circuit B23 starts refresh control when a refresh start signal is supplied from the host I / F circuit B1. The refresh control is control for causing the volatile memory A to repeatedly perform a refresh operation. In refresh control, the memory control circuit B
A refresh command (memory control signal) that triggers a refresh operation is supplied from 2 to the volatile memory A at a predetermined timing. The refresh control circuit B23 stops the refresh control when a refresh stop signal described later is supplied from the display I / F circuit B3.

The display I / F circuit B3 controls the I / F between the display panel 20 and the display I / F control circuit B31, the (N + 1) th line memory B32, the Nth line memory B33, and the comparison circuit B.
34.
Each of the Nth line memory B33 and the (N + 1) th line memory B32 is a memory that holds display data in units of one line, and holds display data read from the volatile memory A by a read operation. These memories B33 and B32 may be any rewritable semiconductor memory. However, from the viewpoint of reducing power consumption, it is desirable that a refresh operation is not required for storage.

In the following description, “first line data”, “second line data”, “third” are set according to the order in which the display data for one line constituting the display data for one page is supplied to the display panel 20. Line data ", ... When one page is composed of M lines, the display data held in the Nth line memory B33 in the read operation for the display data for one page is the display data for the first line and the display for the second line. The display data updated in the order of the data, the display data for the third line,..., The display data for the (M−1) th line, and the display data held in the (N + 1) th line memory B32 are the display data for the second line, the third The display data for the line, the display data for the fourth line,..., And the Mth line data are updated in this order.
In addition, the update timing of both is synchronized with each other. When the display data held in the Nth line memory B33 is the Nth line data, the display data held in the (N + 1) th line memory B32 is the N + 1th line. It becomes data. Therefore, hereinafter, the display data held in the Nth line memory B33 is referred to as “Nth line data”, and the display data held in the N + 1th line memory B32 is referred to as “N + 1th line data”.

The method for realizing the above update is arbitrary. For example, display data for one line is read out by one read operation, and the (N + 1) -th display data is read out for one line.
It is also possible to update the line data, save the (N + 1) th line data prior to this update, and update the Nth line data with the saved (N + 1) th line data. Further, for example, display data for two lines is read by one read operation, and this read operation is repeated M−1 times. In each read operation, the display data for the previous one line is replaced with the Nth display data.
For the line data, the (N + 1) th line data may be updated with the display data for the subsequent one line.

The display I / F control circuit B31 supplies display data to the data line driving circuit 22 of the display panel 20 in units of one line for each horizontal scanning period according to the horizontal synchronization signal and correctly displays an image using the display data. A display control signal is supplied to the scanning line driving circuit 21.
The display data is supplied to the display panel 20 in a form read from the Nth line memory B33, read from the N + 1th line memory B32, or volatile. A configuration may be adopted in which data read from the memory A is supplied as it is.

The comparison circuit B34 updates the Nth line data and the (N + 1) th line data as described above, while the display data for one page is supplied to the display panel 20 (the display data for one page is stored in the volatile memory A). When the image of each page is divided into a plurality of lines when the image of one page is divided into a plurality of lines, and the result of this determination process is affirmative Only, a refresh stop signal for stopping the refresh control is supplied to the memory control circuit B2. In this case, the comparison circuit B34 controls each part of the display I / F circuit B3 so that the Nth line data or the N + 1th line data is repeatedly supplied to the display panel 20 until the next read operation is started. .

Further, the comparison circuit B34 performs a comparison process for comparing the Nth line data and the N + 1th line data to obtain a comparison result for the above determination process. This comparison result indicates whether or not the image displayed by supplying the Nth line data to the display panel 20 and the image displayed by supplying the N + 1th line data to the display panel 20 are the same. . That is, the comparison circuit B34
Performs the determination process based on the comparison result obtained by the comparison process. As a comparison method that brings about the above comparison result, there is a method of comparing display data representing colors of pixels having the same relative position in the image related to the Nth line data and the image related to the (N + 1) th line data.

FIG. 3 is a flowchart showing a process performed by the comparison circuit B 34 constituting the display control circuit B regarding the stop of the refresh operation. As shown in the figure, the comparison circuit B34 first updates the Nth line data with the first line data read from the volatile memory A by the read operation, while being read from the volatile memory A by the read operation. N + 1th line data
The line data is updated (step Sa1). Next, the Nth line data and the (N + 1) th line data are compared, and it is determined whether or not the two images relating to both are the same (step Sa2).
). If it is determined that they are not the same, the refresh operation of the volatile memory A is continued (step Sa3). Specifically, a signal to continue the refresh operation is supplied to the memory control circuit B2, or nothing is done.

On the other hand, if it is determined that they are the same, it is determined whether or not the above determination has been completed for all display data for one page, that is, whether or not the page has been completed (step Sa4).
. If it is determined that the page has not ended, the Nth line data is updated with the second line data read from the volatile memory A by the read operation, while the Nth line data is read by the read operation. The N + 1th line data is updated with the third line data (step Sa1).

Thereafter, the same processing as described above is repeated for subsequent line data until it is determined that the image related to the Nth line data and the image related to the (N + 1) th line data are not the same, or until it is determined that the page is completed. If it is determined in step Sa4 that the page is completed, that is, if it is determined that the images related to all the line data constituting the display data for one page are the same, the comparison circuit B34 stops refreshing. Signal is sent to memory control circuit B
2 to stop the refresh operation of the volatile memory A (step Sa
5).

FIG. 4 is a timing chart showing an operation example of the display control apparatus 10. Hereinafter, the operation of the display apparatus 1 will be described mainly with reference to this figure. In this operation example, it is assumed that the transfer rate on the display panel 20 side is faster than the transfer rate on the host 2 side. Volatile memory A
It is assumed that display data for one page is already held in. Further, the image represented by the display data is an image in which one area divided by one diagonal line is filled with white and the other area is filled with black (hereinafter referred to as “first image”). Suppose that

In the figure, a host control signal for starting the supply of display data from the host 2 has already been supplied, and an image of one page (hereinafter referred to as a “second image”) that is filled with a single color from the host 2.
The supply of display data for one page representing is started. Therefore, the host I /
A write start signal is supplied from the F control circuit B11 to the memory control circuit B2, the write control circuit B21 of the memory control circuit B2 performs write control, and the display data supplied from the host 2 passes through the buffer B12. Writing to the volatile memory A continues. On the other hand, the refresh control circuit B23 starts refresh control, and the volatile memory A performs a refresh operation at a predetermined cycle. For this reason, the display data written in the volatile memory A is retained.

The read control circuit B22 has already started read control, and the display data held in the volatile memory A is read and supplied to the display panel 20 via the display I / F circuit B3. As shown in the figure, the display data related to the first image is read out during the write control of the display data related to the second image, and the first image is displayed on the display panel 20. On the other hand, in the display I / F circuit B3, the processing shown in FIG. 3 is performed on the display data for one page read from the volatile memory A. However, since this display data relates to the first image, the determination result in step Sa2 is “No”. Therefore, the refresh operation of the volatile memory A is continued.

As soon as the above reading is completed, the next reading (hatched portion in the figure) is started. As shown in the figure, since this reading is completed after the write control of the display data related to the second image is stopped, the second image is displayed on the display panel 20. On the other hand, display I / F
In the circuit B3, the display data for one page read from the volatile memory A is displayed as shown in FIG.
The process shown in FIG. Since this display data relates to the second image, step S
The determination result of a2 continues to be “Yes”, and finally the determination result of step Sa4 is “Yes.
s ". Therefore, the comparison circuit B34 supplies a refresh stop signal to the memory control circuit B2.

Thereby, the refresh control circuit B23 stops the refresh control, and the read control circuit B22 stops the read control. Thereafter, the refresh operation of the volatile memory A and the read operation from the volatile memory A are stopped. As a result, the display data held in the volatile memory A is eventually lost, but thereafter, the display I / F circuit B3 to the display panel 20 has the Nth
Since the line data or the (N + 1) th line data is repeatedly supplied, the second image is continuously displayed on the display panel 20.

Next, when a host control signal for starting supply of display data is supplied from the host 2 and supply of display data for one page relating to the first image is started from the host 2, the host I / F is started.
A write start signal and a refresh start signal are supplied from the control circuit B11 to the memory control circuit B2. As a result, the write control circuit B21 starts write control, and the refresh control circuit B23 starts refresh control. As a result, the write operation to the volatile memory A and the refresh operation of the volatile memory A are started. When the display data for one page is written in the volatile memory A and the write control is stopped, the read control circuit B22 starts the read control.

As described above, according to the display control device 10, display data for one page representing an image of one page in which the images of the respective lines are the same when divided into a plurality of lines is stored from the volatile memory A. When read, the refresh operation of the volatile memory A is stopped until the next display data is written to the volatile memory A (see FIG. 4). Thereafter, the display data supplied to the display panel 20 is reproduced from the display data held in the Nth line memory B33 or the N + 1th line memory B32. Therefore, according to the display control device 10, it is possible to significantly reduce power consumption as compared with a device that constantly refreshes a volatile memory used as a buffer for adjusting a transfer rate.

In the operation example of FIG. 4, the transfer rate on the display panel 20 side is faster than the transfer rate on the host 2 side, and one display data is read from the volatile memory A a plurality of times. Of these multiple readings, the second and subsequent readings are not required by the above control. That is, according to the display control device 10, the read operation can be reduced. this is,
This leads to further lower power consumption.
These contribute to the reduction of power consumption of the electronic device including the display control device 10.

Further, according to the display control device 10, since the refresh operation is resumed when display data is supplied from the host 2, a situation in which display data to be processed that is concerned due to stopping the refresh operation is leaked. Can be avoided.

In addition, according to the display control apparatus 10, the Nth line data changes in the order of the first line data, the second line data, the third line data,. A configuration in which the Nth line data (or N + 1th line data) is supplied to the display panel 20 consistently even when not stopped can be adopted.

Further, the display control device 10 can be modified as follows.
For example, display data may be compared not in line units but in arbitrary block units that can equally divide an image of one page. Of course, a plurality of lines may be one block. For example, instead of the volatile memory A, a volatile memory that can hold display data for a plurality of pages may be used, and display data may be compared in units of pages. That is, display data may be compared in units of areas when an image covering one or more pages is divided into a plurality of congruent areas.

Further, for example, the host I / F control circuit B11 may be modified to output a refresh start signal when a predetermined start signal instructing the start of refresh is supplied from the host side.
Further, for example, the display control device 10 is provided with a register that holds at least one bit of data that can be updated from the outside, and the display control circuit B operates according to the data held in the register. The operation mode may be changed from the host side. As operation modes in this case, there are a mode for performing the processing shown in FIG. 4 and a mode for not performing the processing. In this embodiment, by performing appropriate control on the host side, the situation shown in FIG. 4 can be avoided when it is clear that it is not necessary. Therefore, improvement in processing efficiency of the display control apparatus 10 is expected.

In addition, the display control device 10 or the display control circuit B and the display panel 20 may be integrated, or the display control device 10 or the display control circuit B and the scanning line driving circuit 21 may be integrated. The display control device 10 or the display control circuit B and the data line driving circuit 2
2 may be integrated. The display control device 10 or the display control circuit B
It can be realized by hardware such as a DSP (Digital Signal Processor) dedicated to image data processing, or can be realized by cooperation of a computer such as a CPU and a program. This program is, for example, a content that causes the computer to execute the processing shown in FIG.

Moreover, although the display panel 20 in which the pixels P including the OLED elements are arranged is illustrated, each pixel P
The configuration of the display panel 20 is arbitrarily changed. For example, the present invention is also applied to a display device including various display panels such as a liquid crystal display panel, a field emission display (FED) panel, and a plasma display panel. Therefore, the pixel in the present invention is sufficient if it is an element serving as a unit for displaying the gradation designated by the image data, and its specific configuration is not limited. Typically, an element including an electro-optical element having a property in which optical characteristics such as transmittance and luminance are changed by applying electric energy is employed as a pixel.

The display device 1 and the device obtained by modifying the display device 1 can be applied to any electronic device that displays an image. Examples of such electronic devices are listed below.
FIG. 5 shows a configuration of a mobile personal computer to which the display device 1 is applied. The personal computer 2000 includes the display device 1 and a main body 2010. Main unit 20
10, a power switch 2001 and a keyboard 2002 are provided.
FIG. 6 shows a configuration of a mobile phone to which the display device 1 is applied. The mobile phone 3000 includes the display device 1 in addition to the plurality of operation buttons 3001 and the scroll buttons 3002. By operating the scroll button 3002, the screen displayed on the display device 1 is scrolled.
FIG. 7 shows a portable information terminal (PDA: Personal Digital Assistants) to which the display device 1 is applied.
). The information portable terminal 4000 includes the display device 1 in addition to the plurality of operation buttons 4001 and the power switch 4002. When a plurality of operation buttons 4001 are operated, various kinds of information such as an address book and a schedule book are displayed on the display device 1.
The electronic apparatus to which the display device according to the present invention is applied includes, in addition to those shown in FIGS. 5 to 7, a digital still camera, a liquid crystal television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device , Pagers, electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, devices equipped with touch panels, and the like.

It is a block diagram which shows the structure of the display apparatus 1 provided with the display control apparatus 10 which concerns on one Embodiment of this invention. 3 is a block diagram showing a configuration of a display control circuit B that constitutes the display control device 10. FIG. It is a flowchart which shows the process which the comparison circuit B34 which comprises the display control circuit B performs regarding a stop of refresh operation. 3 is a timing chart illustrating an operation example of the display control apparatus 10. 1 is a perspective view illustrating a configuration of a personal computer to which a display device 1 is applied. 1 is a perspective view illustrating a configuration of a mobile phone to which a display device 1 is applied. It is a perspective view which shows the structure of the portable information terminal to which the display apparatus 1 is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... Host, 10 ... Display control apparatus, 20 ... Display panel, 21 ... Scan line drive circuit, 22 ... Data line drive circuit, A ... Volatile memory, B ... Display control circuit, B1 ... Host I / F circuit, B11 ... host I / F control circuit, B12 ... buffer, B2 ... memory control circuit, B21 ... write control circuit, B22 ... read control circuit, B23 ... refresh control circuit,
B3: Display I / F circuit, B31: Display I / F control circuit, B32: N + 1-th line memory,
B33 ... N-th line memory, B34 ... comparison circuit, P ... pixel, R ... screen.

Claims (9)

Display data used to display an image over a plurality of pages is sequentially supplied to a display that displays an image of one page over the entire screen configured by arranging pixels having colors represented by display data. In the display control device that sequentially displays the page unit,
A volatile memory capable of holding display data used for displaying an image over a predetermined number of pages by a refresh operation;
A first memory and a second memory capable of holding the same number of display data as the number of display data required to display an image in one area when the image over the predetermined number of pages is divided into a plurality of congruent areas; Memory,
Reading means for reading display data from the volatile memory;
When display data to be used for displaying an image over the predetermined number of pages is read by the reading means, based on which area is used to display an image when the image is divided into the plurality of areas. When the display data is divided into a plurality of groups, the display data of one group is held in the first memory and the display data of the other group is held in the second memory. 2 displayed using data
A comparison process for determining whether two images are the same by comparing the display data of both groups and an image over the predetermined number of pages based on a result of the comparison process one or more times. A comparison between a determination process for determining whether images in each area when divided into areas are the same as each other and a stop process for stopping the refresh operation if the result of the determination process is positive And a display control device. The predetermined number is one;
The region is a line composed of a plurality of pixels arranged in a line in a predetermined direction,
The display control apparatus according to claim 1, wherein the screen includes a plurality of lines. The predetermined number is one;
The region is a block composed of a plurality of adjacent pixels,
The display control apparatus according to claim 1, wherein the screen includes a plurality of blocks. The predetermined number is plural,
The display control apparatus according to claim 1, wherein the region is a page. Writing means for writing display data to the volatile memory;
5. A monitoring start unit that monitors the behavior of the writing unit and starts the refresh operation when display data is written to the volatile memory by the writing unit. A display control device according to claim 1. 5. The display control apparatus according to claim 1, further comprising an external start unit that starts the refresh operation when a start signal instructing the start of the refresh operation is supplied from the outside. A register for holding at least one bit of data that can be updated externally;
The comparison means only when the data held in the register is predetermined data,
The display control apparatus according to claim 1, wherein the comparison process and the determination are performed.   An electronic apparatus comprising the display control device according to claim 1. Display data used to display an image over a plurality of pages is sequentially supplied to a display that displays an image of one page over the entire screen configured by arranging pixels having colors represented by display data. In the display control method for displaying the images sequentially in page units,
A reading process of reading the display data from the volatile memory holding the display data used for displaying an image over a predetermined number of pages by a refresh operation;
When the display data used for displaying the image over the predetermined number of pages, which is started after the start of the reading process and read by the reading means, is divided into a plurality of congruent regions, the image in any region The display data of one group when it is divided into a plurality of groups based on whether it is used for display of the first group is held in the first memory, the display data of the other group is held in the second memory, A comparison process for determining whether two images displayed using the display data of both groups are the same by comparing the display data of both groups;
Each area when the image over the predetermined number of pages displayed using the display data read by the reading means is divided into the plurality of areas based on the determination result of the comparison process one or more times A display control method comprising: determining whether or not the images in the image are identical to each other, and stopping the refresh operation when the images are determined to be identical.

Images