Patent Publication Number: US-2010128044-A1

Title: Data processing circuit and display using the same

Description:
This application claims the benefit of Taiwan application Serial No. 97145377, filed Nov. 24, 2008, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to a data processing circuit, and more particularly, to a data processing circuit for eliminating a tearing effect of a display. 
     2. Description of the Related Art 
     In current technology, a display system normally includes a main control circuit, a display driver and a display panel. For example, the display panel can be a liquid crystal display panel. The display driver includes a frame buffer for buffering the image data provided by the main control circuit. The display driver is further for providing the image data buffered in the frame buffer to the liquid crystal display panel to display the corresponding frame. 
     Generally speaking, the operation of the main control circuit providing the image data to the frame buffer should be synchronous with the operation of the frame buffer providing the image data to the liquid crystal display panel to avoid a tearing effect of the image displayed on the liquid crystal display panel. Therefore, how to effectively synchronize the input and output operations of the frame buffer has become an essential goal of the relevant industrial&#39;s endeavor. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a data processing circuit. The data processing circuit includes a main control circuit obtaining scan information of the frame buffer by reading a register installed in a driver integrated circuit (IC) of the display and accordingly synchronizing the writing and reading operations of the frame buffer. 
     According to a first aspect of the present invention, a data processing circuit is provided. The data processing circuit is for driving a display panel to display an image frame, and the display panel comprises N*M pixels, wherein N, M are natural numbers larger than 1. The data processing circuit comprises a main control circuit and a display driver. The main control circuit comprises a processor for providing N*M pieces of image data. The display driver comprises a display controller, a frame buffer and a scan register. The display controller is for receiving and providing the N*M pieces of image data. The frame buffer is for buffering the N*M pieces of image data provided by the display controller and outputting the N*M pieces of image data in a transmission period to drive the corresponding pixels of the display panel. The scan register is for recording scan information, wherein the scan information indicates the image data being currently outputted by the frame buffer. The processor is further used for reading the scan register to obtain the scan information and adjusting transmission of the image data according to the scan information. 
     According to a second aspect of the present invention, a display is provided. The display comprises a display panel with N*M pixels, a main control circuit and a display driver, wherein N, M are natural numbers larger than 1. The main control circuit comprises a processor for providing N*M pieces of image data. The display driver comprises a display controller, a frame buffer and a scan register. The display controller is for receiving and providing the N*M pieces of image data. The frame buffer is for buffering the N*M pieces of image data provided by the display controller and outputting the N*M pieces of image data in a transmission period to drive the corresponding pixels of the display panel. The scan register is for recording scan information, wherein the scan information indicates the image data currently outputted by the frame buffer. The processor is further used for reading the scan register to obtain the scan information and adjusting transmission of the image data according to the scan information. 
     The invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a display according to a preferred embodiment of the invention. 
         FIG. 2  is a signal timing diagram of the display in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a block diagram of a display according to a preferred embodiment of the invention is shown. The display  1  includes a data processing circuit  10  and a display panel  100 . The data processing circuit  10  includes a main control circuit  12  and a display driver  14 . For example, the display panel  100  is a liquid crystal display panel, which includes a pixel array having N*M pixels, wherein N, M are natural numbers larger than 1. 
     The main control circuit  12  includes a processor  12   a  and a data bus controller  12   b . The main control circuit  12  provides N*M pieces of image data Da 1 , Da 2 , . . . , DaN, . . . , DaN*M to the display driver  14 . In the embodiment, the N*M pieces of image are respectively corresponding to the first row of pixels to the N th  row of pixels in the display panel  100  for displaying a complete frame, and it is supposed a non-display time between two frames is a period of time for displaying L rows of pixels, wherein L is an integer larger than or equal to zero. 
     The display driver  14  includes a data bus controller  14   a , a display controller  14   b , a scan register  14   c  and a frame buffer  14   d . The display controller  14   b  is for receiving and storing the N*M pieces of image data Da 1 ˜DaN*M provided by the main control circuit  12  into the frame buffer  14   d  and outputting the image data in the next frame period to drive the corresponding pixels of the liquid crystal panel. 
     The scan register  14   c  is coupled to the frame buffer  14   d  for buffering a scan information Sin. The scan information Sin indicates which row of pixels in the display panel  100  is currently being scanned by the frame buffer  14   d.    
     The processor  12   a  is for reading the scan register  14   c  and determining the time for outputting the next N*M pieces of image data according to the scan information Sin such that the operation of inputting the pixel data to the frame buffer  14   d  and the operation of outputting the pixel data from the frame buffer  14   d  to the display panel  100  can be synchronized. 
     For example, referring to  FIG. 2 , a signal timing diagram of the display  1  in  FIG. 1  is shown. In  FIG. 2 , a complete frame period, symbolized as TPF, includes a period of display time TPC and a period of non-display time TPF-TPC. The display time TPC includes a scan time for scanning N rows of pixels, and the non-display time is supposed to be a scan time for scanning L rows of pixels. 
     The processor  12   a  reads the scan register  14   c  to obtain the pixel data of the i th  row of pixels in the display panel  100 , which is currently outputted by the frame buffer  14   d . Therefore, the processor  12   a  can easily obtain the following estimation according to the value i and the row numbers N and L: 
     I. The next frame period of the display driver will start after a time period for scanning (N-i) rows of pixels. 
     II. The first row of pixels in the next frame period of the display driver will start to be scanned after a time period for scanning (L+N−i) rows of pixels. 
     The main control circuit  12  can determine the transmission period of the next frame (the next N*M pieces of image data) according to the above estimation and the timing of the main control circuit  12 . Therefore, the N*M pieces of image data can be outputted at the correct time point to synchronize the input and output operations of the frame buffer  14   d , thereby avoiding occurrence of the tearing effect. 
     However, the invention is not limited to the above operation. For example, after the processor  12   a  obtains the current scan condition of the display panel  100  according to the scan information, the output condition (output timing) of the processor  12   a  as outputting the image data can also be adjusted timely to synchronize the input and output operations of the frame buffer  14   d . All the alternatives are not apart from the scope of the invention. 
     Besides, in the embodiment of  FIG. 1 , the main control circuit  12  and the display driver  14  further include data bus controllers  12   b  and  14   a , respectively. The processor  12   a  of the main control circuit  12  can effectively provide the pixel data Da 1 ˜DaN to the display controller  14   b  and the frame buffer  14   d  of the display driver  14  through a bus between the data bus controllers  12   b  and  14   a.    
     As mentioned above, in the embodiment, the main control circuit  12  reads the scan information stored in the scan register  14   c  to obtain the current scan position of the display panel  100  and accordingly control the timing of providing the pixel data to the frame buffer such that the writing and reading operations of the frame buffer can be synchronized. Therefore, the data processing circuit  10  can synchronize the writing and reading operations of the frame buffer to avoid the above-mentioned tearing effect. 
     Further, in the embodiment, owing that the data processing circuit  10  just needs an extra register (the scan register  14   c ) for storing the scan information, the data processing circuit  10  can directly apply the currently-existing structure of data processing and main control circuits to synchronize the writing and reading operations of the frame buffer without needing too much modification of the hardware structure. Therefore, the data processing circuit of the invention not only prevents the prior-art tearing effect, but also reduces the cost in circuit design. 
     While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.