Control circuit, screen driving circuit, chip and screen for screen display

Abstract

The application provides a control circuit, a screen driving circuit, a chip and a screen for screen display. The frame display enabling signal is changed by changing the total frame number in a unit time and the display frame number in a unit time, so as to change the time of the liquid crystal screen display pattern in a unit time to realize the gray scale adjustment. According to the visual persistence principle, the display effects such as gradual brightening, gradual dimming, breathing and the like can be realized, the gray scale control is no longer limited to the electrical specifications of the liquid crystal screen, the software control complexity is greatly reduced, and a good visual perception is obtained.

Description

Technical Field

[0001] This application relates to the field of liquid crystal screen backlight driving technology, specifically to control circuits, screen driving circuits, chips, and screens used for screen display. Background Technology

[0002] Liquid crystal displays (LCDs) are widely used in display instruments due to their excellent characteristics such as low operating voltage, long lifespan, low power consumption, easy integration, low electromagnetic radiation, and large display information capacity. However, due to the unique imaging principle of LCD screens, their display effect is relatively limited and cannot meet the application needs of the market. Existing solutions for adjusting LCD grayscale are achieved by adjusting the driving voltage, but the grayscale levels are limited by the electrical characteristics of the screen and cannot select local pixels for grayscale control. Furthermore, existing software solutions are only applicable to screens with a 1 / 2 BIAS resolution, and the control program is relatively complex and lacks versatility. Summary of the Invention

[0003] This application provides a control circuit, a screen driver circuit, a chip, and a screen for screen display, with the specific technical solutions as follows:

[0004] A control circuit for screen display includes a first counter, a second counter, a comparator, a first data selector, a second data selector, a first AND gate, a second AND gate, and an SEG terminal level selection signal generator. The first input of the comparator is connected to the first counter to receive the total frame count value per unit time output by the first counter. The second input of the comparator is connected to the second counter to receive the display frame count value per unit time output by the second counter. The comparator compares the total frame count value per unit time with the display frame count value per unit time, and then transmits the comparison result to the address selection terminal of the first data selector through the output of the comparator. The first data selector selects a corresponding preset signal as a frame display enable signal based on the comparison result output by the comparator and transmits it to the first AND gate. The frame display enable signal is used to indicate... The first AND gate indicates whether an image needs to be displayed in the current frame; the first AND gate receives the frame display enable signal output by the first data selector and the externally input LCD screen display data and performs an AND operation, then transmits the AND operation result to the first input terminal of the second data selector; the second AND gate receives the COM terminal breathing enable and the SEG terminal breathing enable and performs an AND operation, then transmits the AND operation result to the address selection terminal of the second data selector; the second input terminal of the second data selector is used to receive the externally input LCD screen display data, and the second data selector selects the LCD screen display data or the AND operation result of the first AND gate as the input of the SEG terminal level selection signal generator according to the AND operation result of the second AND gate; the SEG terminal level selection signal generator is used to generate a corresponding SEG terminal level selection signal according to the LCD screen display data or the AND operation result of the first AND gate, and the SEG terminal level selection signal is used to control the grayscale of the LCD screen.

[0005] Furthermore, the control circuit for screen display also includes a first register and a second register, wherein the first register is connected to the first input terminal of the second AND gate and is used to transmit the COM terminal breathing enable to the second AND gate, and the second register is connected to the second input terminal of the second AND gate and is used to transmit the SEG terminal breathing enable to the second AND gate.

[0006] A screen driving circuit includes a control circuit for screen display, and further includes a data reading module, a register configuration module, and a drive control signal generation module. The data reading module and the register configuration module are respectively connected to the drive control signal generation module. The data reading module reads LCD screen display data stored in external video memory and transmits it to the drive control signal generation module. The register configuration module configures the functional parameters of the drive control signal generation module. The drive control signal generation module generates a COM terminal level selection signal and a SEG terminal level selection signal based on the LCD screen display data. The drive control signal generation module includes the control circuit for screen display, and the SEG terminal level selection signal controls the grayscale of the LCD screen.

[0007] Furthermore, the data reading module is connected to a first AND gate and a second data selector, and is used to read the LCD screen display data stored in the external video memory and transmit it to the first AND gate and the second data selector. The control circuit for screen display includes the first AND gate and the second data selector.

[0008] Furthermore, the register configuration module is connected to the first counter, the second counter, the first register, and the second register, and is used to configure the functional parameters of the control circuit for screen display, wherein the control circuit for screen display includes the first counter, the second counter, the first register, and the second register.

[0009] Furthermore, the screen driving circuit includes a video memory control module, which is connected to the data reading module. The video memory control module communicates with the outside via an address bus and a data bus to control the external central processing unit to read and write to the external video memory, so that the data reading module can read the LCD screen display data stored in the external video memory.

[0010] Furthermore, the screen driving circuit includes a signal synchronization module, which is connected to the register configuration module and the drive control signal generation module, and is used to perform cross-time domain synchronization between the system clock and the operating clock of the screen driving circuit.

[0011] Furthermore, the screen driving circuit includes an analog voltage generation module, which is connected to the drive control signal generation module and is used to output an analog voltage to drive the LCD screen according to the COM terminal level selection signal and the SEG terminal level selection signal.

[0012] A chip, the chip including the screen driving circuit.

[0013] A screen, the screen including the chip.

[0014] The control circuit for screen display described in this application can change the frame display enable signal by changing the total number of frames per unit time and the number of displayed frames per unit time, thereby changing the time for the LCD screen to display the pattern per unit time to achieve grayscale adjustment. Utilizing the principle of visual persistence, display effects such as gradual brightening, gradual dimming, and breathing can be achieved, so that grayscale control is no longer limited by the electrical specifications of the LCD screen, greatly reducing the complexity of software control and providing a good visual experience. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a control circuit for screen display according to one embodiment of this application.

[0016] Figure 2 This is a schematic diagram of a screen driving circuit according to one embodiment of this application.

[0017] Figure 3 This is a schematic diagram illustrating the basic principle of grayscale control of a liquid crystal screen according to one embodiment of this application.

[0018] Figure 4 This is a schematic diagram of the breathing enable activation timing diagram according to one embodiment of this application.

[0019] Figure 5 This is a schematic diagram of the breathing enable shutdown timing diagram according to one embodiment of this application. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described below are only for explaining this application and are not intended to limit this application.

[0021] In the following description, specific details are set forth to provide a thorough understanding of the embodiments. However, those skilled in the art will understand that the embodiments may be practiced without these specific details. For example, circuits may be shown in block diagrams so as not to obscure the embodiments with unnecessary detail. In other instances, well-known circuits, structures, and techniques may not be shown in detail so as not to obscure the embodiments.

[0022] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] Liquid crystal displays (LCDs) are widely used in display instruments due to their excellent characteristics such as low operating voltage, long lifespan, low power consumption, easy integration, low electromagnetic radiation, and large display information capacity. However, due to the unique imaging principle of LCD screens, their display effect is relatively limited and cannot meet the application needs of the market. Existing solutions for adjusting LCD grayscale are achieved by adjusting the driving voltage, but the grayscale levels are limited by the electrical characteristics of the screen and cannot select local pixels for grayscale control. Furthermore, existing software solutions are only applicable to screens with a 1 / 2 BIAS resolution, and the control program is relatively complex and lacks versatility.

[0024] To address the aforementioned technical problems, this application provides a control circuit for screen display. By changing the total number of frames per unit time and the number of displayed frames per unit time, the frame display enable signal can be altered, thereby changing the time it takes for the LCD screen to display a pattern per unit time to achieve grayscale adjustment. Utilizing the principle of visual persistence, display effects such as gradual brightening, gradual dimming, and breathing can be achieved, making grayscale control no longer limited by the electrical specifications of the LCD screen, greatly reducing the complexity of software control and providing a good visual experience.

[0025] like Figure 1As shown, the control circuit for screen display includes a first counter, a second counter, a comparator, a first data selector, a second data selector, a first AND gate, a second AND gate, and a SEG terminal level selection signal generator. The first input of the comparator is connected to the first counter and receives the total frame count value per unit time output by the first counter. The second input of the comparator is connected to the second counter and receives the display frame count value per unit time output by the second counter. The comparator compares the total frame count value per unit time with the display frame count value per unit time, and then transmits the comparison result to the address selection terminal of the first data selector through the output of the comparator. The first data selector selects a corresponding preset signal as a frame display enable signal based on the comparison result output by the comparator and transmits it to the first AND gate. The frame display enable signal indicates that the current frame is... Whether an image needs to be displayed; the first AND gate receives the frame display enable signal output from the first data selector and the externally input LCD screen display data and performs an AND operation, then transmits the AND operation result to the first input terminal of the second data selector; the second AND gate receives the COM terminal breathing enable and the SEG terminal breathing enable and performs an AND operation, then transmits the AND operation result to the address selection terminal of the second data selector; the second input terminal of the second data selector is used to receive the externally input LCD screen display data, and the second data selector selects the LCD screen display data or the AND operation result of the first AND gate as the input of the SEG terminal level selection signal generator according to the AND operation result of the second AND gate; the SEG terminal level selection signal generator is used to generate a corresponding SEG terminal level selection signal according to the LCD screen display data or the AND operation result of the first AND gate, and the SEG terminal level selection signal is used to control the grayscale of the LCD screen.

[0026] It should be noted that the LCD screen is controlled by two different sets of pins: a common electrode (COM terminal) for controlling horizontal pixels and a segment electrode (SEG terminal) for controlling vertical pixels. Currently, the most common control method is line-by-line scanning, which involves periodically turning on the COM terminal to control the first row of pixels, then the second row, and so on in a cyclical manner. Combined with the control signal from the SEG terminal, all pixels can be controlled. Therefore, the main function of the control circuit for screen display is to output a level selection signal from the SEG terminal to control the grayscale of the LCD screen.

[0027] Reference Figure 1The SEG terminal level selection signal is a waveform signal generated based on the data displayed on the LCD screen. Clearly, when the address selection terminal of the second data selector receives a low level (0), the second data selector selects the LCD screen display data to the SEG terminal level selection signal generator. In this way, the LCD screen displays the original data without a breathing effect (note: the main application of grayscale control is the display of a breathing effect). Conversely, when the address selection terminal of the second data selector receives a high level (1), the second data selector selects the result of the AND operation between the LCD screen display data and the frame display enable signal. The frame display enable signal has two states, high and low, used to indicate whether the current frame needs to display an image. The change between high and low levels creates a breathing effect on the image displayed on the LCD screen, thus achieving grayscale control.

[0028] In one embodiment, the control circuit for screen display further includes a first register and a second register. The first register is connected to a first input terminal of the second AND gate and is used to transmit the COM terminal breathing enable to the second AND gate. The second register is connected to a second input terminal of the second AND gate and is used to transmit the SEG terminal breathing enable to the second AND gate. The COM terminal breathing enable and the SEG terminal breathing enable are used to indicate whether breathing is required at the intersection of a COM terminal and a SEG terminal.

[0029] like Figure 2 As shown in the figure, this application embodiment provides a screen driving circuit. The screen driving circuit includes the control circuit for screen display, and further includes a data reading module (lcd sram rd), a register configuration module (lcd regs), and a drive control signal generation module (lcd timing gen). The data reading module and the register configuration module are respectively connected to the drive control signal generation module. The data reading module is used to read the liquid crystal screen display data stored in the external video memory and transmit it to the drive control signal generation module. The register configuration module is used to configure the functional parameters of the drive control signal generation module. The drive control signal generation module is used to generate a COM terminal level selection signal and a SEG terminal level selection signal according to the liquid crystal screen display data. The drive control signal generation module includes the control circuit for screen display, and the SEG terminal level selection signal is used to control the grayscale of the liquid crystal screen.

[0030] In one implementation, the data reading module is connected to a first AND gate and a second data selector to read the LCD screen display data stored in the external video memory and transmit it to the first AND gate and the second data selector. The control circuit for screen display includes the first AND gate and the second data selector.

[0031] In one implementation, the register configuration module is connected to the first counter, the second counter, the first register, and the second register, and is used to configure the functional parameters of the control circuit for screen display, wherein the control circuit for screen display includes the first counter, the second counter, the first register, and the second register.

[0032] In one embodiment, the screen driving circuit includes a video memory control module (SRAM Ctrl), which is connected to the data reading module. The video memory control module communicates with the outside via an address bus and a data bus to control the external central processing unit to read and write to the external video memory, so that the data reading module can read the LCD screen display data stored in the external video memory.

[0033] In one embodiment, the screen driving circuit includes a signal synchronization module lcd sync, which is connected to the register configuration module and the drive control signal generation module, and is used to synchronize the system clock and the operating clock of the screen driving circuit across time domains.

[0034] In one embodiment, the screen driving circuit includes an analog voltage generation module, which is connected to the drive control signal generation module and is used to output an analog voltage to drive the LCD screen according to the COM terminal level selection signal and the SEG terminal level selection signal.

[0035] like Figure 3 As shown, the screen driving circuit described in this application embodiment has the following configurable parameters: total_frames per unit time, disp_frames per unit time (i.e., the number of actual displayed image frames per unit time), disp_step (i.e., the step size of the frame rate change between adjacent unit times), and clk_lcd, the operating frequency of the screen driving circuit. If a unit time is called a grayscale update cycle, then the grayscale contrast of each grayscale update cycle can be approximately expressed as...

[0036]

[0037] Where total_frames≥disp_frames, disp_frames≥disp_step.

[0038] As mentioned above, LCD screens control pixels through scanning. To prevent flickering, the screen refresh rate should be higher than the minimum resolution of the human eye (approximately 30Hz, a priori value). During normal display, the relationship between the operating frequency of the screen driver circuit and the number of COM ports can be expressed as follows:

[0039]

[0040] Here, clk_lcd represents the operating frequency of the screen driver circuit. Therefore, in grayscale control mode, the operating frequency of the screen driver circuit depends on...

[0041]

[0042] The screen driving circuit described in this application embodiment also has the following configurable parameters: a breathing control enable lcd_breath_en, used to indicate whether the LCD screen should produce a breathing effect; a breathing effect selection signal lcd_breath_effect[1:0], used to indicate what kind of breathing effect to display, which can be selected as gradual brightening, gradual dimming, or breathing (i.e., alternating bright and dimming); a breathing mode selection signal lcd_breath_mode, used to indicate what kind of breathing mode to select, set to 0 for continuous breathing display (e.g., continuous alternation of bright and dimming, which can only be disabled by software), set to 1 for single breathing display (e.g., when the gradual dimming effect is selected, the hardware automatically disables the breathing control enable after completing one display from bright to dimming); a COM terminal breathing enable com_breath_en[x:0], used to indicate whether a certain COM terminal needs to breathe, where x depends on the number of COM ports specified in the design specification; and a SEG terminal breathing enable seg_breath_en[y:0], used to indicate whether a certain SEG terminal needs to breathe, where y depends on the number of SEG ports specified in the design specification.

[0043] It should be noted that all the configurable parameters mentioned above can be configured through registers. From the user's perspective, these configurable parameters can be configured by writing to registers. In other words, users can modify these configurable parameters to control the effect, speed, and precision of grayscale changes on the LCD screen, aiming to achieve a better visual experience and enhance the user experience.

[0044] like Figure 1 and Figure 2As shown, the initial values ​​of the first and second counters are configured by the register configuration module `lcd regs` based on externally input configuration information. The maximum count value of the first counter is `total_frames`, the total number of frames per unit time, used to indicate one grayscale update cycle; its initial value is configured to 0. The first counter reaching its maximum count is the counting condition for the second counter. However, the second counter requires different initial values ​​under different conditions to achieve different breathing effects. The initial value and counting result of the second counter depend on the breathing effect selection signal `lcd_breath_effect`, the breathing mode selection signal `lcd_breath_mode`, and the frame change step size `disp_step`. Under the gradual brightening and breathing effects, the initial value of the second counter is configured to 0. Under the gradual dimming effect, the initial value of the second counter is `disp_frames`, the number of display frames per unit time. In single breathing mode, the second counter performs a complete increment or decrement (in breathing mode, it increments first and then decrements) and then resets to zero. In continuous breathing mode, the second counter performs continuous increment or decrement operations and can only be reset by disabling the breathing control enable in software. Furthermore, the values ​​of the first and second registers are also configured by the register configuration module lcdregs based on externally input configuration information. Clearly, when either the COM terminal breathing enable or the SEG terminal breathing enable is low, the second data selector selects the original data for display, resulting in no breathing effect. Only when both the COM terminal breathing enable and the SEG terminal breathing enable are high can the intersection of a COM terminal and a SEG terminal be selected for grayscale control, thereby achieving the corresponding breathing effect.

[0045] Reference Figure 1 The comparator is used to compare the count values ​​of the first counter and the second counter in real time. In this embodiment, when the count value of the first counter is less than or equal to the count value of the second counter, the frame display enable signal is set to 1, and the image data at the corresponding time is output normally. Otherwise, the frame display enable signal is set to 0, and the image data at the corresponding time is set to 0, and the screen does not display an image. The grayscale adjustment is achieved by changing the time of the LCD screen display pattern per unit time through the frame display enable signal. By utilizing the principle of visual persistence, display effects such as gradual brightening, gradual dimming, and breathing can be achieved.

[0046] As described above, LCD screens control pixels through scanning. Based on this, this application embodiment sets up a COM port breathing enable and a SEG port breathing enable to indicate whether a certain intersection of a COM port and a certain SEG port needs to breathe. This scheme requires a register bit length equal to the number of COM ports + the number of SEG ports, occupies a small circuit area, and can control a single pixel to achieve a breathing effect. The disadvantage is that the control is not flexible enough and cannot simultaneously control multiple pixels individually. In another embodiment, a separate grayscale control enable bit is added for each pixel, meaning each pixel has its own function to control pixel brightness and pixel breathing. This scheme requires a register bit length equal to the number of COM ports × the number of SEG ports. The advantage is precise and flexible control, but the disadvantage is that it occupies more additional circuit area. Since most dot-matrix / segment LCD screens use custom patterns, the first scheme is more practical.

[0047] Due to the unique imaging principle of LCD screens, they require AC voltage driving. The average voltage across the liquid crystal molecules must be zero within a complete frame. Therefore, the breathing enable cannot be activated at any time to avoid voltage imbalance within the complete frame leading to liquid crystal molecule polarization and screen damage. Thus, it is necessary to control the timing of the breathing enable's activation and deactivation. In one embodiment, as... Figure 4 As shown, if the software enables breathing (breath_en) in the middle of a frame via the breathing enable set signal (set_breath), the hardware will generate a preset signal (set_breath_pre). Breathing will only be enabled after the frame end flag signal (frame_end_flag) goes high. The delay from when the breathing enable set signal (set_breath) becomes active until breathing enable (breath_en) is set to 1 is at most one frame. Similarly, as... Figure 5 As shown, if the software disables the breathing enable (breath_en) at the middle of a frame by clearing the breathing enable signal (clr_breath), the hardware will generate a pre-clear signal (clr_breath_pre). The breathing enable (breath_en) will only be disabled after the frame end flag signal (frame_end_flag) goes high. The delay from when the breathing enable set signal clr_breath becomes active until the breathing enable breath_en is cleared to zero is at most one frame. The method described in this embodiment avoids damage to the LCD screen and extends its lifespan.

[0048] This application embodiment also provides a chip and a screen. The chip includes the screen driving circuit. The chip can be assembled in the screen (such as an LCD screen), so that the LCD screen can change the frame display enable signal by changing the total number of frames per unit time and the number of displayed frames per unit time, thereby changing the time for the LCD screen to display the pattern per unit time to achieve grayscale adjustment. Utilizing the principle of visual persistence, display effects such as gradual brightening, gradual dimming, and breathing can be achieved, so that grayscale control is no longer limited by the electrical specifications of the LCD screen, greatly reducing the complexity of software control and providing a good visual experience.

[0049] Obviously, the above embodiments are only some embodiments of this application, not all embodiments, and the technical solutions of various embodiments can be combined with each other. Furthermore, if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" appear in the embodiments, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. If terms such as "first," "second," and "third" appear in the embodiments, it is for the convenience of distinguishing related features, and should not be construed as indicating or implying their relative importance, order, or number of technical features.

[0050] Furthermore, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0051] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents. The above descriptions are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A control circuit for screen display, characterized in that, The control circuit for screen display includes a first counter, a second counter, a comparator, a first data selector, a second data selector, a first AND gate, a second AND gate, and a SEG terminal level selection signal generator. The maximum count value of the first counter is the total number of frames per unit time, and its initial value is configured to 0; the first counter reaching its full count is the counting condition for the second counter; under the gradual brightening and breathing effects, the initial value of the second counter is configured to 0; under the gradual dimming effect, the initial value of the second counter is the number of display frames per unit time. The first input terminal of the comparator is connected to the first counter and is used to receive the total frame count value output by the first counter within a unit time. The second input terminal of the comparator is connected to the second counter and is used to receive the display frame count value output by the second counter within a unit time. The comparator is used to compare the total frame count value within a unit time with the display frame count value within a unit time, and then transmit the comparison result to the address selection terminal of the first data selector through the output terminal of the comparator. The first data selector selects a corresponding preset signal as a frame display enable signal based on the comparison result output by the comparator and transmits it to the first AND gate. The frame display enable signal is used to indicate whether the current frame needs to display an image. The first AND gate receives the frame display enable signal output by the first data selector and the externally input LCD screen display data, performs an AND operation, and then transmits the AND operation result to the first input terminal of the second data selector. The second AND gate receives the COM end breathing enable and the SEG end breathing enable and performs an AND operation, and then transmits the AND operation result to the address selection end of the second data selector; The second input terminal of the second data selector is used to receive externally transmitted liquid crystal screen display data. The second data selector selects the liquid crystal screen display data or the AND operation result of the first AND gate as the input of the SEG terminal level selection signal generator according to the AND operation result of the second AND gate output. The SEG terminal level selection signal generator is used to generate a corresponding SEG terminal level selection signal based on the data displayed on the liquid crystal screen or the AND operation result of the first AND gate. The SEG terminal level selection signal is used to control the grayscale of the liquid crystal screen.

2. The control circuit for screen display according to claim 1, characterized in that, The control circuit for screen display further includes a first register and a second register, wherein... The first register is connected to the first input of the second AND gate, and is used to transmit the COM enable signal to the second AND gate. The second register is connected to the second input of the second AND gate and is used to transmit the SEG breathing enable to the second AND gate.

3. A screen driving circuit, characterized in that, The screen driving circuit includes the control circuit for screen display as described in any one of claims 1 to 2, and the screen driving circuit further includes a data reading module, a register configuration module, and a drive control signal generation module, wherein... The data reading module and the register configuration module are respectively connected to the drive control signal generation module. The data reading module is used to read the LCD screen display data stored in the external video memory and transmit it to the drive control signal generation module. The register configuration module is used to configure the functional parameters of the drive control signal generation module. The drive control signal generation module is used to generate a COM terminal level selection signal and a SEG terminal level selection signal according to the LCD screen display data. The drive control signal generation module includes the control circuit for screen display, and the SEG terminal level selection signal is used to control the grayscale of the LCD screen.

4. A screen driving circuit according to claim 3, characterized in that, The data reading module is connected to a first AND gate and a second data selector, and is used to read the LCD screen display data stored in the external video memory and transmit it to the first AND gate and the second data selector. The control circuit for screen display includes the first AND gate and the second data selector.

5. A screen driving circuit according to claim 3, characterized in that, The register configuration module is connected to the first counter, the second counter, the first register, and the second register, and is used to configure the functional parameters of the control circuit for screen display. The control circuit for screen display includes the first counter, the second counter, the first register, and the second register.

6. A screen driving circuit according to claim 3, characterized in that, The screen driving circuit includes a video memory control module, which is connected to the data reading module. The video memory control module communicates with the outside via an address bus and a data bus to control the external central processing unit to read and write to the external video memory, so that the data reading module can read the LCD screen display data stored in the external video memory.

7. A screen driving circuit according to claim 3, characterized in that, The screen driving circuit includes a signal synchronization module, which is connected to the register configuration module and the drive control signal generation module, and is used to synchronize the system clock and the operating clock of the screen driving circuit across time domains.

8. A screen driving circuit according to claim 3, characterized in that, The screen driving circuit includes an analog voltage generation module, which is connected to the drive control signal generation module and is used to output an analog voltage to drive the LCD screen according to the COM terminal level selection signal and the SEG terminal level selection signal.

9. A chip, characterized in that, The chip includes the screen driving circuit according to any one of claims 3 to 8.

10. A screen, characterized in that, The screen includes the chip of claim 9.

Images