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The principle of LCD control circuit

Paper source:StationPopularity:29Time:2015-04-24SmallIn Big

The principle of the 1 LCD control circuit

Liquid crystal display control for LCD driver control, the controller belongs to the computer I/O interface, controlled by MPU, the manipulation of the LCD driver, to achieve in the dot matrix liquid crystal display device on a variety of display function.

It makes use of MPU to get rid of the display and control of complex, the dot matrix liquid crystal display device is more suitable for the intelligent system. The controller of the characteristics can be summarized as follows:

The MPU interface is simple, showing the general characteristics of general parallel interface controller on MPU.

It has a complete set of logic control circuit and a timing generator, can complete the display buffer management function and achieve the control of various functions.
The complete set of which possess the function of control, can be easily implemented in MPU on the controller and LCD display function by programming control device.
The display data transmission capacity and the ability to send pulse signal, can directly control the LCD driver.

In the structure of liquid crystal display control can be divided into the interface part, control part and output part is composed of three parts.

(1) interface

An interface to receive MPU sent the instructions and data, and feedback the information to the data required by MPU. Interface with two channels, one for the command port; another is the data channel. Command channel port is used to receive and store of MPU code, for the controller logic decoding in order to achieve the corresponding functions. The channel is connected "busy" (busy) flag register. Mark "busy" represents the current controller of internal operation state. MPU can be read through the instructions to remove the "busy" channel logo, used to determine when the controller operation. The data channel is used to send and receive data. MPU can access data channel display buffer, supplementary controller instruction with parameters, such as the address of a pointer cursor settings, enter the address parameter to follow the two bytes of the instruction set. This parameter must through the data channel transmission parameters corresponding to the register, the instruction code is code register to register all kinds of parameters, strobe.

In addition to the Department of the interface leads to a 8 bit data bus, and a control signal input lines, such as read and write control signal, the chip select signal, channel selection signal, enable signal and a reset signal, the controller of a certain type of interface and signal lines are designed to adapt to a series of MPU.

(2) control

Liquid crystal display controller has the independent ability of information processing. Circuit implementation is the ability to control the liquid crystal display.

The timing and logic control circuit of oscillator is independent, in order to achieve the display buffer RAM and the management of the character generator set; the liquid crystal display timing pulse signal drive production, and according to some state variables of register will show a combination of different buffer data by some rules, and then sends out, in order to achieve a variety of display effect.

Any kind of display devices are needed to establish the buffer display, liquid crystal display device is no exception. In order not to occupy MPU of memory resource management ability, liquid crystal display controller with RAM. Because the buffer with the changes in the size of the picture shows the display, so that the buffer is generally not integrated in the controller but by the peripheral circuit and control the connection controller. Therefore, in addition to the power control of the pin function and some hardware settings, the display buffer management, general with 16 bit address, 8 bit data output line line, read, write the control output line.

Display buffer role is to preserve the current display data. The liquid crystal pixel dot matrix display with the corresponding unit in the area. In character mode, display buffer unit stores the current display the character code, the controller based on the code determines the character generator. The high 8 bits of the address, and a set of character font to display the corresponding position on the display. In this way, the buffer unit (a byte) corresponds to display a character block (5 * 7 dot matrix).

The controller with synthetic display, display buffer may be divided into character display and graphic display area. This division is generally the first address and to set the length of the district by setting instructions. When the buffer allocation is completed, the display area of the property is determined, and the corresponding relationship between display position is determined. On the same screen display, character display and graphic display area size ratio is 1: 8 (8 * 8 dot matrix characters when).

CGROM character generator of 100 kinds of commonly used characters, numbers, symbols of the embedded controller. In order to meet the needs of users, the ability to control should also be extended with the administration of external character generator CGRAM and CGROM, users can make use of a custom character font library in this area in order to achieve the display of special requirements.

(3) Department of drive

Driving part of the liquid crystal display module interface controller. The liquid crystal display module in the driver provides the frame of the desired signal, row, column shift pulse, row, column column display data latch pulse, signal and drive AC driving waveform signal output signal. Drive in the address pointer to refresh the display data to the display in the hybrid circuit, parallel / serial circuit into serial data output form. Pulse sequence output is generated by the time sequence generator. The liquid crystal display module to control the time
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