KR19990025536A - LCD Graphics Driver with Embedded Fonts - Google Patents

Abstract

Disclosed are a liquid crystal graphics driver having a built-in font. According to the present invention, there is provided a liquid crystal graphic driver in which a text message is embedded. A clock signal generator for generating an internal clock signal in response to the clock signal; a display data RAM for storing predetermined character data or graphic data input from a microprocessor and outputting data to a liquid crystal display in response to a command of the microprocessor; A display data RAM address counter for counting the address of the display data RAM in response to the signal, storing predetermined character font data, and displaying the character font data corresponding to the ROM address input from the microprocessor. A character ROM to output the character ROM; Characterized in that it comprises a.

Description

LCD graphics driver with built-in character ROM

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic driver, and more particularly, to a liquid crystal graphic driver having a character ROM embedded therein.

With the development of communication means and the development of portable information communication devices, the need for liquid crystal devices (LCDs) for outputting necessary information on the screen continues to increase. The small liquid crystal display device can be largely divided into a character type LCD and a graphic type LCD. The LCD driver for characters stores required characters or symbols in an internal font (ROM) ROM and specifies the address of each character in the microprocessor unit (MICROPROCESSOR UNIT: MPU) to output the character data. Mainly used. In addition, in the case of a liquid crystal driver for RAM embedded graphics, the MPU stores graphics data to be displayed on the LCD in the embedded graphics RAM and outputs each line of data as needed.

1 is a schematic block diagram for explaining a conventional liquid crystal graphic driver 10.

Referring to FIG. 1, the conventional liquid crystal graphic driver 10 may include an MPU interface unit 170, a controller 150, a clock signal generator 160, a DDRAM (Diplay Data RAM) 140, and a DDRAM address counter 130. ), An output driver 120, and controls to display a predetermined character or graphic on the LCD 12 in response to a control command of the MPU 14. The output driver 120 includes a shift register 124, a COM (COMMON) signal driver 122, a data latch unit 128, and a SEG (SEGMENT) signal driver 126.

As shown in FIG. 1, the RAM embedded LCD driver 10 inputs data and control signals through the MPU interface unit 170. The controller 150 converts the input control signal into a control signal for controlling the internal block and outputs the converted control signal. The input data is stored as display data at a predetermined position via the DDRAM address counter 130. This data is output to the data latch unit 128 and latched, and is output to the LCD 12 through the SEG signal driver 126 in synchronization with an internal output signal. The COM signal output from the COM signal driver 122 enables each line on which data to be actually output is output.

In general, the conventional liquid crystal graphic driver 10 having a built-in RAM stores character data or graphic data transferred from the MPU 14 in the internal DDRAM 140, and when each COM signal is enabled, through each SEG terminal. The LCD 12 is driven by outputting data of lines. In addition, since the conventional liquid crystal graphic driver 10 used the character font data and the graphic data without distinguishing them, the MPU 14 had to transmit all data to be displayed to the liquid crystal graphic driver 10.

FIG. 2 is a diagram for explaining a process of writing character font data in the conventional liquid crystal graphic driver 10. As shown in FIG.

That is, FIG. 2 shows the relationship between the MPU interface command output from the MPU 14 and the data stored in the DDRAM 140 when the conventional liquid crystal graphic driver 10 intends to display a 6 * 8 size letter 'A'. In order to display the letter 'A', all necessary font data must be transferred from the MPU 14, and font data is applied to the MPU interface unit 170 via an 8-bit data bus, and an address counter ( 130 is written to DDRAM 140.

As a result, in order to display predetermined characters on the LCD 12 using the conventional liquid crystal graphic driver 10, the MPU 14 must transmit all character font data to the liquid crystal graphic driver 10. There is a problem that the number of interfaces increases, and the microcomputer program for the interface becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a liquid crystal graphic driver with a built-in character ROM having a character ROM therein for storing font data of frequently used characters.

1 is a schematic block diagram for explaining a conventional liquid crystal graphics driver.

FIG. 2 is a diagram for explaining writing of font data performed in the conventional liquid crystal graphic driver shown in FIG.

3 is a schematic block diagram illustrating a liquid crystal graphics driver incorporating a character ROM according to the present invention.

FIG. 4 is a diagram for explaining character font data writing performed in the liquid crystal graphic driver shown in FIG.

In order to achieve the above object, a liquid crystal graphic driver with a built-in character ROM according to the present invention is a liquid crystal graphic driver for controlling display of a predetermined character or graphic on a liquid crystal display device in response to a control command input from a microprocessor. A clock signal generator which generates an internal clock signal in response to a control command of the microprocessor, and stores predetermined character data or graphic data input from the microprocessor and outputs the data to the liquid crystal display in response to the command of the microprocessor. A display data RAM address counter for counting the address of the display data RAM in response to a clock signal, a predetermined character font data, and a character font corresponding to a ROM address input from the microprocessor. In response to the character ROM, and the clock signal for outputting other data to the display RAM and is preferably configured as a ROM decoder for decoding the address of the character ROM.

Hereinafter, a liquid crystal graphic driver having a character ROM according to the present invention will be described with reference to the accompanying drawings.

3 is a schematic block diagram illustrating a liquid crystal graphics driver incorporating a character ROM according to the present invention.

Referring to FIG. 3, the liquid crystal graphic driver 30 having a character ROM according to the present invention may include an MPU interface unit 370, a controller 350, a DDRAM address counter 330, a DDRAM 340, and a clock signal generator. 360, the character ROM 380, the ROM decoder 390, and the output driver 370 serve to interface between the MPU 34 and the LCD 32. Here, the output driver 320 includes a COM signal driver 322, a shift register 324, a SEG signal driver 326, and a data latch unit 328.

The MPU interface unit 370 of the liquid crystal graphic driver 30 illustrated in FIG. 3 receives predetermined data or control commands from the MPU 370 and transfers them to an internal block, or transmits internal data or response signals to the MPU 34. To pass). Also, the MPU 34 writes data to be written to the LCD 32 with the predetermined control command to the DDRAM 340, and reads the data written to the DDRAM 340 again through the MPU interface unit 370. By doing this, the graphic driver 30 checks whether the correct data is transmitted to the LCD 32. That is, the DDRAM 340 performs a READ / WRITE interface with the MPU 34 through the MPU interface 370 to display predetermined characters or graphics of the liquid crystal graphic driver 30. That is, the MPU 34 writes characters to be displayed in the RAM inside the liquid crystal graphics driver in response to the write enable signal.

The control unit 350 converts the control command input through the MPU interface unit 170, that is, the control signal into a control signal for controlling each internal block, and outputs the converted control signal in response to the clock signal CK. By turning on / off the LCD display. The DDRAM address counter 330 counts the DDRAM address input through the MPU interface unit 370 and the control unit 350, and the counted address is responsive to the clock signal CK generated by the clock signal generator 360. It is output to the DDRAM 340. The DDRAM 340 stores the data output from the MPU 34 at a predetermined position corresponding to the DDRAM address indicating which position to write. That is, the data input from the MPU 34 is stored as display data at a predetermined position through the DDRAM address counter 130. The clock signal generator 360 generates a predetermined oscillation frequency signal in response to a clock control signal applied from the MPU 34, and synchronizes the controller 350, the DDRAM address counter 330, and the ROM decoder 390, respectively. The first clock signal CK1, the second clock signal CK2, and the third clock signal CK3 are generated. That is, the DDRAM address counter 330 inputs a write / read enable signal from the control unit 350, and responds to the address of the DDRAM 340 in response to the second clock signal CK2 applied from the clock signal generator 360. Counts. The DDRAM 340 outputs predetermined data written in response to the read enable signal and the write enable signal to the output signal driver 320, or writes new data output from the MPU 34. As described above, since character data that is frequently used to display characters on the LCD 32 is stored in the character ROM 380, the MPU 34 specifies only the address of the character data, and the ROM decoder 390. ROM data of the position corresponding to the decoded address is transferred to the DDRAM 340.

The character ROM 380 stores frequently used character font data, and outputs data of a designated address corresponding to the ROM address output from the MPU 34 to the DDRAM 340. The ROM decoder 390 decodes this ROM address and outputs it to the character ROM 380.

In addition, the output driver 320 includes a COM signal driver 322, a shift register 324, a data latch unit 328, and a SEG signal driver 326. The COM signal driver 322 is controlled by the controller 350. The output control signals are shifted in the shift register 324 to be converted into several bits of parallel data, and the converted parallel data is input to generate a COM signal. As described above, the COM signal enables each line on which data to be actually output is output. In addition, the data stored in the DDRAM 340 are latched by the data latch unit 328 and output to the SEG signal driver 326. The latch data input to the SEG signal driver 326 is output to the LCD 32 line by line in response to an internal output signal, and displays characters or graphics to be displayed on the LCD 32.

As described above, since character data that is frequently used to display characters on the LCD 32 is stored in the character ROM 380, the MPU 34 specifies only the address of the character data, and the ROM decoder 390. ROM data of the position corresponding to the decoded address is transferred to the DDRAM 340.

FIG. 4 is a diagram for explaining writing of font data in the liquid crystal graphic driver shown in FIG.

Referring to FIG. 4, a description is given of writing font data for displaying one letter 'A', and the font for 'A' of the character ROM 38 of the liquid crystal graphic driver 30 in the MPU 380. When only the address of the data is transmitted, the ROM decoder 370 decodes the input address and outputs it to the character ROM 380. Accordingly, the character ROM 380 transfers font data necessary for representing a character to be written to the RAM to the DDRAM 340, and the desired letter 'A' is written in the DDRAM 340.

If the data to be displayed on the DDRAM 340 is written, each data is output one line when there is an output request. That is, the written data is latched by the data latch unit 328 and then input to the SEG signal driver 326 in synchronization with an internal output signal, and is output through the SEG terminal and displayed on the LCD 320. In addition, the control signals input from the control unit 350 are converted into parallel data in the shift register 324 and generated as a COM signal of a few bits. The COM signal is input to the COM signal driver 322 to enable each line when outputting the SEG signal. Therefore, the LCD 32 displays the desired screen by using the COM signal / SEG signal output from the liquid crystal graphic driver 30.

According to the present invention, not only can the number of interfaces between the MPU and the liquid crystal graphic driver be reduced, but also the program of the MPU for the interface can be reduced to a much smaller size.

Claims (1)

A liquid crystal graphic driver for controlling display of a predetermined character or graphic on a liquid crystal display device in response to a control command input from a microprocessor. A clock signal generator configured to generate an internal clock signal in response to a control command of the microprocessor; A display data RAM for storing predetermined character data or graphic data input from the microprocessor and outputting the data to the liquid crystal display in response to a command of the microprocessor; A display data RAM address counter for counting an address of the display data RAM in response to the clock signal; A character ROM storing predetermined character font data and outputting character font data corresponding to a ROM address input from the microprocessor to the display data RAM; A ROM decoder for decoding the address of the character ROM in response to the clock signal; And And an output signal driver converting the data stored in the display data RAM into a segment signal and outputting the segment signal when a common signal is enabled.