JPH11119739A - Display data storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the total storage capacity of a mask ROM and a flash memory by writing the dot data for a character fixed or having a low probability of revision in the mask ROM and writing the dot data for a character having a high probability of revision in the flash memory. SOLUTION: The mask ROM 7 or the flash memory 8 is address-specified by a CPU 2 according to the decoding result of the program data read out from a ROM 1, and the dot data read out from the mask ROM 7 or the flash memory 8 are held to a register in the CPU 2. Thereafter, a display ROM 5 is address specified by the CPU 2, and the dot data held to the CPU 2 are written in the display ROM 5. In such a case, the dot data for the character fixed or having a low probability of revision are written in the mask ROM 7, and the dot data for the character having a high probability of revision are written in the flash memory 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display data storage device suitable for use in a microcomputer having a display drive circuit such as a liquid crystal.

[0002]

2. Description of the Related Art In recent years, electronic equipment with a liquid crystal panel has been widely used. Display of characters (characters, numbers, pictures, etc.) on the liquid crystal panel is realized by using a microcomputer having a built-in liquid crystal drive circuit. Characters that can be confirmed on the liquid crystal panel are an aggregate of lighting and extinguishing in dot units. In the liquid crystal drive circuit, dot data for a character (logical value “1” when lit, logical value “0” when lit) is stored in an address corresponding to the display position of the liquid crystal panel on a one-to-one basis. It has a display RAM. The dot data for all the characters displayed on the liquid crystal panel is stored in the mask ROM as table data. When the display state of the character on the liquid crystal panel is changed, dot data corresponding to the change in the display state of the character is read from the mask ROM according to the result of decoding the program data read from the ROM, and the contents of the display RAM are read. The operation of rewriting was repeated. The mask ROM may or may not be built in the microcomputer.

[0003]

The mask RO
M has a structure in which data of a logical value “1” or a logical value “0” is printed in advance by using a plurality of masks in a manufacturing process of an integrated circuit, so that once printed data cannot be rewritten. Therefore, dot data for all characters displayed on the liquid crystal panel is written in the mask ROM. However, when the number of character changes is large, the storage capacity of the mask ROM increases in response to the number of character changes, and there is a problem that the integrated circuit becomes large. In addition, since changing the data in the mask ROM requires a large amount of development cost and a long development time, it is desirable that the mask ROM for liquid crystal display can be shared between a plurality of types of electronic devices with liquid crystal panels. However, when the mask ROM is shared, versatility can be obtained, but on the other hand, some types of electronic devices
A disadvantage arises in that dot data for character display required by other types of electronic devices must be shared although unnecessary.

A static RAM has a characteristic that data can be rewritten, and can be used instead of a mask ROM. However, since it is volatile, it is not practical. Therefore, an object of the present invention is to provide a display data storage device that can prevent the chip area from increasing even if the number of character changes increases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises a CPU;
A ROM in which program data for controlling the operation of the PU is stored, a display drive circuit for displaying a character on a display panel according to an instruction from the CPU, and a character to be displayed on the display panel according to an instruction from the CPU A display RAM in which dot data to be stored is stored at an address corresponding to the display position of the display panel on a one-to-one basis, wherein dot data constituting all the characters displayed on the display panel is stored. A read-only first non-volatile memory in which dot data constituting a character to be displayed on the display panel is read out as data stored in the display RAM in accordance with an instruction from the CPU; A second nonvolatile memory capable of writing and reading, 1 The non-volatile memory stores dot data for fixed characters or dot data for characters that are unlikely to be changed, and the second non-volatile memory has a high possibility of change. It is characterized by storing dot data for a character.

The first nonvolatile memory has a mask R
OM, wherein the second non-volatile memory is a flash memory, and is allocated to the same address space.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be specifically described with reference to the drawings. FIG. 1 is a block diagram showing a display data storage device according to the present invention. In FIG. 1, (1) is a ROM
And program data for controlling the arithmetic processing operation of the microcomputer.
Reference numeral (2) denotes a CPU which executes various arithmetic processes in accordance with the result of decoding the program data read from the ROM (1). The CPU (2) includes a program counter, an instruction register, an instruction decoder, an accumulator, an arithmetic logic unit, and the like. (3) is a liquid crystal panel in which a plurality of common electrodes and a plurality of segment electrodes are arranged in a matrix. The intersection of the common electrode and the segment electrode is the position where the dot is turned on or off. A liquid crystal driving circuit (4) is a liquid crystal driving circuit that selects one of a plurality of common electrodes constituting the liquid crystal panel (3) according to dot data read from the display RAM (5). And a segment drive signal for selecting any one of the plurality of segment electrodes constituting 3). The intersection of the selected common electrode and segment electrode of the liquid crystal panel (3) is turned on. (5) is display RAM
And characters (characters, numbers,
The dot data (logical value "1" when the dot is turned on, and logical value "0" when the dot is turned off) for displaying a picture or the like is written. Note that the address of the display RAM (5) has a one-to-one correspondence with the display position of the liquid crystal panel (3), and the written contents of the display RAM (5) change the display state of the character on the liquid crystal panel (3). It is rewritten every time.
(6) a liquid crystal control circuit for setting a clock frequency for liquid crystal display, adjusting contrast for liquid crystal display, controlling on / off of liquid crystal display, setting the number of dots in the horizontal and vertical directions of liquid crystal display, etc. Is what you do. The operation clock of the liquid crystal control circuit (6) and the operation clock of the CPU (2) are independent, and the liquid crystal control circuit (6) is used for the read operation of the display RAM (5).

A mask ROM (7) stores dot data for a fixed character or dot data for a character with a low possibility of change among all characters displayed on the liquid crystal panel (3). It was baked with a mask. (8) is a flash memory, which has a non-volatile characteristic that allows data to be collectively or partially erased and written and read out, and is capable of changing all characters displayed on the liquid crystal panel (3). The dot data for the character having high character is written. The mask ROM (7) and the flash memory (8) are allocated to the same address space as a memory for storing table reference data.

When the contents of the display RAM (5) are rewritten, the mask ROM (7) or the flash memory (8) is addressed by the CPU (2) according to the result of decoding the program data read from the ROM (1). The designated dot data read from the mask ROM (7) or the flash memory (8) is held in a register inside the CPU (2). After that, the display RAM (5) is
The dot data addressed by (2) and held in the CPU (2) is written to the display RAM (5). The rewriting operation of the dot data of the display RAM (5) is performed in advance in synchronization with the timing of changing the character of the liquid crystal panel (3).

According to the embodiment of the present invention, the storing of dot data for all characters displayed on the liquid crystal panel (3) in only the mask ROM is stopped, and the dot data for fixed characters is stopped. Alternatively, dot data for a character having a low possibility of change is written to the mask ROM (7), and dot data for a character having a high possibility of change is written to the flash memory (8). Thus, when manufacturing a plurality of electronic devices having different liquid crystal display specifications, dot data for a character different among the plurality of electronic devices may be written into the flash memory (8) provided for each electronic device. The problem that two electronic devices have dot data for unnecessary characters can be solved, and the total storage capacity of the mask ROM (7) and flash memory (8) that store dot data for characters as table reference data can be reduced. Can be reduced compared to

[0011]

According to the present invention, dot data for all characters displayed on the display panel is stored in the mask ROM.
Only, and write dot data for fixed characters or dot data for characters that are unlikely to be changed into the mask ROM, and dot data for characters that are likely to be changed. Was written to the flash memory. From this, when manufacturing a plurality of electronic devices having different display specifications, dot data for a character different among the plurality of electronic devices may be written in a flash memory provided for each electronic device,
It is possible to solve the problem that one electronic device has dot data for an unnecessary character, and a mask RO that stores dot data for a character as table reference data.
There is an advantage that the total storage capacity of the M and the flash memory can be reduced as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a display data storage device according to the present invention.

[Explanation of symbols]

 (3) Liquid crystal panel (5) Display RAM (7) Mask ROM (8) Flash memory

Claims (2)

[Claims] A CPU that stores program data for controlling the operation of the CPU;
A display driving circuit for displaying a character on the display panel according to an instruction from the CPU, and an address corresponding to a display position of the display panel in one-to-one correspondence with dot data constituting a character to be displayed on the display panel according to an instruction from the CPU. And a display RAM stored in the microcomputer. In the microcomputer, dot data constituting all the characters displayed on the display panel is stored, and a character to be displayed on the display panel is constituted according to an instruction from the CPU. A read-only first non-volatile memory from which dot data is read as data stored in the display RAM; and a second non-volatile memory capable of batch or partial electrical erasure and writing / reading; The non-volatile memory contains dot data or changes for fixed characters. Wherein dot data for a character having a low possibility of being stored is stored, and dot data for a character having a high possibility of being changed is stored in the second nonvolatile memory. Storage device. 2. The method according to claim 1, wherein the first nonvolatile memory has a mask RO.
2. The display data storage device according to claim 1, wherein the second nonvolatile memory is a flash memory, and is assigned to the same address space.