JPS649635B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device that displays characters as dots. More specifically, the present invention relates to display control for uppercase letters in a display device that can display characters (referred to as uppercase letters) that are several times larger than normal letters.

There are display devices that can display, in addition to normal characters, uppercase letters (for example, kanji) that are the size of two normal characters, but they have had the following problems. In conventional devices of this type, control codes for character modification are stored in a refresh memory together with character codes. And when displaying,
The control code read together with the character code from the refresh memory determines whether the character code is a normal character or an uppercase character, and if it is an uppercase character, whether the character code is for the left half or the right half of the uppercase character. Identify and dots from character generator
Controls the generation of data.

In such a display control method, it is necessary to set both a character code and a control code when writing to the refresh memory, which causes disadvantages such as complicating the program and increasing the amount of hardware in the device. It was hot.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a display device using a display control method that can overcome the above-mentioned drawbacks.

However, according to the present invention, the refresh memory of the display device does not store anything like conventional control codes, but instead stores two uppercase character codes (this means that uppercase letters are displayed as two normal characters). In general, if you want to display n characters, then n characters)
Store continuously. In addition, the display device
It is determined whether the character code read from the refresh memory is for a normal character or an uppercase character, and based on the result, the generation of dot data in the character generator is controlled as follows. That is,
In the case of a character code of a normal character, dot data of the corresponding character is generated by a character generator. On the other hand, in the case of an uppercase character code, depending on whether the character code is the first or second one, the dot data of the left half of the uppercase character is read out according to the character code read first. , and in accordance with the character code to be read next, dot data for the right half of the uppercase character is generated by a character generator. Generalizing, for each of the 1st to nth consecutively read same character codes,
A character generator sequentially generates dot data for each part of the uppercase character divided into n parts in the horizontal direction. If character codes are defined such that normal characters and uppercase characters can be distinguished by the value of one or several bits in the character code, complicated hardware is not required.

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the main parts of a display device embodying the present invention.

The device of this embodiment can display normal characters and uppercase characters the size of which are two characters larger. The character code is 1
Bytes (8 bits), and the character code for normal characters is defined as the most significant bit being "0", and the character code for uppercase letters is defined as the most significant bit being "1". Of course, in general, the character code may be any number of bits.
Character codes are stored in the refresh memory 1 by a program and read out sequentially in synchronization with screen scanning. Note that the uppercase character code is written in two bytes at consecutive addresses.

Reference numeral 11 denotes a control circuit for controlling the character generator 12 by identifying whether a character code read from the refresh memory 1 is a normal character or an uppercase character, and is comprised of a flip-flop 3 and gates 2, 4, and 5. Trigger synchronized with reading of refresh memory 1.
Clock 9 and the most significant bit of the character code are input to AND gate 2, and the output of AND gate 2 triggers flip-flop 3. The flip-flop 3 has a data input D and an inverted output coupled together. Therefore, when the first byte character code of an uppercase character is read from the refresh memory 1, the flip-flop 3 is set at the rising edge of the trigger clock 9 at that time, and the trigger clock when reading the second byte character code is set. At the rising edge of clock 9, flip-flop 3 is reset. 1
0 is the initial reset signal for flip-flop 3. That is, the flip-flop 3 has the function of storing, when an uppercase character code is read from the refresh memory 1, whether the character code is the first byte or the second byte of two consecutive bytes. are doing.

The character generator 12 is composed of memories 6, 7, and 8, where memory 6 stores dot data for normal characters, memory 7 stores dot data for the left half of uppercase characters, and memory 8 stores dot data for the right half of uppercase characters. are stored respectively. The most significant bit (1
The remaining 7 bits are supplied to the chip select input of memory 6, and the remaining 7 bits are supplied to address inputs A4-A10 of each memory 6, 7, and 8, respectively. The chip select input of the memory 7 is supplied with the output of a NAND gate 4 into which the most significant bit of the character code and the non-inverted output Q of the flip-flop 3 are input. Memory 8 chip select input
CS is supplied with the output of a NAND gate 5 into which the most significant bit of the character code and the inverted output of the flip-flop 3 are input. In addition, each memory 6, 7,
A row address signal 12 from a row counter (not shown) is input to address inputs A0 to A3 of No. 8. The dot data output in parallel from each of the memories 6, 7, and 8 is converted into serial data and sent to the display section, but since this point is not directly related to the present invention, its explanation will be omitted.

Next, the operation of this embodiment will be explained with reference to the time chart shown in FIG. Note that "A, B, C, D" are the character codes of normal characters, and "Kan" is the character code of uppercase letters (for example, Kanji).

When character code "A" is read from refresh memory 1, its most significant bit is "0", so memory 6 is selected and the corresponding character (regular character) is selected from the address determined by the lower 7 bits of this character code. ) is read out. The same applies to the next character code B.

When the first byte of the character code "Kan" is read out, the flip-flop 3 is set and the output of the NAND gate 4 becomes "0". Therefore, memory 7
is selected, and the dot data of the left half of the corresponding capital letter is read from the address specified by the lower seven bits of the character code "Kan". At this time, since the output of the NAND gate 5 and the most significant bit of the character code are "1", the other memories 6 and 8 are not selected. Then, when the second byte is read, the flip-flop 3 is reset and the output of the NAND gate 5 becomes "0". Therefore, memory 8 is selected and the dot data of the right half of the capital letter is read out.

For character codes "C" and "D", the memory 6 is selected as described above, and dot data is read out.

As described above, the present invention eliminates the need for control codes for character modification as in the past, reducing the burden on the program, and distinguishing between normal characters and uppercase letters and controlling the character generator as described above. It can be realized with a simple circuit and has many advantages, such as reducing the amount of hardware required for the display device. Furthermore, in the present invention, it is only necessary to allocate at most one identification bit in a character code to indicate whether the character code is a normal character or an uppercase character, and when one uppercase character is displayed with n identical character codes, ,
There is no need to allocate identification bits in the character code to indicate which part of the uppercase character the character code belongs to, and the effect of increasing the number of bits that can be defined as the original character code can also be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of a display device according to an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the same embodiment. 1... Refresh memory, 2... AND gate, 3... Flip-flop, 4, 5... NAND gate, 6, 7, 8... Memory, 11... Control circuit, 12... Character generator.

Claims (1)

[Scope of Claims] 1. A refresh memory that stores a plurality of character codes, a character generator that generates dot data corresponding to character codes read from the refresh memory, and controls the operation of the character generator. In a display device that displays characters in dots, the character code stored in the refresh memory is either the character code of a normal-sized character (hereinafter referred to as a normal character) or the character code of a normal-sized character. n characters (n
contains an identification bit that indicates the character code of a character (hereinafter referred to as an uppercase letter) with a size of A configuration is adopted in which n identical character codes are assigned and the n identical character codes are successively stored in a refresh memory, and the character generator generates dot data of a normal character corresponding to one character code. Corresponding to the first character generation part that generates and each of the n character codes,
The control circuit is configured to determine whether the character code read from the refresh memory is a normal character or an uppercase character. means for identifying a character code for a capital letter, means for storing the order of consecutive n identical character codes when a character code for an uppercase letter is identified, and means for operating the first character generation section in the case of a character code for a normal character. , in the case of uppercase character codes, means for sequentially operating the n second character generation units in accordance with the order of n identical character codes successively read from the refresh memory. A display device featuring: