JPS6154231B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an undefined code detection method in a device that outputs and displays characters on a display device, printer, etc. using a character generator in which character patterns are stored, and simplifies the circuit configuration. The purpose is to reduce costs.

Figure 1 is a block diagram showing the circuit configuration of a conventional display device.
3 is a character generator, 3 is a character pattern assembly section, 4 is a display control section, and 5 is a display section such as a CRT. When displaying characters, etc., when a character code is input from the control unit to the character generator 2, a character pattern corresponding to the character code is read from the character generator 2 and input to the character pattern assembly unit 3. . The characters are then input in the form of a character pattern to the display 5 via the display control unit 4, and the characters are displayed. However, in devices that require a large-capacity character generator, such as a kanji display device, it is not possible to store all kanji patterns in the character generator 2, so for kanji for which character patterns are not defined, Even if the code is input, the character pattern cannot be output.
When an undefined code with no defined character pattern is input into the character generator as described above, this fact is displayed as follows. That is, the table 6 stores comparison contents between character codes and characters defined in the character generator 2,
The character code is also input into this table 6 to detect whether it is a defined code or an undefined code. If it is a defined code, a corresponding character pattern is output from the character generator 2 and displayed, and if it is an undefined code, a detection signal is input to the control unit 1, and a character pattern is defined in the character generator. An undefined character code, such as a character code such as "?" or "*", indicating that the character is not registered is input to the character generator 2, and a symbol such as "?" or "*" is displayed. This allows the operator to decide whether to abandon the display of kanji characters and instead display them in kana characters or to use other kanji characters.

However, such a configuration requires a special memory for the table, resulting in high costs.
The present invention aims to solve these problems in conventional undefined code detection methods. To achieve this object, the present invention provides a character generator equipped with a storage area for storing character patterns corresponding to character codes, in which a character pattern is stored in a surplus storage area in the storage area for each character pattern. An undefined flag area is provided to indicate whether or not a character pattern is defined, and when this undefined flag indicates that a character pattern is undefined, a code indicating the pattern as an undefined code is supplied to the character generator. A control means is provided for outputting a character pattern read from the character generator in response to the undefined flag being set, and for causing the character generator to output a pattern indicating an undefined code depending on the reset state of the undefined code. A method is adopted in which the data is read out and output.

As described above, according to the present invention, since the undefined flag area is provided in the surplus area of the character pattern storage area, the pattern and the flag are stored in the same area corresponding to the character code, and it is easy to change the contents of the CG. can be done. In addition, character patterns can be read out when this flag is set to "1", while patterns indicating undefined can be automatically read out when the flag is reset to "0". It is configured to read out patterns. Therefore, a character pattern and a pattern indicating an undefined code can be generated by the same CG, and the configuration for generating a pattern indicating an undefined code can be simplified. Furthermore, the flag area set state indicates a defined code, and the flag reset state indicates an undefined code, so a flag "1" indicates a defined code, and a flag "0" indicates an undefined code. As a result, the undefined area of the character pattern in the CG becomes a "0" state, and it becomes possible to inevitably indicate undefined. Next, details of the present invention will be explained based on illustrated embodiments. FIG. 2 is a block diagram showing an example of the undefined code detection method according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals. The character pattern definition in the character generator 2' is performed using a 5.times.7 dot character font, but in such a case, an 8-bit product is usually used as the ROM for the character generator. Therefore, only seven bits bP of the ROM are used to store character patterns, for example, the lowest bit bP
bn is vacant. In the illustrated example, the vacant bit bn is used as an undefined bit, and when a character pattern corresponding to the character code is defined, a flag of logic "1" is set, for example. When the character generator 2' is read, the flag is also read at the same time.

An AND gate 7 is connected between the character generator 2' and the character pattern assembly section 3, and the read signal of the character generator 2' is outputted via the AND gate 7. Since the AND gate 7 is opened by reading the bn flag, the character pattern signal read from the character generator 2' is supplied to the character pattern assembling section 3.

A selector 8 is provided between the control unit 1 and the character generator 2'.
The character code from the control section 1 is inputted to the character generator 2' via the selector 8. Reference numeral 9 denotes a setting address board, on which codes such as "*" and "?" indicating undefined codes are set, and are inputted to the character generator 2' via the selector 8. The selector 8 is switched by the read signal of the undefined bit bn of the character generator 2'. That is, as mentioned above, the character generator 2'
Regarding the character code defined in the character code, the undefined bit flag is read and the AND gate 7 is opened, but that signal is also input to the selector 8, and the selector 8 is switched to the control unit 1 side and held. ing.

For characters that are not defined in the character generator 2', no character pattern is output even if a character code is input to the character generator 2', and a logic "1" flag is not read from the undefined bit. Therefore, the selector 8 is switched to the setting address board 9 side.
Then, from the setting address board 9, the character codes of "?" and "*" indicating undefined codes are inputted to the character generator 2' via the selector 8, and The character pattern is read out and displayed on the display 5. At this time, at the same time as reading the undefined character code, the undefined bit is
By reading the flag "1" of bn, the AND gate 7 is opened and the selector 8 is switched to the control section 1 side to prepare for the next reading. In the case of an undefined character code, in addition to displaying the undefined character code on the display to alert you,
Instead of inputting the character code of the undefined character code, only the digit position on the display 5 may be advanced by one digit to display a so-called space display.

In this way, the undefined bit bn is added to the character generator 2'.
By setting a flag to determine whether a character is an undefined character or a defined character, and reading the undefined bits when reading the character generator according to the character code, an undefined code can be detected. Since there is no need to provide a special table for comparison as in the conventional case, the cost of the apparatus is significantly reduced. The example shown is a 5 x 7 dot character used to display alphanumeric characters and kana, whereas in the case of kanji, 15
It consists of ×16 dots, but on the character generator it is 16
It is better to use ×16 bit memory and use the rightmost or leftmost bit as an undefined bit. As shown in the illustrated example, when setting a logic "1" flag to the undefined bit of a defined character, if there is an empty address in the character generator that is not used for character pattern storage, that address is set. Erroneous detection can be prevented by providing an undefined bit and setting a flag of logic "0". Furthermore, even if the display unit is not a display device but a printer capable of producing hard copies, undefined codes can be detected using the same method as in the illustrated example.

As described above, according to the present invention, the character generator 2'
, an undefined bit bn is provided corresponding to each character pattern storage bit bp, and this undefined bit is
A flag indicating whether bn is stored as a character pattern is set, and when reading the character pattern corresponding to the character code, undefined bit bn is set.
By also reading the flag, it is possible to detect whether the input character code is an undefined code. Therefore, there is no need to provide a special table unlike in the past, and it is possible to significantly reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional undefined code detection method, and FIG. 2 is a block diagram showing an embodiment of the undefined code detection method according to the present invention. In the figure, 1 is a control unit, 2 and 2' are character generators, bp is a character pattern storage bit, bn is an undefined bit, 5 is a display, and 8 is a selector.

Claims (1)

[Claims] 1. In a character generator equipped with a storage area for storing character patterns corresponding to character codes, whether or not a character pattern is defined in the surplus storage area of the character pattern storage area. An undefined flag area is provided to indicate whether the character pattern is undefined, and control means is provided to supply the character generator with a code instructing the pattern to be an undefined code when the undefined flag indicates that the character pattern is undefined. , causes the character generator to output a character pattern read from the character generator in response to the undefined flag being set, and causes the character generator to read and output a pattern indicating an undefined code depending on the reset state of the undefined code. An undefined code detection method characterized by: