JPH0715623B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention obtains a character pattern corresponding to each character code by periodically reading out the character code stored in a refresh memory and supplying the character code to a character generator. More particularly, the present invention relates to a display device using a rewritable character generator.

[Conventional technology]

This type of display device has a read-only character generator and a rewritable character generator. In the read-only character generator, standard characters such as JIS first level character patterns are written. Characters in this range are displayed on the CRT display if a character code, that is, a code for the read-only character generator, is written in the display refresh memory. However, since characters within these ranges are generally insufficient, a rewritable character generator is provided, a character pattern is read from a file device or the like, and the character pattern is loaded and displayed. This is called external character processing.

The rewritable character generator has hundreds of characters. A physical series of address numbers is assigned to each character, and this address can be specified to write / read a character pattern that is not in the read-only character generator. Therefore, in order to display this character pattern, it is necessary to write the address number (rewritable character generator code) of the rewritable character generator into the refresh memory.

In a series of character input operations, if the number of characters displayed using the rewritable character generator is less than or equal to the number of characters that can be stored in the rewritable character generator, give a fixed character generator (CG) code to each character. You can Therefore, the rewritable CG can be accessed in the same manner as the read-only CG by writing the CG code in the refresh memory. However, if the number of characters displayed using rewritable CG exceeds the number of characters that can be stored, it cannot be displayed by this method.

Therefore, the original character code is written in the refresh memory, and when the display control circuit detects a character code that requires access to this rewritable CG at the time of refresh, it displays an external character mark and interrupts the software. I am trying. The software learns from this interrupt that it is necessary to display a character that is not in the read-only character generator, reads the character pattern of that character from an external file device, stores it in a rewritable CG, and refreshes the address of that character generator. The method of rewriting to the memory was taken.

[Problems to be solved by the invention]

That is, a conventional device of this type stores a character code in a shared refresh memory, detects a character code corresponding to an external character from the stored character codes, and generates an interrupt, and a refresh memory of the code. The address in the memory is stored and the character pattern corresponding to that character code is indexed and stored in the rewritable CG, and the address of the rewritable CG is rewritten to the corresponding address in the refresh memory instead of the character code. It required a complicated processing circuit. Therefore, the processing circuit becomes expensive and the processing procedure becomes complicated.

Therefore, an object of the present invention is to realize the external character processing of the display device with a relatively simple processing circuit and reduce the cost of the display device.

[Means for solving problems]

The display device of the present invention includes a refresh memory that stores a character code of a character to be displayed, a read-only character generator that stores a character pattern corresponding to the character code of a predetermined character, and a character other than the predetermined character. A rewritable character generator that stores a character pattern corresponding to the character code of the external character, and an external character display request table that stores the address on the refresh memory corresponding to the external character and the character code of the external character to be displayed. And a character generator management table that stores a character code corresponding to the character pattern stored in the rewritable character generator and a flag indicating whether the character code is used in the refresh memory. And the address in the refresh memory and the character code of the external character to be displayed in the order written from the external character display request table, and the character code of the external character to be displayed is already stored in the character generator management table. If the character code of the external character is already stored and the corresponding address on the refresh memory remains the special code indicating the external character, the special code is already stored in the rewritable character generator. If the character code of the external character is not stored, the character pattern is read from the external file device, written in the rewritable character generator, and then the character generator management table is updated. A processing unit, a first process of determining whether or not a character pattern corresponding to a character code of a character to be displayed is stored in the read-only character generator, and a determination of being stored in the first process If it is determined that the character code corresponding to the character pattern of the read-only character generator is written in the refresh memory, and if it is determined that the character code is not stored in the first process, the external character is displayed in the refresh memory. A display processing unit that writes the special code, writes the corresponding address on the refresh memory and the character code of the external character to be displayed in the external character display request table, and performs a third process of activating the external character processing unit. Is equipped with.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings showing an embodiment of the present invention.

In FIG. 1, the display processing unit 1 receives a display request and a character code, and if the character code is a character accommodated in the read-only character generator 7, after converting it to a CG code on the read-only character generator 7. Write to refresh memory 5. When the character code is not stored, a special code indicating an external character is written in the refresh memory 5, the address of the corresponding refresh memory and the character code are registered in the external character display request table 2, and the external character processing unit 3 If is not started, start it. However, if the external character display request table 2 is full,
Wait until this is empty. This operation is shown as a flowchart in FIG.

The external character display request table 2 is a first-in first-out type buffer and has a plurality of entry areas as shown in FIG.
The address RA of the refresh memory and the character code CC are stored.

The character generator (CG) management table 4 is the third
As shown in the figure, the rewritable character generator 6 has as many entry areas as the accommodable characters, and each entry corresponds to each character stored in the rewritable character generator 6. In the character code area CC ′ of the CG management table 4, the character code of the character pattern stored in the rewritable character generator 6 is written.
Further, the status flag SF has a flag PF indicating whether or not the character code is stored in the entry and a flag UF indicating whether or not the character code is being used in the refresh memory 5.

As shown in FIG. 5, the external character processing unit 3 fetches one entry at a time from the external character display request table 2 and sets its character code CC.
Is checked in the CG management table 4. If the character code is already registered, the address (CG code) of the rewritable CG6 corresponding to the entry position of the character code is written in the refresh memory 5 indicated by the address RA.

If the character code is not registered, an empty entry in the CG management table 4 is searched first, and the character pattern read from the external file device 9 is stored in the rewritable CG area corresponding to the empty entry. Also, in order to clarify the storage address position in rewritable CG6, area C of the corresponding entry
This character code is stored in C'and rewritable at the corresponding address of refresh memory 5 Storage address to CG6 (C
Write G code).

When there are no empty entries in the CG management table 4, that is, when all the rewritable character generators 6 are used, the contents in the rewritable character generator 6 are checked by sequentially checking the stored contents in the refresh memory 5. An empty entry is created by searching for an unused pattern and deleting the corresponding entry in the CG management table 4. That is, when searching for an unused entry in the rewritable character generator 6, the flag UF indicating whether the CG management table 4 is in use is turned off, and then the refresh memory 5 is used.
Are sequentially read, and the UF flag of only the entry corresponding to the used CG code is turned on. When the reading of the refresh memory 5 is completed, the entry whose UF flag is off is not used and is used as an empty entry.

As described above, since the rewriting is not performed until all the areas of the rewritable CG6 are used, each time the refresh memory 5 is rewritten, it is detected whether or not the character pattern stored in the rewritable CG6 is necessary. There is no need to do so, and the processing speed can be improved.

When the external character processing unit 3 is requested to display the characters already registered in the CG management table 4, the external character processing unit 3 converts the CG code in the rewritable character generator 6 and writes it in the refresh memory 5, as described above. It was However, also in this case, if the corresponding position of the refresh memory 5 is not a special code indicating an external character, the refresh memory 5
Do not write the CG code. This is because there is a possibility that the next display request is generated at that position during the period when the character code of the external character is registered in the external character display request table 2, and the display of a new character is requested.

The display unit 8 periodically reads out the refresh memory 5, reads a character pattern from a corresponding position of the read-only character generator 7 or the rewritable character generator 6 according to a code stored therein, and reads the character pattern.
Display on the display.

〔The invention's effect〕

As described above, according to the present invention, the external character processing in the display device can be realized with a simple configuration by performing the writing control of the external character generator by referring to the CG management table.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of an external character display request table, FIG. 3 is a block diagram of a CG management table, and FIG. 4 is an operation flowchart of a display processing unit. FIG. 5 is an operation flowchart of the external character processing unit. 1 ... Display processing unit, 2 ... External character display request table, 3 ...
... External character processing unit, 4 ... CG management table, 5 ... Refresh memory, 6 ... Rewritable character generator,
7 ... Read-only character generator, 8 ... Display section.

Continuation of the front page (56) Reference JP-A-56-52481 (JP, A) JP-A-57-161781 (JP, A) JP-A-56-42272 (JP, A) JP-A-57-129487 (JP , A) JP-A-58-166441 (JP, A) JP-A-59-99485 (JP, A)

Claims (1)

[Claims] 1. A refresh memory for storing a character code of a character to be displayed, a read-only character generator for storing a character pattern corresponding to the character code of a predetermined character, and an external character other than the predetermined character. A rewritable character generator that stores a character pattern corresponding to the character code, an external character display request table that stores an address on the refresh memory corresponding to the external character and a character code of the external character to be displayed, A character generator management table storing a character code corresponding to a character pattern stored in the rewritable character generator and a flag indicating whether or not the character code is used in the refresh memory; The address on the refresh memory and the character code of the external character to be displayed are retrieved from the character display request table in the order written, and it is determined whether the character code of the external character to be displayed is already stored in the character generator management table. However, if the character code of the external character is already stored and the corresponding address on the refresh memory remains the special code indicating the external character, the special code is already stored in the rewritable character generator. If the character code of the external character is not stored, the external character processing unit that reads the character pattern from the external file device, writes the character pattern in the rewritable character generator, and then updates the character generator management table. A first process for determining whether or not a character pattern corresponding to a character code of a character is stored in the read-only character generator; and, if it is determined to be stored in the first process, in the refresh memory. Writing a character code corresponding to the character pattern of the read-only character generator;
And the special code indicating the external character is written in the refresh memory and the corresponding address on the refresh memory and the character code of the external character to be displayed are displayed in the refresh memory. A display device, comprising: a display processing unit that writes in the external character display request table and performs a third process of activating the external character processing unit.