JPH04181990A - Screen display device - Google Patents

Abstract

PURPOSE:To prevent the increase in the burden of an external microcomputer by providing a means for detecting and correcting errors and detecting the error of character information, then correcting the error and outputting the corrected information as correct data. CONSTITUTION:The character information from an input control circuit 1 in an error detecting and correcting circuit 5 is inputted by each one bucket to an error detecting circuit 6 and whether there is the error in the character information A or not is detected by the check code B added to this information in the above-mentioned circuit. The result thereof is stored in a buffer memory 7. The character information is inputted to an error correcting circuit 8 when the error is detected in the character information. The information is corrected to the correct information in accordance with the check code B in this circuit and is then outputted to a RAM 3 for display. The character information is directly transferred to the RAM 3 for display without being passed through the error correcting circuit 8 when there is no error therein. The burden of the external microcomputer 20 is decreased in this way and the higher function and performance of the display functions are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device that displays characters such as letters, numbers, and symbols on a screen in response to character information input from the outside.

[Prior Art] When character information such as letters is transferred from an external microcomputer to a screen display device, errors may occur in the character information due to the influence of external noise during the process of passing through an interface or the like.

Even if an address signal is generated based on character information containing such an error, outputted to the display RAM, and stored, normal screen display will not be possible.

As a countermeasure to this problem, a screen display device as shown in FIG. 5 has been proposed in the past.

FIG. 5 is a block diagram showing a conventional screen display device 10, in which 1 indicates an input control circuit, 2 an error detection circuit, 3 a display RAM, and 4 a character ROM.

The input control circuit 1 inputs a character RO? from an external microcomputer 20 through an interface (not shown) in response to character information among display data such as letters, numbers, symbols, and other sizes, colors, etc. An address signal and the like at I4 are generated and inputted to the error detection circuit 2.

The error detection circuit 2 detects whether or not there is an error in the input character information, and if there is no error, outputs the information to the display RAM 3. The display RAM 3 stores the address signal of the character information input from the input control circuit 1, stores dot pattern data for screen display based on this, and retrieves the dot pattern data from the corresponding address of the character ROM 4. The data is read out and output as a video signal, and characters are displayed on the screen in predetermined display colors, sizes, positions, and other patterns.

On the other hand, when an error is detected, the error detection signal of the error/error detection circuit 2 is output to the external microcomputer 20,
In response to the error detection signal, the microcomputer 20 inputs the display data in which an error has been detected again to the control circuit l.
A configuration is adopted in which so-called refresh is performed.

[Problem to be solved by the invention]

However, providing such an external microcomputer 20 with noise countermeasures as described above poses a problem in that the burden on the microcomputer 20 increases accordingly.

The present invention has been made in view of the above circumstances, and its purpose is to provide an error detection and correction means in place of the error detection circuit, detect errors in character information, correct them, and output them as regular data. The purpose of the present invention is to provide a screen display device that can prevent an increase in the burden on an external microcomputer 20.

[Means for Solving the Problems] The screen display device according to the present invention includes error detection and correction means for detecting and correcting errors in character information input from the outside.

[Effect]

According to the present invention, it is thereby possible to detect errors in character information, correct them, and obtain regular character information without using an external microcomputer.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a block diagram of the apparatus of the present invention, in which IO indicates a screen display device and 20 indicates an external microcomputer. Character information such as letters sent from the microcomputer 20 via an interface (not shown) together with a screen display command is sent to the input control circuit 1.
The input control circuit 1 is designed to generate an address signal corresponding to a character ROM 4 whose character information will be described later, and to output this to an error detection and correction circuit 5.

The character information inputted from the external microcomputer 20 to the error detection and correction circuit 5 via the input control circuit 1 is in a bucket format for each predetermined bit length as shown in FIG.

FIG. 2 is a schematic diagram showing bucket-type data input from an external microcomputer 20, in which a check code B for detecting an error is added to the character information %A.
The configuration has been added.

FIG. 3 is a detailed block diagram of the error detection and correction circuit 5, and FIG. 4 is a flowchart showing the processing procedure in the error detection and correction circuit 5. In the error detection and correction circuit 5, the character information from the input control circuit 1 is input to the error detection circuit 6 packet by packet (step S1), and the check code B added here is used to check whether or not the character information A has an error. In step S2), it is stored in the sofa memory 7.

If an error is detected in the character information, the character information is input to the error correction circuit 8, where it is corrected to regular information based on check code B (step S
3), it is output to the display RAM 3, and if there is no error in the character information, it is directly transferred to the display RAM 3 without going through the error correction circuit 8 (step S4).

The display RAM 3 receives direct input from the input control circuit 1,
Further, the error detection and correction circuit 5 stores the address of the character information corrected to regular data, and based on this, the dot pattern data for screen display read from the corresponding address of the character ROM 4 is output as a video signal. Predetermined color and size.

The position and other patterns are displayed on the display screen.

In the above embodiment, the configuration in which the error detection and correction circuit 5 is arranged between the input control circuit 1 and the display RAM 3 has been described, but the configuration is not limited to this in any way. After detecting and correcting errors in display data from the microcomputer 20,
It may also be input to the input control circuit 1.

〔Effect of the invention〕

As described above, the device of the present invention detects errors contained in character information input from the outside, and if there are errors, corrects them and immediately outputs them as regular data.
The burden on the external microcomputer is reduced, and
High-performance display functions.

The present invention has excellent effects such as improved performance.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the device of the present invention, Fig. 2 is a schematic diagram of bucket-type data transmitted from an external computer,
Figure 3 is a block diagram of the error detection and correction circuit, Figure 4 is a flowchart showing the procedure in the error detection and correction circuit, and Figure 5 is a block diagram of the error detection and correction circuit.
The figure is a block diagram of a conventional device. 1... Input control circuit 3... Display RAM 4.
・Character ROM 5 ・Error detection and correction circuit
6...Error detection circuit 7...Buffer memo υ 8.
. . . Error correction circuit 10 . . . Screen display device 20 . . . Microcomputer In the drawings, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa 1st
Figure 2 Display data from microcomputer
From the figure input control circuit. Figure 3 Input control circuit Figure 4 Figure 5

Claims (1)

[Claims] (1) A screen display device that displays a corresponding character on a screen based on externally input character information, characterized in that it is equipped with error detection and correction means for detecting and correcting errors in character information. Device.