JPS59191644A - Display control circuit - Google Patents

Abstract

PURPOSE:To aboid the disturbance of dispaly during a rewriting mode by writing the rewrite display data to a display data memory part from a temporary memory part in the timing when a display control part does not read the display data out of the display data memory part. CONSTITUTION:The input data given for rewriting purpose is stored in a main memory 12 and then stored once in a temporary data memory part 4 under the control of a main control part 3. This data gives access to a display data memory part 2 under the control of a display control part 5. Therefore the part 2 receives access from both parts 5 and 3. The access address of the part 2 is switched by an access control part 6. The part 6 connects the output of a display address generating part 13 and the address output sent from the part 3 to the part 2 in terms of time division. Here a control signal controlling part 11 which is set under a normal read mode is changed to a write mode synchronously with the timing when the address output of the part 3 is selected. Thus the contents of the part 2 are rewritten without giving any effect to a display part 1.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] 15 The present invention relates to a display control circuit, and particularly to a display control circuit that makes it possible to eliminate the influence on a display screen when rewriting data stored in a rewritable storage device. This invention relates to a display control circuit.

[Background of the invention] 20
When changing the characters and figures displayed on a display device that displays data stored in a rewritable storage device, it is necessary to rewrite the contents of the storage device (display data storage section) from the main control unit. . In the display control circuit of a conventional display device, control between the main control section and the display control section is asynchronous, and the operation of the main control section has priority over the operation of the display control section. Therefore, when the main control section accesses the display data storage section, it collides with the display control section's access to the display data storage section and the display operation is not affected, for example, display disturbance such as flickering occurs. There was a problem that occurred. - [Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in conventional display control circuits, and to improve the content of the display data storage section. It is an object of the present invention to provide a display control circuit which does not cause display disturbances such as display flickering even during rewriting.

[Summary of the Invention] 2゜The main point of the present invention is that when rewriting the contents of the display data storage section, the input data given for rewriting is once input to the display control circuit under the control of the main control section. The present invention is configured such that the data stored in the temporary storage section is written into the display data storage section when the display control section is not accessing the display data storage section.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. E FIG. 1 is a pull diagram showing the connection configuration of a display control circuit according to an embodiment of the present invention. In the figure, 1 is a display section, 2 is a display data storage section, 3 is a main control section, 4 is a data temporary storage section,
5 is a display control section, d is an access control section, and 7 is a video data generation section. In addition, 8 is a clock generation section;
12 is a main memory.

The data temporary storage section 4 includes an address storage section 9, a data storage section 10, and a write or read control signal control section 1.
The write or read control signal controller 11 is composed of, for example, a flip-flop. The display control section 5 includes a display address generation section 13 and a control signal generation section 14. Further, as shown in FIG. 2, the access control section 6 has a function of periodically switching between the output of the address storage section 9 and the output of the display address generation section 13, and is composed of, for example, a multiplexer. In addition,
In FIG. 1, thin arrows indicate the flow of control signals, and thick arrows indicate the flow of addresses or data. ++1 The operation of this embodiment configured as described above will be explained below.

Characters and figures to be displayed on the display section 1 are obtained by reading data from the display data storage section 2 under the control of the display control section 5 and converting it into video data that can be displayed on the display section 1° in the video data generation section 7. and display it.

When changing the display contents of the display unit 1, as mentioned above,
The contents of the display data storage section 2 will be rewritten, and this process is performed as follows. .

The input data given for rewriting is stored in the main memory.

12, and is temporarily stored in the data temporary storage section 4 under the control of the main control section 3. At this time, the address of the input data is stored in the address storage section 9, and the data is stored in the data storage section 10. - The data stored in the temporary data storage section 4 is accessed from the display data storage section 2 under the control of the display control section 5.

Therefore, the display data storage section 2 is accessed by both the display control section 5 and the main control section 3, but this access switching is performed under the control of the display control section 5, and the display data storage section 2 is accessed by both the display control section 5 and the main control section 3. The access address of section 2 is switched by the access control section 6.

FIG. 2 is a timing chart of the above operation.

In the figure, A is the address data output from the main control unit 3 and stored in the address storage unit 9 of the data temporary storage unit 4, and B is the output of the display address generation unit 13 of the display control unit 5. be. Further, C is an access signal that changes periodically based on the control signal sent from the display control unit 50 control signal generation unit 14 (an input to the control unit 6, and a switching signal when accessing the display data storage unit 2). Yes. And,
D indicates an address signal for accessing the display data storage unit 2 selected by the switching signal C.

As is clear from FIG. 2, the access control section 6 uses the output of the display address generation section 13 of the display control section 5 (the above signal B) and the address output from the data temporary storage section 4, that is, the main control section 3. (the above signal A) is connected to the display data storage section 2 in a time-sharing manner. Here, the control signal control section 11, which is normally in the read mode, is put into the write mode in synchronization with the timing at which the address output from the main control section 3 is selected, thereby controlling the display section l. It is possible to rewrite the contents of the display data storage unit 2 without any influence. The timing at which the address output from the main control unit 3 is selected can be, for example, by using the retrace time of the display screen. Good.

In the above explanation, the main control unit 3 to the display data storage unit 2
Although data rewriting based on control has been described, the same applies to data reading. Data reading by the main control section 5 does not affect the display on the display section 1 by the display control section 5.

〔Effect of the invention〕

As described below, according to the present invention, input data given for rewriting display data is temporarily stored in the data temporary storage section under the control of the main control section, and the display control section rewrites the display data. Since the data is temporarily sent from the storage section to the display data storage section and written (rewritten) or read at a timing when the display data is not being read from the storage section, the display data can be displayed by accessing the display data storage section from the main control section. This has the remarkable effect of realizing a display control circuit that can completely eliminate interference.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation timing chart thereof.・l; Display section, 2
; display data storage unit, 3; main control) control unit, 4: data temporary storage unit, 5: display control unit, 6: access control unit, 7:
Video data generation section, 8: Clock generation section, 9 Near address storage section, 1°: Data storage section, 11: Write or d output control signal control section, 12: Main memory, 13: Display address generation section, 14: Control Signal generator. <Co(J ρ

Claims (1)

[Claims] In a display control circuit having a display control section for reading data in a storage device and displaying it on a display section, and a main control section for controlling writing of data to the storage device or reading of data from the storage device, the above-mentioned A temporary data storage means for temporarily storing input data from the main control section, and an access control means for controlling access from the main control section and access from the display control section to the storage device in a time-sharing manner. Characteristic display control circuit.・