JPH03154580A - On-screen display circuit - Google Patents

Abstract

PURPOSE:To attain complicated display with a simple program by providing a microcomputer, a display control section and a read only memory. CONSTITUTION:A display control section 2 reads a program corresponding to a program number from a read only memory 3 when a program number inputted from a microcomputer 1 is received and the display position of the information displayed by the program is designated. Then the display control section 2 reads the display data indicating a memory address storing a pattern data corresponding to the display position from the read only memory 3 and the pattern data of a graph to be displayed according to the content of the display data is read from the read only memory 3 and displayed on a screen of the display device 4. Thus, the microcomputer 1 attains a complicated display with a simple program.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an on-screen display circuit that displays channel and volume information on-screen on a CRT screen of a television receiver or the like.

(b) Prior Art Conventionally, a display circuit generally called an on-screen display IC is used in television (TV) receivers, video tape recorders, etc. to display channels and volume.

This on-screen display IC has an internal character generator and is used in combination with a microcomputer to display characters, symbols, etc. on the TV screen according to commands from the microcomputer. By the way, since this type of IC is designed based on characters, there are restrictions on the type of character information that can be displayed, the display position, the color, etc.

In addition, if you want to display not only characters but also graphic figures colored in multiple colors in small units at arbitrary positions on the CR7 screen, use an image memory that corresponds pixel by pixel to the screen to be displayed. There is a method in which a microcomputer writes a graphic pattern to be displayed into the image memory.

(C) Problems to be Solved by the Invention By the way, when on-screen display is performed using an on-screen display IC, character display is the basis, so the type of character information displayed is mostly text. , there are restrictions such as the coloring unit being two colors within one character, and the display position being a grid-shaped character unit that divides the screen by the size of the character, and displaying graphic figures expressed in multiple colors in small units. A problem arises when attempting to display small changes in the display, for example, when a display figure moves little by little over time.

On the other hand, if an image memory is used, display can be performed freely, but an image memory corresponding to the screen and a memory control circuit to control this memory are required.

Furthermore, in both of the above methods, the selection, position, display color, etc. of characters to be displayed must be specified each time by a microcomputer program. For this reason, in order to perform a complicated display, for example, a display in which a displayed figure moves while changing little by little over time, time management and display changes must all be performed by a microcomputer program.

Generally, a microcomputer for on-screen display in a VTR, TV receiver, etc. also has the function of controlling channel selection, so if the load on the display program increases, a microcomputer dedicated to on-screen display must be prepared. Furthermore, if any changes to the display contents are required, the microcomputer program itself must be changed (and the on-screen display IC may also have to be changed in some cases).

Therefore, the present invention aims to solve the above-mentioned problems and provide an on-screen display circuit that can perform complex display with a simple circuit configuration.

(d) Means for Solving the Problems The present invention solves the above problems in a display circuit that superimposes a signal representing character information such as letters and figures on a video signal and displays it on the screen of a display device. The display control section is equipped with a microcomputer, a display control section, and a read-only memory, and when the display control section receives a program number inputted from the microcomputer, it reads a program corresponding to the program number from the read-only memory, and reads the program corresponding to the program number from the read-only memory. A display position of information to be displayed is specified by a program, and then the display control unit reads display data from the read-only memory that indicates a memory address in which pattern data corresponding to the display position is stored;
Further, pattern data of a figure to be displayed is read from the read-only memory and displayed on the screen of the display device according to the contents of the display data.

(e) Operation If configured as described above, the microcontroller can perform complex displays with an extremely simple program. Furthermore, by simply changing the contents of the read-only memory, the display contents can be changed without changing the microcomputer program.

(F) Embodiments Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

Fig. 1 shows a schematic block diagram of the on-screen display circuit of the present invention. The control unit (2) first reads the program corresponding to the program number from the read-only memory (3). i.e. read-only memory (ROM) (3)
Inside, there are multiple programs to control the display format in advance, display data that indicates the memory address where pattern data corresponding to the display position specified by these programs is stored, and pattern data for the figures to be displayed. Stored.

In accordance with the program read from the read-only memory (3), the display control unit (2) sets the display window determined by the display start position and display width on the screen of the CRT (4), and sets the display data on the read-only memory (3). Set memory address. Next, the display data is read from the read-only memory (3) to the display control unit (2), and then the pattern data of the memory address represented by the content of the display data is read from the read-only memory (3) and the D/A It is output to the conversion circuit (5).

The D/A conversion circuit (5) converts the digital data output from the display control section (2) into an analog signal and outputs it to the display switching circuit (6). This display switching circuit (6) switches between the television video signal and the analog character information signal output from the D/A conversion circuit (5) using the switching signal (S) output from the display control section (2). C
It is displayed on RT(4).

FIG. 2 is a block diagram showing a more detailed configuration of the display control unit (2) shown in FIG. 1, and FIG. 3 explains the transmission and reception of signals between each block in FIG. 1 and its operation. Next, the operation of the display control section (2) in FIG. 2 will be explained in detail with reference to FIG. 3.

Microcomputer (program number is displayed from 1 to control unit (2)
When the command is output to the program, the data of that program number is first input to the microcomputer interface circuit (7), which determines whether the command is auxiliary data (the auxiliary data will be described later) and the address generation circuit (13). ) generates a memory address in the read-only memory (3) where the program corresponding to the program number is stored. The generated memory address passes through the read-only memory interface circuit (14) and reads out the program corresponding to the program number from the read-only memory (3). The program read out by the read-only memory (3) passes through the read-only memory interface circuit (14) again, and then passes through the internal bus (15) to the window generation circuit (9) and the display control circuit (10).
, is input to the address generation circuit (13). In the window generation circuit (9), a display window determined by the vertical and horizontal display start positions and display width is set by this program. In the display control circuit (10), various flags related to display are set by the above program.

Further, in the address generation circuit (13), the memory address of display data to be read next is set by the program. The above processing is performed during the vertical retrace period, which is outside the display period on the CRT display section (4).

When the CRT display section (4) reaches a valid display period, horizontal and vertical synchronization signals are counted in the window generation circuit (9) and compared with the previously set display window position, and if they match, the display data is addressed. Generation circuit (13)
Read-only memory (
Read from 3). This read display data is transmitted to the address generation circuit (13), thereby setting the memory address of the pattern data to be read next. When the pattern data is read from the read-only memory (3) at the memory address set in this way, the display control circuit (10) becomes data representing R, G, and B signals, and the display data interface circuit (12) receives the pattern data. The signal is then output to the D/A converter (5).

The above processing is repeated within the display window range within the effective display period, and a predetermined display is performed. Note that a display time is also set in the display control circuit (10) by the program, and the display is repeated within this set time.

Although not shown in Fig. 3, for example, when displaying channels, the microcomputer (
1) must be supplied to the display control unit (2). This auxiliary data is temporarily held in the microcomputer interface circuit (7), supplied to the address generation circuit (13) when reading the pattern data, and added as an offset address to the memory address of the pattern data.

In Fig. 2, the timing clock used in each circuit block is generated by a timing generation circuit (11) to which horizontal and vertical synchronization signals (■,) (V,) are input, and is supplied to each block. The arithmetic processing circuit (8) performs arithmetic processing such as data comparison, addition, and subtraction.

Fig. 4 shows a conceptual diagram showing the relationship between display data, pattern data, and CRT display. One piece of data exists for each character block. Further, the display width of the display window is set for display data in character block units. In a CRT display, screen scanning is performed, and in the same way, addresses are counted horizontally and vertically for display data and enter the display area, that is, when the address of display data matches the display window,
The pattern data is read out at the memory address indicated by the content of the display data and displayed on the CRT.

(g) Effects of the Invention As described above, according to the present invention, a microcomputer can perform complex display with an extremely simple program.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing one embodiment of the on-screen display circuit of the present invention, FIG. 2 is a detailed block diagram of a display control section used therein, and FIG. 3 is a block diagram of the on-screen display circuit of the present invention. The operation explanatory diagram, FIG. 4, is a conceptual diagram showing the relationship between display data, pattern data, and CRT display. (1)...Microcomputer, (2)...Display control unit, (3)...Read-only memory.

Claims (1)

[Claims] (1) A display circuit that superimposes a signal representing character information such as letters and figures on a video signal and displays it on the screen of a display device, comprising a microcomputer, a display control unit, and a read-only memory, When the display control unit receives a program number input from the microcomputer, it reads a program corresponding to the program number from the read-only memory;
A display position of information to be displayed is specified by the program, and then the display control section reads display data indicating a memory address in which pattern data corresponding to the display position is stored from the read-only memory, and further controls the display. An on-screen display circuit configured to read pattern data of a figure to be displayed from the read-only memory according to the contents of the data and display it on the screen of the display device.