JPS6330896A - Display device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a character display device fil (cha
racterdisplay).

[Conventional technology]

Figure 2 is a block diagram showing a conventional device.
i+ is the system bus, (2) is the CRT controller, (
3) is a data transceiver, (4) is a select circuit, (
5) is refresh memory (re'fresh mem
ory ), (6) is the font memory (font m
(7) is a parallel-to-serial conversion circuit (designated as P/S in the drawing), +81 is an oscillator, and (9) is a video control circuit. Also (la), (lb),
c lc) , (2a) , (2b) , (2c
), (2d), (4a), (5a).

(6a), (7a), (8a), (10a)) are the signals, respectively, (1a) is the CPU address, (1b) is the data, (IC) is the command signal, (2a) is the CRT address, (2b) ) is a memory control signal, '(2c) is a raster address, (2d) is a video control signal, (4a)
is the memory address, (5a) is the character code, (6
a) is the font pattern, (7a) is the serial data, (
8a) is a clock, and (10a) is a video signal.

Since the operation of the character display device shown in FIG. 2 is well known, a general explanation thereof will be omitted.
Only the parts directly related to this invention will be explained.

In the refresh memory (5), character codes are stored and arranged at address positions corresponding to the display positions where the characters represented by the codes are displayed on the display screen, and this refresh memo January 5) The contents can be changed freely. That is, when attempting to replace a character code stored at an address location with a new character code, the CPU (not shown) transfers the CPU address (1a) and character code data ( 1b). In this case, the select circuit 4) outputs the CPU address (1a) as the memory address (4a), and the system bus (4a) outputs the CPU address (1a) as the memory address (4a).
New character code data transmitted from 1) (
1b) is added to the refresh memory (5) via the data transceiver (3), so it is added to the location specified by the CPU address (1a) at the timing when the CRT controller (2) outputs the memory control signal (2b). Data (1b) is written.

On the other hand, the font memory (6) is configured not to be rewritten, and is read out using the character code (5a) and raster address (2C) read out from the refresh memory (5) as addresses. It is used as a read-only memory and is often made up of memory elements that are not writable or that require a special writing device, such as EEPROM.

[Problem that the invention seeks to solve]

As described above, the conventional device does not allow the user to change the contents of the font memory, but this imposes various inconvenient restrictions on the use of the character display device. For example, a user may want to display a specific character in a unique font, and for that specific purpose, the user may want to erase font patterns that are never used in the font memory and create a special font pattern for that purpose. Sometimes you may want to replace it with the font pattern used in the font pattern.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a character display device that allows a user to change the contents of a font memory.

[Means for solving problems]

In the display device of the present invention, the font memory is constituted by a writable memory element, and a font pattern register temporarily stores a font pattern to be written in the font memory, and an address signal is used to write the contents of the font pattern register. A character code register for temporarily storing a character code is provided, and the contents of the font pattern register are written to a position in the font memory whose address is the contents of the character code register during the retrace period of scanning the display screen.

[Effect]

The process of inputting data from the CPU to the character code register and font pattern register can be executed regardless of reading the refresh memory, reading the font memory, and displaying the font pattern.
Furthermore, since the font memory is rewritten during the retrace period of raster scanning, the font memory can be rewritten without disturbing the displayed image.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.
In the figure, the same symbols as in FIG. 2 indicate the same parts or the same signals, (11) is the data select circuit, (12) is the code select circuit, (13) is the command decoder, and (14) is the code select circuit.
) is the character code register, (15) is the font pattern register, (2e) is the retrace signal, (lla) is the font pattern input data, (12a) is the font address, (13a) is the conversion control command, (60) is This is writable font memory.

The writable font memo IJ (60) is typically comprised of volatile memory elements and is therefore lost when power to the circuit shown in FIG. 1 is cut off. Therefore, the contents of the font memo IJ (60) should be stored in an auxiliary storage device made up of a non-volatile record carrier and loaded from the auxiliary storage device into the font memory (60) at the time of initialization. However, since this operation is similar to the operation of loading data from the auxiliary storage device to the main storage device in a general magnetic computer, a detailed explanation will be omitted.

Once the loading into the font memo IJ (60) at the time of initialization is completed, the font memo IJ (60) becomes similar to the font memory (6) in Figure 2, which was possible with the circuit in Figure 2. All operations are also possible for the circuit shown in Figure 1. In addition, the circuit shown in Figure 1 also uses the font memory (6o
) can be rewritten.

When changing the contents of font memo IJ (60)C
The PU sends out a conversion command as a command signal (1c) on the system bus (1). This conversion command is decoded by a command decoder (13) and output as a conversion control command (13a), which then passes through the character code register (14), code select circuit (12), font pattern register (15), and data select circuit (11).
control. The CPU then sends the character code to be input to the character code register (14) and the hex7 ont pattern to be input to the font pattern register (15) as data (1b) on the system bus (1). Since the total number of bits in the font pattern is large, the portion corresponding to each test 1 of the entire font pattern may be sent as one piece of data (1b).

The character code register (14) and font pattern register (15) controlled by the conversion control command (13a) store the character code and 7-onto pattern sent from the system bus (1).

The code select circuit (12), which is controlled by the conversion control command (13a) and knows the predetermined timing during the retrace period from the retrace signal (2e), selects the input from the character code register (14) and selects the font. Output as address (12a) and data select circuit (11)
selects the input from the font pattern register (15) and outputs it as font pattern input data (lla). The font pattern input data (lla) is written to the font memo IJ (6(J)) at the address position indicated by the font address (12a).

Note that the circuit configuration in Figure 1 includes Font Memo IJ (60
) is also included for the CPU to initially adjust the contents of. In this case, the code select circuit (12) and data select circuit (11) are configured so that the CPU address (1a) sent from the CPU becomes the font address (12a), and the data (1b) becomes the font pattern input data (lla). A selection is made.

After the font memory (60) has been rewritten as described above, when the same character code that was set in the character code register (14) is read from the refresh memory (5), the font pattern register The same dot-bang characters as the font pattern set in (15) are displayed.

In the above embodiment, the content of the font memo IJ (60) was explained as being rewritten character by character, but the character code register (14) and font pattern register (
By increasing the capacity of 15), it is possible to rewrite multiple characters at once.

〔Effect of the invention〕

As described above, according to the present invention, since the user can rewrite the contents of the font memory, the degree of freedom in using the character display device is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional device. (1) is the system bus, (2) is the CRT controller,
(5) is refresh memory, (60) is font memory, (11) is data select circuit, (12) is code select circuit, (13) is command decoder, (14)
is a character code register, and (15) is a font pattern register. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A refresh memory in which each character code indicating each character to be displayed is arranged and stored at an address position corresponding to each character display position on the display screen is scanned on the display screen. The dot pattern representing the shape of the character is read out in synchronization with each read character code as an address from the font memory in which the dot pattern representing the shape of the character is stored as the font pattern, and is read out in synchronization with the raster scan of the display screen, corresponding to the raster position. A display device that sequentially reads portions of a font pattern and displays them on the display screen, the font memory comprising a writable memory element, a command decoder for decoding an instruction signal instructing writing to the font memory, and the font described above. A font pattern register that temporarily stores the font pattern to be written to the memory, a character code register that temporarily stores the character code corresponding to the font pattern stored in this font pattern register, and a system bus that transmits according to the output signal of the above command decoder. means for inputting the font pattern and character code to the font pattern register and character code register, respectively; during the retrace period of scanning the display screen, inputting the contents of the font pattern register using the contents of the character code register as an address; A display device comprising: means for writing into a font memory.