JPS6275485A - Display unit - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a raster scan type display device, and more particularly to an improvement for eliminating waste of refresh memory.

[Prior Art] In a CRT display device, display data is stored in a refresh memory corresponding to the screen, and the display data is repeatedly read out from the refresh memory in synchronization with the raster scan of the screen and displayed. .

Now, LSIs (CRT controllers) for controlling the readout of display data are commercially available. This CRT controller outputs a refresh address signal for accessing the refresh memory. This refresh address signal consists of a character address signal and a raster address signal. In the case of a standard CRT controller, the refresh address signal is 16 bits, of which the upper 12 bits are a character address signal and the lower 4 bits are a raster address signal.

In a conventional CRT display device, a refresh address signal output from such a CRT controller is directly supplied to a refresh memory, and the refresh memory is accessed.

[Problems to be Solved] With such a configuration, there is a problem that depending on the number of rasters used for character display, there is a large amount of unused space in the refresh memory, resulting in poor utilization efficiency of the refresh memory.

For example, if the raster address signal is 4 bits and the number of rasters used to display a character is 10, 16 bytes of the refresh memory are allocated to one character as shown in FIG. Even if the value of the raster address signal is only changed from 0 to 9 on the CRT controller side, 16 bytes will be occupied by that character and cannot be used for other characters. The latter 6 bytes are completely wasted.

[Object of the Invention] It is an object of the present invention to provide a raster scan type display device that eliminates the waste of refresh and flash memory as described above and improves its utilization efficiency.

[Means for solving the problem] In order to achieve this object, the present invention inserts an address conversion means into the address circuit of the refresh memory, and performs a specific conversion process on the input address signal. is applied to the refresh memory, so that when the input address signal is applied to the refresh memory as is, the maximum number of rasters determined by the number of bits of the raster address signal in the input address signal is actually used for display. Some characters are allocated to an unused area on the refresh memory that occurs due to the difference in the number of rasters.

[Operation] For example, when an input address signal including a 4-bit raster address signal is directly applied to the refresh memory, 6 bytes per character are wasted as shown in FIG.

According to the present invention, some characters are allocated to such an unused area of the refresh memory by the conversion process of the input address signal by the address conversion means, thereby achieving effective use of the refresh memory.

[Embodiment] An embodiment of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a raster scan type CR according to the present invention.
FIG. 2 is a schematic block diagram for explaining the configuration of main parts of the T display device. In this figure, 22 is a CRT monitor unit; 24 is a refresh memory for storing dot information to be displayed on the screen of the CRT monitor unit 22;
6 is a parallel/serial converter that converts dot information output in parallel from the refresh memory 24 into a serial video signal.

28 is a commercially available standard CRT controller (LSI) which outputs a 16-bit refresh address signal consisting of a 12-bit character address signal and a 4-bit raster address signal. This refresh address signal is input to a multiplexer 30 for address switching. The multiplexer 30 also includes a 16-bit address bus 3 of an external microprocessor 32.
4 is connected. Data transfer between the microprocessor 32 and the refresh memory 24 is performed by a so-called cycle steal method, in which the address signal on the address bus 34 is selected by the multiplexer 30 only during the transfer period, and the refresh address signal is selected during the other periods. is selected by multiplexer 30 and taken into the address circuit of refresh memory 24.

Now, conventionally, the input address signal fetched by the multiplexer 30 is directly sent to the refresh memory 24.
address input.

On the other hand, according to the present invention, the refresh memory 2
An address converter 36 is inserted in the address circuit No. 4. This address converter 36 is composed of, for example, a ROM. The 16-bit input address signal (refresh address signal or signal S'f of the address bus 34) taken in by the multiplexer 30 is subjected to specific address conversion processing by the address conversion Z438, and the converted 16-bit address signal is is applied to the address input of refresh memory 24.

Here, address conversion processing by the address converter 36 will be specifically explained.

The character shall be displayed with 10 rasters,
It is assumed that one byte of dot information is stored in the refresh memory 24 for each raster. The value of the 4-bit raster address signal of the CRT controller 28 is 0.
It is preset to vary within the range of ~9. In this case, if address conversion processing is not performed, the refresh memory 241 contains one character per character as shown in FIG.
Six bytes are allocated, but the latter six bytes are not actually used to display the character and are wasted.

Therefore, in the address converter 36, up to the upper 12 bits of the input address signal, that is, the value of the character address signal (corresponding to the character number), up to a certain value M,
Outputs the input address signal as is. That is, up to the character number M, the input address signal is supplied to the refresh memory 24 as is. Therefore, for each character numbered 0 to M, there are 6 unused bytes, as shown in FIG. 2.

For each character from (M+1) to N (final character number), the character address signal of the input address signal and An address signal obtained by converting the raster address signal is output from the address converter 36. for example,
Address conversion is performed so that the unused 6 bytes of the 0th character and the 4 unused bytes of the 1st character are assigned to the (M+1)th character. CM+
2) Address conversion is performed so that the unused 2 bytes of the 1st character, the 6 unused bytes of the 2nd character, and the 2 unused bytes of the 3rd character are assigned to the character No. 2).

(Thus, the waste of the refresh memory 24 as in the conventional case is eliminated.Considering that in the past, unused bytes of 6 characters were generated for every 10 characters, this invention improves the utilization efficiency of the refresh memory 24. Improve dramatically.

However, the address translation algorithm listed here is boring (
It goes without saying that the above is just an example and can be modified as appropriate.

For example, for every 10 characters, there are 6 unused bytes, so all characters are divided into blocks of 16 characters each, and the lowest numbered 10
There is virtually no address translation for characters,
It is also possible to perform address translation to allocate the unused 60 bytes for the 10 characters to the remaining 6 characters.

Note that there also exists a mechanism for loading data into the refresh memory 24 from the microprocessor 32 side, a timing control mechanism for the refresh memory 24, etc., but since these may be the same as conventional ones, their explanation will be omitted.

Further, the present invention is not limited to CRT display devices.
The present invention can also be applied to a raster scan type display device using a similar refresh memory.

[Effects of the Invention] As explained above, according to the present invention, the address conversion means is inserted into the address circuit of the refresh memory,
The input address signal is given to the refresh memory after being subjected to a specific conversion process by this address conversion means, so that when the input address signal is given to the refresh memory as is, the input address signal is Some characters may be stored in the unused area of the refresh memory 1 unit, which occurs due to the difference between the maximum number of rasters determined by the number of bits of the raster address signal in the signal and the number of rasters actually used for display. 11
Therefore, it is possible to eliminate unused addresses in the refresh memory, thereby achieving the effect of greatly improving the efficiency of its use.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram for explaining the main structure of a CRT display device according to the present invention, and FIG. 2 is an explanatory diagram of an unused area per character. 22.-CRT monitor unit, 24.. Refresh memory, 28.. CRT controller, 36..
Address converter.

Claims (1)

[Claims] (1) In a raster scan type display device, an address conversion means is inserted into the address circuit of the refresh memory, and the input address signal is subjected to a specific conversion process by the address conversion means before being applied to the refresh memory. is related to the difference between the maximum number of rasters determined by the number of bits of the raster address signal in the input address signal and the number of rasters actually used for display when the input address signal is applied as is to the refresh memory. A display device characterized in that some characters are allocated to an unused area on the refresh memory that is generated by the refresh memory.