Display control apparatus having replaceable color palette

• US 20020011995A1
• Filed: 03/29/2001
• Published: 01/31/2002
• Est. Priority Date: 03/30/2000
• Status: Active Grant

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Sasaki, Toru
• Granted Patent: US 6,897,873 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

A display control apparatus contains a video memory, a video memory controller, a color palette memory and a color palette replacer signal generator. The video memory stores display data that are read from a CD-ROM and contain header data (HA-HD), palette data (P0-P2) and bitmap data (BA-BD) in connection with four planes which are combined together to form one frame of picture. The header data contain a color palette pointer (CPP) and a color palette replacer instruction (CPP31) with respect to each of the planes. The video memory controller reads the palette data and bitmap data from the video memory in accordance with addresses designated by the header data. The color palette replacer signal generator generates a color palette replacer signal (COL) based on the header data so as to make determination whether to replace contents of color palettes with respect to the planes respectively. If the color palette replacer instruction designates color palette replacement, the video memory controller unconditionally replaces previous palette data with present palette data on the color palette memory. If the color palette replacer instruction does not designate color palette replacement, the video memory controller replaces the previous palette data with the present palette data on the color palette memory only when a present color palette pointer designating the present palette data differs from a previous color palette pointer designating the previous palette data. Thus, it is possible to considerably reduce time for replacement of contents of the color palettes.

Claims

1. A display control apparatus comprising:

a video memory for storing color data, which are used to designate colors for displayed dots, palette data for use in conversion of the color data and address data representing addresses of the color data and the palette data;

a first video memory controller for reading the palette data from the video memory in accordance with the address data, so that read palette data are written to a color palette memory;

a second video memory controller for reading the color data from the video memory in accordance with the address data, so that read color data are subjected to conversion on the color palette memory in accordance with the palette data; and

an output circuit for outputting either the color data read from the video memory or converted color data output from the color palette memory to a display,

wherein if present address data designating present palette data match with previous address data designating previous palette data, the first video memory controller does not write the present palette data to the color palette memory.

2. A display control apparatus according to claim 1 wherein at completion of writing the previous palette data to the color palette memory, the first video memory controller retains the previous address data designating the previous palette data in a register, so that the first video memory controller determines whether to replace content of the color palette memory by comparison between the present address data and the previous address data.

3. A display control apparatus according to claim 1 or 2 wherein the video memory stores a color palette replacer instruction, so that if the color palette replacer instruction designates the color palette replacement, the first video memory controller proceeds to replacement of the content of the color palette memory unconditionally, regardless of the address data.

4. A display control apparatus comprising:

a video memory for storing display data that contain header data, palette data and bitmap data in connection with a plurality of planes which are combined together to form one frame of picture, wherein the header data contain a color palette pointer and a color palette replacer instruction with respect to each of the planes;

a color palette memory for storing color palettes with respect to the plurality of planes;

a video memory controller for reading the palette data and the bitmap data from the video memory in accordance with addresses designated by the header data; and

a color palette replacer signal generator for generating a color palette replacer signal based on the header data so as to make determination whether to replace content of the color palette with respect to each of the planes,

wherein if the color palette replacer instruction designates color palette replacement, the video memory controller unconditionally replaces previous palette data with present palette data on the color palette memory, while if the color palette replacer instruction does not designate color palette replacement, the video memory controller replaces the previous palette data with the present palette data on the color palette memory only when a present color palette pointer designating the present palette data differs from a previous color palette pointer designating the previous palette data.

5. A display control apparatus according to claim 4 wherein the header data contain a bitmap data format representing a format of the bitmap data with respect to each of the planes, so that the bitmap data are converted to RGB color data on the color palette memory in response to the bitmap data format.