Display controller for display apparatus

• US 6,734,863 B1
• Filed: 03/30/2000
• Issued: 05/11/2004
• Est. Priority Date: 03/31/1999
• Status: Expired due to Term

• Current Assignee: HTC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ikeda, Takashi
• Primary Examiner(s): Chauhan, Ulka J.
• Application Number:
  US09/538,985
• Time in Patent Office: 1,503 Days
• Field of Search: 345/503, 345/520, 345/531, 345/535, 345/545, 345/556, 345/561
• US Class Current: 345/531
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 5/001 Arbitration of resources in a display system, e.g. control of access to frame buffer by video controller and/or main processor

Abstract

A display controller for a display apparatus having a memory function which can reduce power consumption efficiently is disclosed. A rewriting comparison circuit detects whether or not rewriting of different data by a graphic engine since the last display updating by a reflect control circuit, and stores resulting information into a TagRAM. The refresh control circuit checks the address of the TagRAM prior to the updating of the display and, only when the data at a corresponding address of a VRAM has been rewritten since the last display updating, the refresh control circuit performs reading in of the data from the VRAM and signaling of the data to the display apparatus having a memory function.

Claims

1. A display controller for controlling a display apparatus having a memory function, comprising:

display updating means for updating a display of said display apparatus;

display data storage means;

display data production means for producing and writing display data into said display data storage means;

rewriting comparison means for detecting by comparison whether or not rewriting of data in a line, which is a set of pixels including a certain number of successive pixels on one scanning line of said display apparatus and is used as a unit of comparison, into said display data storage means has occurred;

rewriting information storage means for storing comparison information of a result of the comparison of said rewriting comparison means into a corresponding address thereof;

rewriting control means for checking, prior to updating of the display by said display updating means, the address of said rewriting information storage means and, only when stored contents of the address represent rewriting of different data, reading the data from said display data storage means and signaling the data to said display apparatus through said display updating means; and

line size variation means for varying the number of pixels which form a line as the unit of rewriting comparison,

wherein the line size variation means varies the number of pixels which form a line at a time point between two adjacent refresh cycles of the display.

2. A display controller as claimed in claim 1, wherein said display data storage means includes said rewriting comparison means for detecting by comparison whether or not rewriting to different data has occurred.

3. A display controller as claimed in claim 2, wherein said rewriting comparison means latches and compares potentials to detect whether or not rewriting to different data has occurred.

4. A display controller as claimed in claim 3, further comprising arbitration means for arbitrating accessing to said display data storage means from said rewriting comparison means and from said rewriting control means and for arbitrating accessing to said rewriting information storage means from said rewriting comparison means and said rewriting control means.

5. A display controller as claimed in claim 2, further comprising arbitration means for arbitrating accessing to said display data storage means from said rewriting comparison means and from said rewriting control means and for arbitrating accessing to said rewriting information storage means from said rewriting comparison means and said rewriting control means.

6. A display controller as claimed in claim 1, further comprising arbitration means for arbitrating accessing to said display data storage means from said rewriting comparison means and from said rewriting control means and for arbitrating accessing to said rewriting information storage means from said rewriting comparison means and said rewriting control means.

7. A display controller as claimed in claim, 1, wherein the number of pixels which form a line is changed based on one of:

a) hardware, and b) a software instruction provided to the display data storage means.

8. A display controller for controlling a display apparatus having a memory function, comprising:

display updating means for updating a display of said display apparatus;

display data storage means;

display data production means for producing and writing display data into said display data storage means;

rewriting comparison means for detecting by comparison whether or not rewriting of data in a line, which is a set of pixels including a certain number of successive pixels on one scanning line of said display apparatus and is used as a unit of comparison, into said display data storage means has occurred;

rewriting information storage means for storing comparison information of a result of the comparison of said rewriting comparison means into a corresponding address thereof;

rewriting control means for checking, prior to updating of the display by said display updating means, the address of said rewriting information storage means and, only when stored contents of the address represent rewriting of different data, reading the data from said display data storage means and signaling the data to said display apparatus through said display updating means;

arbitration means for arbitrating accessing to said display data storage means from said rewriting comparison means and from said rewriting control means and for arbitrating accessing to said rewriting information storage means from said rewriting comparison means and said rewriting control means; and

line size variation means for varying the number of pixels which form a line as the unit of rewriting comparison,

wherein said display data storage means includes said rewriting comparison means for detecting by comparison whether or not rewriting to different data has occurred,

wherein said rewriting comparison means latches and compares potentials to detect whether or not rewriting to different data has occurred, and

wherein the line size variation means varies the number of pixels which form a line at a time point between two adjacent refresh cycles of the display.

9. A display controller as claimed in claim, 8, wherein the number of pixels which form a line is changed based on one of:

a) hardware, and b) a software instruction provided to the display data storage means.