Information
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Patent Grant
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6400361
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Patent Number
6,400,361
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Date Filed
Thursday, April 23, 199826 years ago
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Date Issued
Tuesday, June 4, 200222 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
- Niro, Scavone, Haller & Niro
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CPC
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US Classifications
Field of Search
US
- 345 11
- 345 32
- 345 196
- 345 507
- 345 212
- 345 509
- 345 213
- 345 545
- 345 547
- 345 552
- 348 718
- 348 4401
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International Classifications
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Abstract
The display system includes a display controller which renders text and graphics and writes it to the RAM. The display controller then reads the rendered information from the RAM and activates a display based upon that information. Generally the display controller reads information from the display controller and activates the display at a constant refresh rate; however, when a large number of text and/or graphics to be rendered have accumulated, the display controller temporarily reduces the refresh rate in order to render and write the text and/or graphics to the RAM.
Description
BACKGROUND OF THE INVENTION
The present relates to a display system and more particularly to a display system having an improved architecture for a graphics processor utilizing a single-port RAM.
Known display systems include a display controller driving a display having a matrix of pixels at a fixed refresh rate. The display controller drives the pixels based upon information stored in RAM or VRAM. Typically, between 4 and 32 bits of information are associated with each pixel in the display. The display controller is also a graphics processor which receives information, such as text or graphics-information, indicating text or graphics to be rendered and written into the RAM. After the text and graphics are written into the RAM, the display controller reads the rendered information from the RAM and activates the pixels in the display accordingly.
In order to reduce cost, a single-port RAM may be utilized. The single-port RAM cannot be written to and read from simultaneously. Further, the display controller will be accessing the RAM at a certain rate to maintain the refresh rate. Therefore, the amount of text and graphics which can be rendered and written to RAM in a given period of time is limited. As a result, there may be periods of significant delay before a large amount of text or graphics appear on the display.
SUMMARY OF THE INVENTION
The present invention provides a display system having a display controller which utilizes a single-port RAM. The display controller, based upon graphics and text codes from an external source, such as CPU, renders text and/or graphics and writes this information to the RAM. The display controller also reads information from the RAM and activates pixels on display based upon the information in the RAM.
Generally, the display controller reads from the RAM and activates pixels in the display at a constant refresh rate. However, when the number of text and/or graphics to be rendered by the display controller exceeds a predetermined threshold or has been delayed for a predetermined time period, the display controller reduces the refresh rate of the display, thereby permitting the display controller to render the text and/or graphics and write the rendered information to the RAM. When the display controller renders the text and/or graphics which have accumulated, the display controller returns to the original, higher refresh rate.
In this manner, a single port RAM can be utilized without significant reduction in display quality. The temporary reduction in refresh rate will be less noticeable than a significant delay in graphics and text rendering.
BRIEF DESCRIPTION OF THE DRAWING
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawing in which:
FIG. 1
is a schematic of the display system of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A display system
20
according to the present invention includes a display
22
, such as an ELD, activated by a display controller
24
. The display controller
24
reads and writes information to RAM
26
, such as the RAM, via a single port
30
. The display controller
24
also receives graphics and text codes from an external source, such as a CPU
32
. The codes indicate text and/or graphical information to be rendered by the display
24
and written to the RAM
26
.
The RAM
26
generally comprises a matrix of information
36
, each comprising between several bits or several bytes, each associated with a pixel
38
in a matrix of pixels
38
in display
22
. The display controller
24
activates the pixels
38
in the display
22
based upon information in the associated bytes
36
in the RAM
26
. The display controller
24
generally activates the pixels
38
in the display
22
at a generally constant, fixed first refresh rate, such as 120 Hertz. The display controller
24
includes a controller
40
, such as a microprocessor, and a local memory
44
having software run by the controller
40
to provide the features described herein.
The display controller
24
receives graphics and text codes from the CPU
32
, indicating text and/or graphics to be rendered by the display controller
24
. The codes may be stored in the memory
44
prior to being rendered by the controller
40
of the display controller
24
. If a predetermined amount of text and/or graphics to be rendered accumulate in the memory
44
, the display controller
24
reduces the refresh rate of the display
22
. During this time, the display controller
24
reduces the refresh rate temporarily, preferably not less than the critical flicker frequency and preferably by ½ to approximately 60 hertz. This also reduces the frequency at which the display controller
24
will have to read the RAM
26
via the single port
30
to refresh the display
22
. As a result, there is more time between the read cycles in which the display controller
24
can utilize the single port
30
to write the rendered text and/or graphics to the RAM
26
more promptly. It should be noted that each read cycle would still take the same amount of time during either mode, since there is the same amount of information to be read, but the read cycles would occur less frequently.
The use of the single port RAM
26
decreases the cost of the display system
20
. The temporary reduction in refresh rate may not be significantly noticeable, and according to the technique described above, the rendering of text and/or graphics by the display controller
24
will not be delayed by the use of the single port RAM
26
.
In accordance with the provisions of the patent statutes and jurisprudence, exemplary configurations described above are considered to represent a preferred embodiment of the invention. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
Claims
- 1. A display system comprising:a display having a matrix of pixels; a single port memory having a matrix of information, each associated with one of said pixels; a display controller writing display information to said memory, said display controller reading said display information and activating said display based upon said display information at a flicker frequency refresh rate, said display controller dynamically reducing said flicker frequency refresh rate when a quantity of display information to be written to said memory increases above a threshold quantity.
- 2. The display system of claim 1 wherein said display controller renders graphics, said rendered graphics comprising said display information.
- 3. The display system of claim 2 wherein said display controller reduces said refresh rate based upon a quantity of graphics to be rendered.
- 4. The display system of claim 1 wherein said display is an ELD.
- 5. A method for driving a display including the steps of:writing display information to a single port memory; reading said display information from the memory; activating a display based upon said display information at a flicker frequency refresh rate; and dynamically reducing said flicker frequency refresh rate when a quantity of said display information to be written increases above a threshold quantity.
- 6. The method of claim 5 further including the steps of:receiving a code; and rendering graphics based upon said code, said display information comprising said rendered graphics.
- 7. The method of claim 5 further including the steps of:activating said display at a first refresh rate when there are no graphics to be rendered; and activating said display at a second refresh rate less than said first refresh rate when a quantity of graphics to be rendered exceeds a predetermined threshold.
US Referenced Citations (10)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0 228 135 |
Jul 1987 |
EP |
09 325729 |
Mar 1998 |
EP |