Computer graphics processing and selective visual display system – Computer graphics display memory system – Graphic display memory controller
Reexamination Certificate
2001-12-26
2004-08-10
Tung, Kee M. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics display memory system
Graphic display memory controller
C345S658000, C382S297000, C382S305000, C358S001100, C358S444000
Reexamination Certificate
active
06774902
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a memory control apparatus and method which write image data into a memory having a plurality of banks by interleaving, and read out the image data from the memory in an address sequence different from that in the data write.
BACKGROUND OF THE INVENTION
Some image output apparatuses such as copying apparatuses have a memory called an image memory for storing image data. A dynamic RAM (DRAM) has been conventionally used as an image memory for use in such apparatuses.
Recently, however, with the increasing resolution and transfer rate of image data, it is becoming necessary to increase the rates at which image data is input to and output from an image memory. As a DRAM meeting this requirement of high speed, a synchronous DRAM (to be referred to as an “SDRAM” hereinafter) is attracting attention. This SDRAM has a plurality of memory areas (to be referred to as “banks” hereinafter) in the same chip, and these banks can be accessed as they are switched, i.e., these banks can be interleaved.
Since a plurality of banks of the SDRAM are accessed while they are alternately interleaved, the access time can be shortened compared to a DRAM in which a single bank is continuously accessed. Therefore, the SDRAM is a memory capable of high-speed data transfer.
“Rotational output” by which the output direction of image data is rotated in accordance with the original size is one function of an image output apparatus such as a copying apparatus. This output function is used when no copying sheet optimum for the original size is set or when a plurality of original images are to be laid out on the same output sheet. For example, when an A4-size original is set on an original glass plate and there is no A4-size sheet, the scanned original image data is rotated 90° and output onto an A4R sheet.
Unfortunately, when rotation control is to be performed for this rotational output of image data, image data written in an image memory must be read out in an address sequence different from that in the data write. Even when high-speed write is realized by writing image data into the SDRAM as an image memory by interleaving banks of this SDRAM, the same bank may be continuously accessed during data read. This prolongs the access time of memory read during the rotation control.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problem, and has as its object to provide a memory control apparatus and method which can prevent continuous access from the same bank during memory read, and which thereby allow high-speed data access even when original image data is rotated.
As a means for achieving the above object, the present invention includes a memory control apparatus for writing image data into a memory having a plurality of banks by interleaving, and reading out the image data from the memory in an address sequence different from the address sequence of write, comprising: calculating means for calculating an effective pixel count (N) in a horizontal direction of original image data; determining means for determining whether the effective pixel count (N) calculated by the calculating means is a natural number multiple of the number (B) of the banks; and write control means for performing control such that original image data to which invalid image data is added in the horizontal direction is written in the memory, if the determining means determines that the effective pixel count (N) is a natural number multiple of the number (B) of the banks.
It is another object of the present invention to provide a memory control apparatus and method which can prevent alternate access from two banks during memory read, and which thereby allow high-speed data access even when original image data is rotated.
As a means for achieving the above object, the present invention includes a memory control apparatus for writing image data into a memory having a plurality of banks by interleaving, and reading out the image data from the memory in an address sequence different from the address sequence of write, comprising: calculating means for calculating an effective pixel count (N) in a horizontal direction of original image data; determining means for determining whether the effective pixel count (N) calculated by the calculating means satisfies a relation N=B×K+B/2 (K: natural number, B: the number of banks); and write control means for performing control such that original image data to which invalid image data is added in the horizontal direction is written in the memory, if the determining means determines that the relation N=B×K+B/2 holds.
It is still another object of the present invention to provide a memory control apparatus and method which can prevent continuous access from the same bank and can interleave during memory read, and which thereby allow high-speed data access even when original image data is rotated.
As a means for achieving the above object, the present invention includes a memory control apparatus for writing image data into a memory having a plurality of banks by interleaving, and reading out the image data from the memory in an address sequence different from the address sequence of write, comprising: determining means for determining, when original image data is written in the memory, whether bank addresses in each of pixel columns arranged in a horizontal direction are the same in a vertical direction; and address control means for performing address control, if the determining means determines that bank addresses in each of the pixel columns arranged in the horizontal direction are the same in the vertical direction, such that the original image data is written while the bank addresses are switched in the vertical direction.
The present invention has been made to solve the above problem, and has as its object to provide an image input/output control apparatus and an information notification method which can prevent continuous access from the same bank during memory read without exchanging any complicated signals with a memory controller, and which thereby can readily execute high-speed data access even when original image data is rotated.
As a means for achieving the above object, the present invention includes an image input/output control apparatus which is connected to a memory control apparatus for writing image data into a memory having a plurality of banks by interleaving, and reading out the image data from the memory in an address sequence different from the address sequence of write, and which notifies the memory control apparatus of information for accessing the memory, comprising: calculating means for calculating an effective pixel count (N) in a horizontal direction of original image data; determining means for determining whether the effective pixel count (N) calculated by the calculating means is a natural number multiple of the number (B) of the banks; and notifying means for notifying the memory control apparatus that the pixel count in the horizontal direction of the original image data is N+C (1≦C<B, C: natural number), if the determining means determines that the effective pixel count (N) is a natural number multiple of the number (B) of the banks.
The present invention has been made to solve the above problem, and has as its object to provide a copying apparatus and a memory control method of the copying apparatus which can prevent continuous access from the same bank during memory read, and which thereby can avoid data access delay during rotation control of read image data.
As a means for achieving the above object, the present invention includes a copying apparatus having: a reader for reading image data; a synchronous DRAM for storing the image data read by the reader into B banks; a memory controller for rotating image data through +90° or −90° by sequentially writing the image data into a memory having a plurality of banks by interleaving, and reading out the image data from the memory in an address sequence different from the address
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tung Kee M.
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