Data transfer apparatus and data transfer method

A data transfer apparatus comprising:

• a cache memory having a storing portion for writing and reading data at a higher speed than storing circuitry which stores image data on a predetermined image;
• and
• transfer request circuitry for outputting, to said cache memory, a transfer request for image data in a certain region in said predetermined image,
• said cache memory including:
• reading control circuitry for deciding, for every pixel row, whether image data in a pixel row included in said certain region corresponding to said transfer request is stored in said storing portion of said cache memory or not and reading unstored image data of the predetermined image, which is not stored in said storing portion, from said storing circuitry beyond said certain region in a row direction in said predetermined image for every pixel row;
• storing control circuitry for storing, in said storing portion, the unstored image data for said pixel row, read by said reading control circuitry, with a storage destination changed for every pixel row;
• and
• output control circuitry for reading image data in a certain region corresponding to said transfer request, from said storing portion, and outputting the image data to said transfer request circuitry, wherein
• said transfer request circuitry sequentially gives a transfer request for image data in each of said certain regions arranged in a horizontal direction of said predetermined image in arrangement order in said horizontal direction,
• a volume of said unstored image data of said predetermined image is a volume of data obtained from a region longer than a maximum width, in said row direction, of said row direction of said certain region.