| 摘要 |
A video controller receives character data, attribute data and font data, each of which are stored in different planes of a video memory. The font data comprises bit maps of at least two character fonts, which may be user fonts or default fonts loaded from a controller BIOS. The video controller retrieves the font data, translates the font data into a page mode, and stores the font data in a hidden font cache in an unused portion of the video memory. The paged font data is divided into a number of pages equal to the number of scan lines per character. Each page contains a number of words, and each word contains at least two bytes. Each byte represents one scan line of a character in a different font. The video controller retrieves the paged fonts in page mode and assembles the scan lines for the characters to be displayed into one video scan line. The use of the page mode increases refresh rate and allows simultaneous display of two fonts.
|
