Video font cache

Claim 2

A video controller for receiving alphanumeric character data and generating alphanumeric characters for a video display said video controller comprising: a video memory for storing alphanumeric character data, each of said alphanumeric character data representing at least one character of a character set, character attribute data including at least font selection data, and at least two character font bit maps, each of said at least two character font bit maps representing a display font; a video font cache for storing said at least two character font bit maps in a page mode; and a video memory controller, coupled to said video memory and said video font cache, for receiving said at least two character font bit maps from said video memory and reformatting said at least two character font bit maps in said font cache; wherein each page of said paged character font bit maps comprises one scan line for each display font of each character of said character set.

Claim 3

The video controller of claim 1, wherein said memory controller receives at least one of said alphanumeric character data and corresponding attribute data and retrieves a scan line corresponding to both said at least one alphanumeric character data and a display font selected by font selection data in said attribute data.

Claim 6

The method of claim 3, further comprising the steps of: retrieving at least one character datum representing one character of a character set; retrieving at least one attribute datum corresponding to said at least one character datum, said at least one attribute datum including at least font selection data; retrieving in page mode, one page of said paged character font bit map; retrieving at least two scan lines corresponding to said at least one character datum from said retrieved one page of said paged character font bit map, each of said at least two scan lines corresponding to said at least two character fonts; and selecting, from said retrieved at least one attribute datum, one scan line from said retrieved at least two scan lines.

Claim 7

The method of claim 4, further comprising the steps of: scanning said selected one scan line onto a video display.

Claim 8

The method of claim 4, wherein said at least one character datum comprises eight bits of ASCII data.

Claim 9

The method of claim 4, wherein said at least one attribute datum comprises eight bits of data indicating at least font selection, foreground color, background color, underlining, and blinking of a corresponding character.

Claim 10

The method of claim 3, wherein each scan line bit map is comprised of a plurality of bytes, each byte comprising eight bits of pixel data representing one scan line of a character font on a video display.

Claim 11

The method of claim 3, further comprising the steps of: monitoring said video memory for a change in either of said at least two character font bit maps; reformatting, in response to a detected change in either of said at least two character font bit maps, said character font bit maps into a page mode to produce paged character font bit maps such that each page of said paged character font bit maps comprises one scan line for each character of a character set in each character font.

Claim 12

The method of claim 9, wherein said video memory is arranged into at least three bit planes and wherein said at least one character datum is stored in a first plane, said at least one attribute data is stored in a second plane, and said at least two character font bit maps are stored in a third plane.

Claim 13

The method of claim 10, wherein said step of monitoring comprises the step of monitoring said video memory to detect de-selection of said first and second planes of said video memory and selection of said third plane of video memory to detect a change in either of said at least two character font bit maps.

Claim 14

The method of claim 10, further comprising the preliminary steps of: monitoring said video memory to determine whether said video controller is in an alphanumeric mode.

Claim 15

The method of claim 12, wherein said step of monitoring further comprises the steps of monitoring said video memory to detect selection of said first and second planes of said video memory and de-selection of said third plane of video memory to detect a change in either of said at least two character font bit maps.

Claim 16

The method of claim 3, wherein said paged character font bit maps comprise a number of pages of font data, each page of said paged font data corresponding to one scan line of each character of a character set; each page further comprising a number of words equal to the number of characters in the character set, each word comprising a number of bytes corresponding to the number of at least two fonts, each byte representing pixel data from one scan line of a character.

Claim 17

The method of claim 14, wherein each byte comprises eight bits, each bit representing pixel data for a scan line on a video display.

Claim 20

The apparatus of claim 16, wherein said video controller further comprises: character generating means, coupled to said video memory and said font cache, for retrieving said character data and at least one page of said font cache and generating a scan line of pixel data from said at least one page of said font cache, said scan line of pixel data representing a scan line of characters corresponding to said retrieved character data.

Claim 21

The apparatus of claim 17, further comprising: video display means, coupled to said video controller, for receiving said scan line of pixel data and generating a video image from said scan line of pixel data.

Claim 22

The apparatus of claim 16, wherein said video controller further comprises: read only memory means, for storing default font data, wherein said video controller transfers said default font data to said video memory.

Claim 23

A video controller for receiving alphanumeric character data and generating alphanumeric characters of a video display, said video controller comprising: a video memory, comprising: a first memory plane for storing alphanumeric character data, each of said alphanumeric character data representing at least one character of a character set, a second memory plane for storing character attribute data including at least font selection data, a third memory plane for storing at least two character font bit maps, each of said at least two character font bit maps representing a display font, and a video font cache for storing said at least two character font bit maps in a page mode; and a video memory controller, coupled to said video memory, for receiving said at least two character font bit maps from said video memory and reformatting said at least two character font bit maps into a page mode to produce paged character font bit maps and storing said paged character font bit maps in said font cache; wherein each page of said paged character font bit maps comprises one scan line for each display font of each character of each character set, and said at least two character font bit maps are stored in said third memory plane by an external host processor in an unpaged mode.

Claim 24

A video controller for receiving alphanumeric character data and generating alphanumeric characters of a video display, said video controller comprising: a video memory, comprising: a first memory plane for storing alphanumeric character data, each of said alphanumeric character data representing at least one character of a character set, a second memory plane for storing character attribute data including at least font selection data, a third memory plane for storing at least two character font bit maps, each of said at least two character font bit maps representing a display font, and a video font cache for storing said at least two character font bit maps in a page mode; and a video memory controller, coupled to said video memory, for receiving said at least two character font bit maps from said video memory and reformatting said at least two character font bit maps into a page mode to produce paged character font bit maps and storing said paged character font bit maps in said font cache; wherein each page of said paged character font bit maps comprises one scan line for each display font of each character of each character set, and said at least two character font bit maps are stored in said third memory plane by an external host processor in an unpaged mode.