Drawing processor including arithmetical unit for improved super

Details Drawing processor including arithmetical unit for improved super Drawing processor including arithmetical unit for improved super

1989-12-12

1992-04-28

Clark, David L.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340703, 364749, 364786, G06F 314

Patent

active

051094800

ABSTRACT:
A color graphic display system is disclosed including a drawing process for displaying video data on a display device wherein the data is particularly intended to include superposed pictures. The processor includes an arithmetical operation unit which will allow addition/subtraction of video data items representative of the picture elements to be superposed. Further included is a condition setting circuit for selectively inhibiting carrys or borrows during the arithmetical operations between selected bits of a data word representative of an element such as a pixel of the picture being displayed. More particularly, where a video data item is comprised of sets of bits each set of which is representative of a main color of the pixel, and when two video data items are added or subtracted, the carrys that may normally occur between the different sets are inhibited to avoid interference between the sets that may affect the color of the resulting video data item. A carry look-ahead circuit is also provided for improved processing speed of the system. An overflow prevention circuit is disclosed for forcibly switching selected bits of the video data item to a preselected value upon determining that an operated result has given rise to an overflow.

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Kazuo Minorikawa, et al., "A CRT Controller with a Variety of Commands Such as PAINT and COPY, and Which can Specify Drawing Positions with Coordinates", Thesis--May 21, 1984, published by Nikkei McGraw-Hill Kabushiki-Kaisha, pp. 221-254.
An English translation is provided.

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