Resources Contact Us Home
Video memory system

Image Number 6 for United States Patent #4644495.

An improved video memory system includes a program memory, a display data memory, and a plurality of data fetchers. The data fetchers are used to indirectly address the display data in the display data memory. The data fetchers are programmed during vertical blanking so that selected display data is fetched at selected vertical display positions. During each scan line each data fetcher is "read" by: (1) decrementing a counter in the data fetcher; (2) comparing the counter value against preselected top and bottom values; and (3) using the counter value to indirectly address display data that is to be displayed on the current scan line if the counter value is between the top and bottom values. This relieves the host computer of having to keep track of the current vertical display position, thereby freeing it to use the saved computer cycles to produce more interesting viedo games with more complex display graphics. In addition there are provided data fetchers that can be programmed to periodically issue signals usable either for drawing a line with a predefined slope or modulating the amplitude of a sound generator.

  Recently Added Patents
Information processing apparatus and power supply controlling method
Power transmission control device for vehicle
Systems and methods for implementing pressure sensitive keyboards
System for setting programmable parameters for an implantable hypertension treatment device
Image forming apparatus and warming up method thereof
Ink, ink jet recording method, ink cartridge, and ink jet recording apparatus
Account and customer creation in an on-line banking model
  Randomly Featured Patents
Device for mounting/demounting spare tire for automobile
Towing apparatus with multiple adjustments wheel retainers
Ski having upper and lower surfaces of differing width
Method and apparatus for routing data to/from a mobile user
Method of producing exchange coupling film and method of producing magnetoresistive sensor by using the exchange coupling film
Static power conversion method and apparatus having essentially zero switching losses and clamped voltage levels
Opto-mechanical scanner with fixed-field ranging device
Inkjet image forming apparatus and spitting method therefor
Stabilized aqueous formaldehyde solutions and process for their manufacture
Self seeking neutralling arrangement for a power assisted cleaner