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Partial scrolling video generator

  • US 4,342,991 A
  • Filed: 04/10/1980
  • Issued: 08/03/1982
  • Est. Priority Date: 03/10/1980
  • Status: Expired due to Term
First Claim
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1. A method for use in scrolling display rows in a raster scan type cathode ray tube display system wherein the display system includes a video display, refresh logic, a refresh memory, a first counter and a second counter, said refresh memory having storage locations arranged in a first matrix and a second matrix, said first matrix comprising storage for indirect address pointers of preselected base address locations for rows of said second matrix, said second matrix comprising fixed address storage for data to be presented for output to said video display, said method comprising the steps of:

  • (a) writing a base address pointer for each row into said first matrix;

    (b) reading, according to an address value in said first counter, a base address pointer from a location in said first matrix which points to the base address of a row in said second matrix so as to supply the base address to the address input of said refresh memory;

    thereupon(c) reading for output to said video display, according to a value in said second counter containing the current column address, data in said second matrix at the current column and row address;

    (d) incrementing said second counter containing the current column and row address to advance the column address;

    (e) repeating steps (c) and (d) until the end of the row is serviced;

    (f) incrementing said first counter to access a next sequential address in said first matrix;

    (g) repeating steps (b) through (f) to present a plurality of rows of data in said second matrix to said video display.

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