Edward Asam

US Patent:

46334157, Dec 30, 1986

Filed:

Jun 11, 1984

Appl. No.:

6/619373

Inventors:

Anthony B. Vink - Canton MI
Edward F. Asam - Ann Arbor MI
Dewayne J. Ferris - Brighton MI

Assignee:

Northern Telecom Limited - Montreal

International Classification:

G06F 314
G09G 100

US Classification:

364521

Abstract:

A method and a circuit for producing an independent scrollable display region (sometimes referred to as a "window") on the face of a cathode-ray tube (CRT) in a bit-mapped data display system is disclosed. Circuitry is provided to detect the presence of the window along a vertical axis and to detect the presence of the window along a horizontal axis. When both a vertical and a horizontal presence are detected simultaneously, a window is deemed to be present. When the window is deemed to be present a memory address selection circuit selects memory addresses from one memory address circuit and when the window is deemed to be not present, the memory address selection circuit selects memory addresses from another memory address circuit.