Keyboard circuit
AssigneeTektronix, Inc.
InventorsJohn Laurence Melanson, Richard Allen Springer, Jack Duane Grimes, Jack Arthur Gilmore
Life of this patent
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Abstract
A simplified keyboard for a terminal device, calculator, or the like, in which each key is sequentially scanned and parallel key code data is sent to an entry register. A pair of flip-flops in combination with firmware ascertain that only valid key code data is sent to the entry register for utilization by the system, providing double entry and key bounce protection. The firmware further provides N-key rollover and auto repeat with a variable repeat rate, and expands the keyboard from a single-mode to an eight-mode capability.
Claims4
A keyboard circuit for an associated data processing device, comprising:
- an array of keys;
- means for scanning cyclically said array of keys in a predetermined sequence and generating parallel keycode data corresponding to each key;
- interrupt control means for sensing a key depressed for two successive scans and generating an interrupt signal in response thereto;
- and
- means responsive to said interrupt signal for generating an acknowledge signal to stop said scanning at said depressed key on the second of said two successive scans and for reading and storing keycode data corresponding to said depressed key.
Dependencies are inferred from the claim text.