ELECTRONIC KEYBOARD INPUT CIRCUIT

• US 3,662,378 A
• Filed: 06/01/1970
• Issued: 05/09/1972
• Est. Priority Date: 06/01/1970
• Status: Expired due to Term

• Current Assignee: Cherry Corporation (ZF Electronics Corp.)
• Original Assignee: Guy Macarthur
• Inventors: MacArthur, Guy
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Gnuse, Robert F.
• Application Number:
  US05/041,798
• Time in Patent Office: 708 Days
• Field of Search: 340/347DD 178/26R,26A
• US Class Current: 341/86
• CPC Class Codes: H03M 11/14 by using additional keys, e.g. shift keys, which determine the function performed by the multifunction key
• CPC Class Codes: H03M 11/20 Dynamic coding, i.e. by key scanning H03M11/26 takes precedence

Abstract

A continuously running astable multivibrator (clock) operates on electronic counter for 2n counts, (n) being a variable dependent upon the number of bits in the code being provided. A key closure in a keyboard matrix provides a continuity path between a decoder circuit which senses the least significant bits of the counter, and a multiplexer or multiplexers which sense the most significant bits. The multiplexer provides an output which effectively stops the clock at the desired code, thereby locking the clock out as long as the key is depressed and effectively rejecting multiple key inputs.

Claims

1. An electronic keyboard input circuit having a continuous code generated by a continuously cycling binary coded decimal counter generating a desired code and having a plurality of outputs including a. a multivibrator having a clocked frequency of 2,500 cycles per second to 3.5 megacycles divided by an inverter and a plurality of flip-flop devices to provide a two-phase clocking, with the phases 90* apart and adapted to detect a code and inhibit a change in said binary counter, b. decoder means for continuously scanning certain of said plurality of outputs of said binary counter to produce a change in each of its output lines for each combination of binary inputs, c. multiplexing devices continuously scanning certain other of said plurality of outputs of said binary counter, d. code switches in the circuit for establishing a continuity path between said multiplexing devices and said decoder means, and e. a gate in said circuit through which clock pulses from said multivibrator pass until one of said code switches is closed, establishing a continued path between said decoder means and said multiplexing devices to cause an input to said gate for inhibiting the clocking pulses to pass into said binary counter.

2. An electronic keyboard input circuit as defined by claim 1 and which includes a one-shot multivibrator having a variable output pulse time to detect an output from said multiplexing devices so as to produce an output pulse to said gate, controlling said means for clocking said counter, and having an output pulse of a variable time delay, providing a pulsed strobe from said one-shot multivibrator to actuate said gate in said counter output lines and another pulsed strobe to be used as a repeating function.

3. An electronic keyboard input circuit as defined by claim 1 wherein multiple codes can be generated from a single code switch means closure through a plurality of multiplexing devices connected in circuit to respond to a specific code when a strobe line is enabled or by a change in the bits scanned by said multiplexing devices and said decoder means through a combination of logic gates and control keys.