N-Key rollover keyboard

A keyboard comprising a plurality of selectively operable matrix elements each having an actuated stated and unactuated state, output means for scanning and sensing the state of each of said matrix elements in a sequential cyclic manner, memory means coupled to said output means for temporarily storing the sensed state of each of said matrix elements, output indicating means coupled to said output means for receiving a first signal representative of the state that the matrix element being scanned is in during the current scan cycle and coupled to said memory means for receiving a second signal representative of the state that the matrix element being scanned was in during the previous scan cycle, said output indicating means being constructed to provide an output data representation only when said first signal is representative of an actuated state of said scanned matrix element and the second signal is representative of an unactuated state of said scanned matrix element, said output means comprising a threshold means coupled to said matrix elements and to said memory means and feedback means coupled to said memory means for transmitting a feedback signal representative of the state that the matrix element being scanned was in during the previous scan cycle, said feedback signal providing a first level to said threshold means when said feedback signal is representative of an unactuated state of said scanned matrix element and a second level to said threshold means when said feedback signal is representative of an actuated state of said scanned matrix element.

A keyboard encoder for generating a signal for each new key depressed in a keyboard having a plurality of keys, whether or not a previously depressed key still remains depressed, comprising:

• scanning means for serially scanning each key of the keyboard along a predetermined scan pattern to produce a signal information train containing one time interval for each of the keys of the keyboard, and containing within each such time interval a signal if the corresponding key is depressed, a circuit having at least first and second input terminals and an output terminal for generating an output signal whenever a signal appears on its first input terminal and not on its second input terminal, a storage device having storage capacity at least sufficient to store a number of signals equal to the number of keys of the keyboard, the output of said storage device being electrically connected to the second input terminal of the circuit, said circuit coupling said scanning means to said storage device for supplying said signal information train to said storage device to store therein information signals corresponding to one complete scan of the keyboard, circuit means coupling said scanning means to the first input terminal of said circuit for supplying said signal information train serially to said first input terminal, and means for synchronously advancing out of the storage means to the second input terminal of the circuit the information train then stored in the storage device from the previous scan of the keyboard, the output terminal on said circuit generating a key-detect signal when said first input terminal receives a signal from the present scan of the keyboard while the second input terminal fails to receive a signal from the corresponding key in the previous scan.

Apparatus for generating a plurality of pulses in a pulse train, each of said pulses being encoded in time position in response to actuation of one of a plurality of keys of an instrument, comprising in combination:

• a plurality of ferromagnetic cores arranged in a matrix having two sets of intersecting conducting lines, each of said cores occupying a position juxtaposed with an intersection of said sets;
• a magnetic field generator for normally maintaining each of said cores in saturated condition to render it incapable of transforming a signal from a line of said first set to a line of said second set;
• a movable member connected with each of said keys for selectively unsaturating one of said cores to permit said core to transform a signal from a line of said first set to a line of said second set;
• and a driver connected to one of said sets of lines for successively energizing individual ones of said cores to produce said pulse train in accordance with operated ones of said keys.

In an electronic instrument having a plurality of selectively operable actuating members including selectively operable keys and control actuators, the combination comprising:

• a matrix formed with a plurality of conducting lines arranged in first and second sets, the lines of the first set intersecting the lines of the second set;
• a plurality of ferromagnetic core members juxtaposed with intersections of said matrix;
• a driver for applying pulses sequentially to the lines of said first set;
• enabling means for sequentially enabling the lines of said second set to successively and individually scan said core members;
• a plurality of movable magnetic field generators connected with said actuating members for selectively being movable to a position enabling individual ones of said core members to transform signals from the lines of said first set to the lines of said second set;
• and means connected to said matrix for producing output signals, when pulses are applied to said core members over the lines of said first set, in response to each enabled magnetic core member which is juxtaposed with an intersection of an enabled line of said second set.