US3792466A — Keyboard entry system with n-key rollover and n-k…

Claim 1

Independent Claim 380 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more keydetect signals are generated within the same scan cycle, said first validation means including first and second storage devices which are normally in a reset state, means for setting the first storage device in response to the first key-detect signal occurring during a cycle, means for setting the second storage device in response to a second key-detect signal occurring during the same scan cycle, and means for generating an error signal when both the first and the second storage devices are set within the same scan cycle.

Claim 2

Dependent Claim 380 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more keydetect signals are generated within the same scan cycle, said first validation means including first and second storage devices which are normally in a reset state, means for setting the first storage device in response to the first key-detect signal occurring during a cycle, means for setting the second storage device in response to a second key-detect signal occurring during the same scan cycle, and means for generating an error signal when both the first and the second storage devices are set within the same scan cycle.

Claim 3

Dependent Claim 23 words

A keyboard encoder array as in claim 1 including means for resetting the first and the second storage devices once each scan cycle.

Claim 4

Dependent Claim 55 words

A keyboard encoder array as in claim 2 wherein the first and the second storage devices are flip-flops, and the means for generating an error signal when both storage devices are set comprises a gate enabled by the set output of the second storage device to generate a signal at its output indicating an error.

Claim 5

Dependent Claim 333 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more key-detect signals are generated within the same scan cycle, and second validation means responsive to the output from said output terminal for generating an error signal when a key-detect signal has been generated in each of two consecutive scan cycles.

Claim 6

Dependent Claim 333 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more key-detect signals are generated within the same scan cycle, and second validation means responsive to the output from said output terminal for generating an error signal when a key-detect signal has been generated in each of two consecutive scan cycles.

Claim 7

Dependent Claim 44 words

A keyboard encoder array as in claim 4 wherein the second validation means include means for recording the key-detect signal generation history of consecutive scan cycles and for generating an error signal when a key-detect signal has been recorded in two consecutive scan cycles.

Claim 8

Dependent Claim 96 words

A keyboard encoder array as in claim 5 wherein the recording means include a serial shift register having at least two stages, each for one of two consecutive scan cycles, means for shifting through the shift register a first type logical signal for a scan cycle in which a key-detect signal is generated and a second type logical signal for a scan cycle in which no key-detect signal is generated, and means responsive to the presence of logical signals of the first type in the two stages of the shift register for generating an error signal.

Claim 9

Dependent Claim 326 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second state, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more key-detect signals are generated within the same scan cycle, and second validation means for generating a data-valid signal when a key-detect signal has been only generated in the second of three consecutive cycles.

Claim 10

Dependent Claim 326 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second state, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and first validation means responsive to the output from said output terminal for generating an error signal when two or more key-detect signals are generated within the same scan cycle, and second validation means for generating a data-valid signal when a key-detect signal has been only generated in the second of three consecutive cycles.

Claim 11

Dependent Claim 108 words

A keyboard encoder array as in claim 7 wherein the third validation means include a three-stage serial shift register, means for shifting into the register a first type logical signal for a scan cycle in which a key-detect signal has been generated and for shifting into the shift register a secoNd type logical signal for a scan cycle in which no key-detect signal is generated, and means responsive to the shift register contents for generating said data-valid signal when the register contains a first type logical signal in the center of its three stages and contains a second type logical signal in each of its two remaining stages.

Claim 12

Dependent Claim 293 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating an error signal when a key-detect signal is generated in each of two consecutive scan cycles.

Claim 13

Dependent Claim 293 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating an error signal when a key-detect signal is generated in each of two consecutive scan cycles.

Claim 14

Dependent Claim 300 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating a data-valid signal when a key-detect signal has been generated only in the second of a first, second and third consecutive scan cycle.

Claim 15

Dependent Claim 300 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating a data-valid signal when a key-detect signal has been generated only in the second of a first, second and third consecutive scan cycle.

Claim 16

Dependent Claim 343 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation logic means for successively recording key-detect signals generated in each of a first, second and third successive scan cycles and for generating a data-valid signal when a key-detect signal is recorded only for the second of the three consecutive scan cycles, and including means for enabling the keyboard encoder means to output the code corresponding to the key generating said key-detect signal only when a data-valid signal is generated.

Claim 17

Dependent Claim 343 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation logic means for successively recording key-detect signals generated in each of a first, second and third successive scan cycles and for generating a data-valid signal when a key-detect signal is recorded only for the second of the three consecutive scan cycles, and including means for enabling the keyboard encoder means to output the code corresponding to the key generating said key-detect signal only when a data-valid signal is generated.

Claim 18

Dependent Claim 302 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating an error signal when a key-detect signal is generated in each of two or more scan cycles of a predetermined number of consecutive scan cycles.

Claim 19

Dependent Claim 302 words

A keyboard encoder array to be interconnected with a keyboard matrix having keys each movable between a first and a second state to interrogate the keyboard matrix during successive scan cycles to detect keys in their second states, and to provide for each scan cycle a unique data signal identifying each key which is in its second state during that scan cycle but was not in its second state during the immediately preceding scan cycle, and for generating an error signal if two keys are in their second states for the first time during the same scan cycle, comprising: storage means for receiving data signals from a keyboard and for storing during each scan cycle the data signals representing the state of the keys during the cycle; comparison means for receiving data signals from the keyboard each scan cycle, said comparison means being coupled to said storage means for substantially simultaneously receiving data signals from said storage means representing the previous scan cycle, and for comparing the data signals received from the keyboard each scan cycle with the data signals stored during the immediately preceding scan cycle; an output terminal of said comparison means for generating a key-detect signal at any time the comparison means receives a data signal signifying a key to be in its second state but fails to receive a corresponding data signal for the same key for the previous scan cycle, thus identifying a key which is in its second state during the scan cycle but was not in that second state during the immediately preceding scan cycle, and thereby generating key-detect signals only for newly depressed keys, and validation means for generating an error signal when a key-detect signal is generated in each of two or more scan cycles of a predetermined number of consecutive scan cycles.

Claim 20

Dependent Claim 79 words

A keyboard encoder array as in claim 12 wherein said validation means comprises recording means for successively recording Key-detect signals generated in each of a predetermined number of successive scan cycles and for generating a data-valid signal when a key-detect signal is recorded in only one of said consecutive scan cycles, and including means for enabling the keyboard encoder means to output the code corresponding to the key generating said key-detect signal only when a data-valid signal is generated.

Claim 21

Dependent Claim 297 words

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 comparison 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 a 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 comparison circuit, circuit means 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 comparison 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 comparison circuit, the information train then stored in the storage device from the previous scan of the keyboard, the output terminal on said comparison 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.

Claim 22

Dependent Claim 297 words

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 comparison 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 a 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 comparison circuit, circuit means 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 comparison 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 comparison circuit, the information train then stored in the storage device from the previous scan of the keyboard, the output terminal on said comparison 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.

Claim 23

Dependent Claim 15 words

A keyboard encoder as in claim 14 wherein the storage device is a shift register.

Claim 24

Dependent Claim 75 words

A keyboard encoder as in claim 14 wherein the signals derived from the keyboard are digital in nature, being either of two levels depending upon whether or not a key is depressed, these signal levels representing the digits 1 and 0 respectively, and wherein the comparison circuit is a 0/1 detector in that it generates an output signal when the input signals on its first and second input terminals are a 1 and 0, respectively.

Claim 25

Dependent Claim 49 words

A keyboard encoder as in claim 14 further including gating means connected electrically to said keyboard and to the output terminal of the comparison circuit, said gating means operating to pass information signals received from said keyboard whenever it is supplied by a key-detect signal from said comparison circuit.

Claim 26

Dependent Claim 225 words

A real time N-key rollover protection logic circuit for generating a single signal for each new key depressed in a keyboard having a plurality of keys, whether or not previously depressed keys still remain depressed, comprising: storage means for receiving an information signal train from a keyboard representative of one complete scan of the keyboard, and containing a signal for each key that is depressed, a comparison circuit having first and second input terminals for receiving at its first input terminal a serial information signal train derived from a serial scan of the keyboard, while the keyboard is being scanned, and while the storage means is receiving the same information signal train, circuit means connecting the output of said storage means with the second input terminal of said comparison circuit, means for advancing the information signal trAin serially out of said storage means to the second input terminal of the comparison circuit, synchronously with the receipt at the first input terminal of the comparison circuit of a serial signal information train derived from a real time scan of the keyboard, and an output terminal of said comparison circuit for producing a key-detect signal whenever said first input terminal receives a key-depressed signal from a keyboard scan while the second input terminal fails to receive a corresponding key-depressed signal from the previous scan of the keyboard.

Claim 27

Dependent Claim 225 words

A real time N-key rollover protection logic circuit for generating a single signal for each new key depressed in a keyboard having a plurality of keys, whether or not previously depressed keys still remain depressed, comprising: storage means for receiving an information signal train from a keyboard representative of one complete scan of the keyboard, and containing a signal for each key that is depressed, a comparison circuit having first and second input terminals for receiving at its first input terminal a serial information signal train derived from a serial scan of the keyboard, while the keyboard is being scanned, and while the storage means is receiving the same information signal train, circuit means connecting the output of said storage means with the second input terminal of said comparison circuit, means for advancing the information signal trAin serially out of said storage means to the second input terminal of the comparison circuit, synchronously with the receipt at the first input terminal of the comparison circuit of a serial signal information train derived from a real time scan of the keyboard, and an output terminal of said comparison circuit for producing a key-detect signal whenever said first input terminal receives a key-depressed signal from a keyboard scan while the second input terminal fails to receive a corresponding key-depressed signal from the previous scan of the keyboard.

Claim 28

Dependent Claim 222 words

A keyboard encoder circuit for generating a signal representing the actuation of a key in the keyboard, including: scanning means for serially scanning the keys of the keyboard in successive scan cycles to provide in each scan cycle data signals serially generated which identify the state of actuation of each key, storage means for storing during each scan cycle the data signals representing the actuation states of the keys during the cycle, and for providing serially generated output signals during the next scan cycle representing the data signals stored during the previous scan cycle, the output signals being provided in time coincidence with the data signals generated by the scanning means during said next scan cycle, so that a stored data signal for a key is reproduced at the same time that the scanning means provides a new data signal for that same key, and gate means provided with the serially generated data signals and the output signals from said storage means for generating a key-detect signal upon receipt of both a data signal representing a key in an actuated state during a scan cycle and an output signal from said storage means representing the same key in a non-actuated state during the previous scan cycle, so as to generate key-detect signals only upon the initial actuation of keys in the keyboard.

Claim 29

Dependent Claim 222 words

A keyboard encoder circuit for generating a signal representing the actuation of a key in the keyboard, including: scanning means for serially scanning the keys of the keyboard in successive scan cycles to provide in each scan cycle data signals serially generated which identify the state of actuation of each key, storage means for storing during each scan cycle the data signals representing the actuation states of the keys during the cycle, and for providing serially generated output signals during the next scan cycle representing the data signals stored during the previous scan cycle, the output signals being provided in time coincidence with the data signals generated by the scanning means during said next scan cycle, so that a stored data signal for a key is reproduced at the same time that the scanning means provides a new data signal for that same key, and gate means provided with the serially generated data signals and the output signals from said storage means for generating a key-detect signal upon receipt of both a data signal representing a key in an actuated state during a scan cycle and an output signal from said storage means representing the same key in a non-actuated state during the previous scan cycle, so as to generate key-detect signals only upon the initial actuation of keys in the keyboard.

Claim 30

Dependent Claim 25 words

A circuit according to claim 19 in which the storage means comprises a shift register having n stages corresponding to a keyboard having n keys.

Claim 31

Dependent Claim 48 words

A circuit according to claim 19 including means for generating an error signal when at least one key-detect signal corresponding to an actuated key in the keyboard is generated during each of two or more scan cycles within a period including a predetermined number of consecutive scan cycles.

Claim 32

Dependent Claim 48 words

A circuit according to claim 21 in which said error signal generating means comprises a plurality of storage devices each set in response to key-detect signals in different scan cycles, and means responsive to the setting of a plurality of said storage devices for generating said error signal.

Claim 33

Dependent Claim 96 words

A keyboard encoder circuit for generating a signal representing the actuation of a key in the keyboard, including: interrogation means for electrically interrogating the keys of the keyboard in rapid successive interrogation cycles to provide in each interrogation cycle key-actuation signals which identify the keys in the keyboard that are in an actuated state, means for generating a first error signal when at least one key-actuation signal corresponding to an actuated key in the keyboard is generated during each of a plurality of scan cycles within a period including a predetermined number of consecutive scan cycles.

Claim 34

Dependent Claim 96 words

A keyboard encoder circuit for generating a signal representing the actuation of a key in the keyboard, including: interrogation means for electrically interrogating the keys of the keyboard in rapid successive interrogation cycles to provide in each interrogation cycle key-actuation signals which identify the keys in the keyboard that are in an actuated state, means for generating a first error signal when at least one key-actuation signal corresponding to an actuated key in the keyboard is generated during each of a plurality of scan cycles within a period including a predetermined number of consecutive scan cycles.

Claim 35

Dependent Claim 49 words

A circuit according to claim 23 in which said error signal generating means comprises a plurality of storage devices each set in response to key actuation signals in different scan cycles, and means responsive to the setting of a plurality of said storage devices for generating said error signal.

Claim 36

Dependent Claim 27 words

A keyboard encoder circuit according to claim 24 including means responsive to the setting of only one of said storage devices for generating a valid data signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1977-02-11	1977-08-13	1978-02-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1981-02-11	1981-08-13	1982-02-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1985-02-11	1985-08-13	1986-02-12	$7700.00	Window Closed / Lapsed

Keyboard entry system with n-key rollover and n-key lockout protection

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