High speed serial scan and readout of keyboards

Abstract

Relates generally to the production of electrical signals from a keyboard, each key of which is individually operatively associated with a switching device whose activation to electrical conductive condition is controlled by the displacement of the key. These switches are hermetically sealed from the atmosphere and are electrically scanned in succession at relatively high speeds and at a repetitious rate such that several scanning cycles occur during the normal activation of a selected key. The keyboard mechanism also includes a shift register having one more bit position than the number of switch devices and into which a bit is introduced into the "one" position at the instant the scan encounters a closed switch of the keyboard. This bit is then shifted through the register in timed relation to the scan of the remaining key switches and unloaded into the last bit position of the register. A detector senses the presence of a bit in both the "one" position and the last position of the shift register and upon detection of a bit solely in the one position it delivers a signal indicative of the character represented by the actuated key and upon detecting bits in the two extreme positions of the shift register it nullifies the delivery of such a signal.

What is claimed is: 
     
       1. A keyboard operated machine including a plurality of actuatable keys each being operable from a normal inactive position to an actuated position and a plurality of pairs of normally spaced apart contacts each pair being individually associated with a key of the keyboard and responding to actuation of its key by engaging one another, a shift register of N+1 stages wherein N is the number of keys in the keyboard,   means for sequentially electrically pulsing the pairs of contacts of the keyboard in succession and operable upon detection of an engaged pair of contacts for immediately entering a bit into the "one" stage of the shift register,   means for continuously repeating the sequential pulsing of said plurality of pairs of contacts at a rate such that more than one such pulsing cycle occurs during a normal actuation of a key of the keyboard,   means for shifting a bit entered into the "one" stage of the register through register to the N+1 stage in timed relation to the successive pulsing of the contacts of the keyboard, and   circuit gating means connected to the outputs of the "one" stage and the N+1 stage of the shift register and being operable to transmit an intelligence signal to a utilization device when a bit appears only in the "one" stage of the shift register but inhibiting the transmission of such an intelligence signal when a bit concurrently appears in both the "one" stage and the N+1 stage of the shift register.   
     
     
       2. In a keyboard operated machine including a plurality of actuatable keys each being operable from a normal inactive position to an actuated position in engagement with an actuated contact to send an intelligence signal, the invention which comprises: a shift register of N+1 stages wherein N is the number of keys in the keyboard;   means for repetitively scanning the contacts of the keyboard in succession and operable upon detection of an actuated contact of the keyboard for instantly entering a bit into the "one" stage of the shift register;   means for shifting the bit through the register in timed sequence with the scanning of the contacts of the keyboard and entering the bit into the N+1 stage thereof; and   circuit gating means connected to the outputs of the "one" stage of the N+1 stage of the shift register and being operable to transmit an intelligence signal to a utilization device signifying the character of the actuated key when a bit appears only in the "one" stage of the shift register but inhibiting the transmission of such an intelligence signal when a bit appears concurrently both in the "one" stage and the N+1 stage of the shift register.   
     
     
       3. The invention as set forth in claim 2 characterized in that the keys of the keyboard are manually actuatable and in that said scanning means repetitively scans the contacts of the keyboard at such a rate that more than one scanning cycle occurs during a normal manual actuation of the key. 
     
     
       4. In a code signal sender, a plurality of electrical contact pairs each pair being capable of assuming an opened circuit condition and a closed circuit condition;   a shift register comprised of at least as many stages as is the number of said plurality of contact pairs;   means for repetitively scanning said plurality of contact pairs in succession and upon detection of a closed pair for entering a bit into the first stage of the shift register and for shifting the bit through the register to the last stage thereof; and   circuit gating means connected to the first and last stages of the shift register and being operable to transmit a signal representative of any closed pair of contacts detected by said scanning means when a bit appears only .[.in.]. .Iadd.at .Iaddend.the first stage of the shift register but being inoperable to signal in such manner when a bit is .[.concurrently present in both.]. .Iadd.at .Iaddend.the first and .Iadd.in .]..Iaddend. the last .[.stages.]. .Iadd.stage .Iaddend.of the shift register.   
     
     
       5. In a code signal sender in accordance with claim 4 wherein the shift register is comprised of one more stage than is the number of the plurality of contact pairs. 
     
     
       6. In a code signal sender in accordance with claim 5 wherein said plurality of contact pairs are each individually associated with a different mechanically operable key of a keyboard and wherein means is responsive to the actuation of any one of said keys for causing its associated electrical contact pair to assume a circuit closed condition. 
     
     
       7. In a code signal sender in accordance with claim 6 wherein said scanning means repetitively scans the electrical contact pairs at such a rate that more than one scanning cycle occurs during the actuation of a key of the keyboard. 
     
     
       8. A keyboard operated machine including a keyboard having a plurality of actuatable keys each being operable from a normal inactive position to an actuated position and a plurality of pairs of normally spaced apart electrical contacts each pair being individually associated with a key of the keyboard and responding to actuation of its key by engaging one another, a shift register of N+1 stages wherein N is the number of keys in the keyboard,   means for sequentially electrically pulsing the pairs of contacts of the keyboard in succession and operable upon detection of an engaged pair of contacts for immediately entering a bit into the "one" stage of the shift register,   means for repetitively cycling the sequential pulsing of said plurality of pairs of contacts at a rate such that more than one such pulsing cycle occurs during a normal actuation of a key of the keyboard,   means for shifting a bit entered into the "one" stage of the register through the stages of the register to the N+1 stage in timed relation to the successive pulsings of the pairs of contacts of the keyboard, and   circuit means connected to the "one" stage and to the N+1 state of the shift register and being operable to transmit an intelligence signal to a utilization device when a bit appears only in the "one" stage of the shift register but inhibiting the transmission of such an intelligence signal when a bit concurrently appears in both the "one" stage and the N+1 stage of the shift register.   
     
     
       9. A code signal sender including, in combination; a plurality of pairs of electrical contacts, each contact pair representing a different character and being capable of assuming an opened circuit condition and a closed circuit condition;   means for sequentially scanning the plurality of electrical contact pairs for detecting a closed condition of any one of said contact pairs and generating a signal in response thereto;   means for generating an electrically coded representation of the character associated .[.witch.]. .Iadd.with .Iaddend.such a detected closed contact pair;   means operatively connected to said plurality of electrical contact pairs and responsive to said signal signifying the closed condition of any one of the contact pairs thereof for temporarily storing that signal until the contact pair producing such signal is scanned again;   means operatively connected to said storage means and operative to sense the initial storage of said signal responsive to such sensing for causing the transmission of the coded representation of the character associated with the closed contact pair responsible for the storage of the signal; and   means for sensing the presence of the signal in said storage means during a subsequent scan of the plurality of contact pairs for effectively preventing a repetitive transmission of the coded representation of the character associated with the closed contact pair responsible for the stored signal.   
     
     
       10. In a code signal sender in accordance with claim 9 wherein the signal storage means is a serial register comprised of at least one more stage than is the number of the plurality of contact pairs. 
     
     
       11. In a code signal sender in accordance with claim 10 wherein each contact pair of said plurality of contact pairs is individually associated with a key of a keyboard and wherein means is responsive to the actuation of any one of said keys for causing its associated electrical contact pair to assume a circuit closed condition. 
     
     
       12. In a code signal sender in accordance with claim 11 wherein said scanning means repetitively scans said electrical contact pairs at such a rate that more than one scanning cycle occurs during normal actuation of a key of the keyboard. 
     
     
       13. In a keyboard operated machine including a plurality of actuatable keys each being operable from a normal inactive position to an actuated position and further including a plurality of switches each associated with an individual one of the keys and responsive to the actuation of its associated key to change from circuit opened condition to circuit closed condition thereby to send an intelligence signal, the invention which comprises: a shift register of N+1 stages wherein N is the number of keys in the keyboard;   means for repetitively scanning said plurality of switches in succession and operable upon detection of a switch in circuit closed condition for instantly entering a bit into the "one" stage of the shift register;   means for shifting the bit through the shift register in timed sequence with the scanning of the switches and entering the bit into the N+1 stage thereof; and   means connected to the outputs of the "one" stage and the N+1 stage of the shift register and being operable to transmit an intelligence signal to a utilization device which is significant of the actuated key when a bit appears only in the "one" stage of the shift register but inhibiting the transmission of such an intelligence signal when a bit appears concurrently both in the "one" stage and the N+1 stage of the shift register.   
     
     
       14. The invention as set forth in claim 13 characterized in that the keys of the keyboard are manually actuatable and in that said scanning means repetitively scans the switches of the keyboard at such a rate that more than one scanning cycle occurs during a normal manual actuation of a key. 
     
     
       15. In a code signal sender, a plurality of electrical switches each being capable of assuming an open circuit condition and a closed circuit condition;   a shift register comprised of at least as many stages as is the number of said plurality of switches;   means for repetitively scanning said plurality of switches in succession and operable upon detection of a switch in closed circuit condition to enter a bit into the first stage of the shift register and for shifting the bit through the register to the last stage thereof; and   means connected to the first and the last stages of the shift register and being operable to transmit a signal representative of any such switch in closed circuit condition detected by said scanning means when a bit appears only in the first stage of the shift register, but being inoperable to transmit in such manner when a bit is .[.concurrently present in both.]. .Iadd.at .Iaddend.the first and .Iadd.in .Iaddend.the last stage.[.s of the shift register.   
     
     
       16. In a code signal sender in accordance with claim 15 wherein the shift register has one more stage than the number of switches in said plurality of switches. 
     
     
       17. An electrical signal sender including a plurality of electrical switches each being operable to assume a normal inactive condition and a temporary active condition; a shift register of N+1 stages wherein N is the number of said plurality of switches;   means for sequentially electrically pulsing said plurality of electrical switches in succession and operable upon detection of a switch in a temporary active condition for immediately entering a bit into the "one" stage of the shift register;   means for repetitively cycling the sequential pulsing of said plurality of switches at a rate such that more than one such pulsing cycle occurs during the temporary active condition assumed by any one of the plurality of switches;   means for shifting a bit entered into the "one" stage of the register through the stages of the register to the N+1 stage in timed relation to the successive pulsings of the plurality of switches; and   circuit means connected to the "one" stage and to the N+1 stage of the shift register and being operable to transmit an intelligence signal to a utilization device when a bit appears only in the "one" stage of the shift register, but being inoperable to transmit such an intelligence signal when a bit concurrently appears in both the "one" stage and the N+1 stage of the shift register.   
     
     
       18. A code signal sender including, in combination; a plurality of electrical switches each representing a different character and being capable of assuming a normal inactive condition and a temporary active condition; means for sequentially scanning the plurality of electrical switches for detecting a temporary active condition of any one of said switches and generating a signal in response thereto;   means for generating an electrically coded representation of the character associated with such a detected active conditioned switch;   means operatively connected to said plurality of electrical switches and responsive to an aforesaid signal signifying the active condition of any one of the switches thereof for temporarily storing that signal until the switch producing such signal is scanned again;   means operatively coupled to said character representation generating means and to said storage means and being operable to sense the initial storage of said signal in the storage means and being responsive to such sensing for causing the character representing generating means to transmit the coded representation of the character which is associated with the detected active conditioned switch to a utilization device; and   means for sensing the presence of the signal in said storage means during a subsequent scan of the plurality of switches for effectively preventing a repeated transmission of the coded representation of the character associated with the active conditioned switch responsible for the signal. .Iadd.   
     
     
       19.  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 an 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 during each said serial scan 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 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 information train serially to said first input terminal as the keyboard is being scanned, and   means for 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, synchronously with the signal information being received by the first input terminal from the current serial 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. .Iaddend. .Iadd.   
     
     
       20.  A keyboard encoder as in claim 19 wherein the storage device is a shift register. .Iaddend. .Iadd.21. A keyboard encoder as in claim 19 wherein the information derived from the keyboard is digital in nature, being either of two levels depending upon whether or not a key is depressed, these 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 on its first and second input terminals are 1 and 0, respectively. .Iaddend. .Iadd.22. A keyboard encoder as in claim 19 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 received from said keyboard whenever it is supplied by a key-detect signal from said comparison   
     
     
        circuit. .Iaddend. .Iadd.23.  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 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 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 train,   circuit means connecting the output of said storage means with the second input terminal of said comparison circuit,   means for advancing the information 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 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.   
     
     
        .Iaddend. .Iadd.24.  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 bits serially generated which identify the state of actuation of each key,   storage means for storing during each scan cycle the data bits 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 bits stored during the previous scan cycle, the output signals being provided in time coincidence with the data bits generated by the scanning means during said next scan cycle, so that a stored data bit for a key is reproduced at the same time that the scanning means provides a new data bit for that same key, and   gate means provided with the serially generated data bits and the output signals from said storage means for generating a key-detect signal upon receipt of both a data bit 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 the keys in the keyboard. .Iaddend.