Data transfer control apparatus and method

Abstract

An improved data transfer system enables a common data source to operate asynchronously with a plurality of different data receivers at a data transfer rate that is limited only by the operating rates of the data receivers and the data source. The operating conditions of the data receivers are sensed in common by the data source and the operating condition of the data source is sensed by the data receivers in order to optimize the data transfer rate without loss of data and without restriction to a predetermined (or synchronous) data transfer rate.

I claim: 
     
       1. Data transfer apparatus comprising: source means of data signals including register means for storing data signals to be transferred .[.;.]. .Iadd., said source means producing a logic signal after introduction of data signals into the register means and in response to an applied control signal, the logic signal being representative of the validity of data signals to be transferred; .Iaddend.   a number of data-receiving means for operating upon applied data signals from the source means .[.,.]. .Iadd.in response to appearance of said logic signal, .Iaddend.each of said number of data-receiving means including means for providing a first output indication of the operability thereof on applied data signals and means for providing a second output indication of the completed acceptance of applied data signals .[., independently of the operation thereof on such applied data signals.].;   means coupling data signals from said source means to each of said number of data-receiving means;   .[.  means responsive to the appearance of second outputs from all of said number of data-receiving means for terminating the data signals applied to each of said number of data-receiving means from said source means; and.].   means responsive to the appearance of said first outputs from all of said number of data-receiving means for applying a control signal to .[.a.]. .Iadd.the .Iaddend.source means .[.for introducing new data signals into said register means for application to all of said number of data-receiving means..]. .Iadd.; and   means responsive to the appearance of second outputs from all of said number of data-receiving means for applying a signal to said source means for terminating said logic signal and introducing new data signals into said register means. .Iaddend. .[.2. Data transfer apparatus as in claim 1 in which said source means includes logic means for producing a logic output representative of the validity of data signals supplied to all of the number of data-receiving means from the register means of the source means, said logic means produces said logic output after new data signals are introduced into the register means and the first outputs from all of the number of data-receiving means ar present;   all of said number of data-receiving means accept the data signals from the receiver means of said source means only in response to the appearance of said logic output; and   said logic means terminates said logic output in response to the appearance   
     
     
        of said outputs from all of said number of data-receiving means. .]. 3. Data transfer apparatus as in claim 1 comprising: a set of data signal lines coupling the register means of said source means to all of said number of data-receiving means and including a set of control lines coupled between all of said number of data-receiving means and said source means and including a data-valid (DAV) line, a ready-for-data (RFD) line and a data-accepted (DAC) line;   first gate means responsive to first outputs from all of said number of data-receiving means for applying to the source means a signal on said RFD line;   said source means being responsive to signal on said RFD line to produce a signal on the DAV line after introduction of data signals into the register means for coupling to all of said data-receiving means over said set of data signal lines;   each of said number of data-receiving means responds to signal on said DAV line and includes means for producing said second outputs after acceptance of such data signals; and   second gate means responsive to the second outputs from all of said data-receiving means for applying to the source means a signal on said DAC line;   said source means being responsive to signal on said DAC line to terminate the signal on said DAV line and to introduce new data signals into said   
     
     
        register means. 4. Data transfer apparatus as in claim 3 including detector means responsive to simultaneous presence of signals on said RFD and DAC lines for producing an output indication of the operating 
     
     
        condition of the data transfer apparatus. 5. Apparatus for operation in a data transfer system including a number of data-responsive units coupled to respond to data and control signals on data and control channels, the apparatus comprising: source means adapted to be coupled to data signal channels of a data transfer system for delivering valid data signals thereto;   logic means adapted to receive a first control signal from a control signal channel of a data transfer system which is indicative of the condition of readiness of all of the number of data-responsive units to receive data signals, said logic means being capable of delivering a second control signal to a control signal channel following receipt of such first control signal and the source means having delivered valid data signals, the second control signal having one logic state which is indicative of the validity of the data signals delivered by the source means; and   said logic means being adapted to receive a third control signal from a control signal channel of the data transfer system which is indicative of all of the number of data-responsive units having accepted data signals for altering the second control signal to a second logic state which indicates that data signals are not valid and for enabling the source   
     
     
        means to deliver updated data signals to data signal channels. 6. Apparatus as in claim 5 wherein said logic means enables said source means to deliver updated data signals to data signal channels within the interval from the appearance of a third control signal to the appearance 
     
     
        of a second control signal. 7. Apparatus as in claim 5 wherein said logic means enables said source means to deliver updated signals to data signal channels within the interval from the appearance of the .Iadd.second .Iaddend.control signal in the second logic state which indicates that data signals are not valid and the appearance of the second control signal in the one logic state which indicates that the delivered data signals are 
     
     
        valid. 8. Apparatus as in claim 5 comprising error detecting means responsive to the appearance simultaneously of the first control signal indicative of the condition of readiness and the third control signal indicative of all of the number of data-responsive units having accepted data signals for producing an output indication of an erroneous operating 
     
     
        condition of the data transfer system. 9. A data-responsive unit for operation in a data transfer system including a number of such data-responsive units which respond to data signals and control signals on data and control signal channels, the data-responsive unit comprising: data-receiving means capable of receiving data signals from a data signal channel of a data transfer system and being adapted to deliver to a control signal channel a first control signal having a first logic state which indicates preparedness to receive data signals;   sensing means adapted to be coupled to receive from a control signal channel of the data transfer system a second control signal having a first logic state which is indicative of the validity of data signals for enabling the data-receiving means to receive the valid data signals from the data signal channel and to change the first control signal to a second logic state which indicates unpreparedness to receive data signals;   logic means adapted to deliver to a control signal channel a third control signal having a first logic state indicative of having accepted the data signals;   said sensing means being responsive to said second control signal attaining a second logic state which indicates that data signals are not valid for changing the third control signal to a second logic state indicative of completion of a data transfer; and   said data-receiving means being responsive to the third control signal attaining the second logic state and being prepared to accept new data signals for changing the first control signal to said first logic state.   
     
     
          . A data-responsive unit as in claim 9 wherein said data-receiving means and said logic means are coupled to inhibit operations thereof 
     
     
        simultaneously in the associated first logic states thereof. 11. A data-responsive unit as in claim 9 wherein said data-.[.responsive.]. .Iadd.receiving .Iaddend.means includes operative means for manipulating applied data signals at a rate substantially independent of the rate at which data signals are applied, and including buffer means for retaining applied data signals for a period required by the operative means to manipulate data signals, said data-receiving means producing the first control signal in said first logic state in response to said buffer means being prepared to accept data, independently of the preparedness of the 
     
     
        operative means to manipulate data signals. 12. A data-responsive unit as in claim 9 comprising first gating means for cooperating with all similar first gating means associated with all of the remaining number of data-responsive units coupled to a common control signal channel for producing said first control signal on said common control signal channel only in response to all of the number of associated data-receiving means 
     
     
        being prepared to accept data signals. 13. A data-responsive unit as in claim 9 comprising second gating means for cooperating with all similar second gating means associated with all of the remaining number of data-responsive units coupled to a common control signal channel for producing said third control signal on said common control signal channel only in response to all of the number of associated logic means having 
     
     
        accepted the data signals. 14. Data transfer apparatus as in claim .[.2.]. .Iadd.1 .Iaddend.wherein: said means coupling data signals from said source means applies the data signals in parallel to each of said plurality of data-receiving means; and   a gate circuit is coupled to said source means and to each of said plurality of data-receiving means for a. terminating the data signals from said source means .[.in response to the appearance in common of all the second outputs from said plurality of data-receiving means.]., and   b. for activating said source means to apply successive data signals in parallel to said plurality of data-receiving means in response to the appearance in common of said .[.first.]. .Iadd.second .Iaddend.outputs     
     
     
        from said plurality of data-receiving means. 15. Process for transferring successive, updated data signals from a source thereof to a plurality of data-signal receivers, each of which indicates its preparedness to receive data signals and which indicates it completed acceptance of applied data signals, the process comprising the steps of: applying the data signals in common to all of the plurality of data-signal receivers from the source;   terminating the application of the data signals in common to all of the plurality of data-signal receivers only in response to all of the plurality of receivers indicating their completed acceptance of the applied data signals; and   controlling the source to apply successive, updated data signals in common to all of the plurality of data-signal receivers only in response to all of the plurality of receivers indicating their preparedness to receive   
     
     
        data signals. 16. Process according to claim 15 wherein the source indicates its completion of the updating to successive data signals, the process comprising the additional steps of: activating all of the plurality of data-signal receivers to receive the updated, successive data signals in common from the source only in response to the indication therefrom of completion of the updating to the successive data signals; and   terminating the indication by the source of its completion of the updating in response to all of the plurality of data-signal receivers indicating   
     
     
        their acceptance of the applied data signals. 17. Process as in claim 16 comprising the additional step of: producing an error indication in response to the simultaneous presence of indications that the data-signal receivers are prepared to receive data signals and have completed acceptance of applied data signals. .Iadd. 18. Process for transferring data signals from a source thereof to a plurality of data receivers, each of which is enableable to receive applied data signals in response to a control signal and which indicates its preparedness to receive data signals and also which indicates its completed acceptance of applied data signals, the process comprising the steps of:   supplying the data signals in common to all of the data-signal receivers from the source;   applying a control signal to the data-signal receivers to enable them to receive the data signals from the source after all of the data-signal receivers indicate their preparedness to receive data signals;   terminating the control signal to disable the data-signal receivers from receiving the data signals after all of the data-signal receivers indicate their completed acceptance of the data signals; and   activating the source to supply successive data signals in common to all of the data-signal receivers after all of the data-signal receivers indicate their completed acceptance of the data signals. .Iaddend..Iadd. 19. Process as in claim 18 wherein in the step of applying, the control signal is applied to the data-signal receivers after all the data-signal receivers indicate their preparedness to receive the data signals and after a selected delay period following the supplying of data signals, which delay period is sufficient to allow reflections and transients in the steady-state data signals to decay away. .Iaddend. .Iadd. 20. Process for transferring successive, updated data signals from a source thereof to a plurality of data receivers, each of which is enableable to receive applied data signals in response to a control signal and which indicates its preparedness to receive data signals and also which indicates its completed acceptance of applied data signals, the process comprising the steps of:   supplying the data signals in common to all of the data-signal receivers from the source;   applying a control signal to the data-signal receivers to enable them to receive the data signals from the source after all of the data-signal receivers indicate their preparedness to receive data signals;   restoring all the data-signal receivers to a condition indicative of not being prepared to receive data signals in response to the application of the control signal thereto;   terminating the control signal to disable the data-signal receivers from receiving the data signals after all of the data-signal receivers indicate their completed acceptance of the data signals;   restoring all the data-signal receivers to a condition indicative of not having completed acceptance of applied data signals after termination of the control signal;   actuating all the data-signal receivers to a condition indicative of being prepared to receive data signals after all the data-signal receivers indicate the condition of not having completed acceptance of applied data signals; and   activating the source to supply successive data signals in common to all of the data-signal receivers after all of the data-signal receivers indicate their completed acceptance of the data signals. .Iaddend. .Iadd. 21. Process as in claim 20 wherein in the step of applying, the control signal is applied to the data-signal receivers after all the data-signal receivers indicate their preparedness to receive the data signals and after a selected delay period following the supplying of data signals, which delay period is sufficient to allow reflections and transients in the steady-state data signals to decay away. .Iaddend.