Digital Equipment Corporation

Robert Dickson

W Hugh Durdan

George M Uhler

William J Bowhill

A method for synchronizing data transfers in a data processing system is presented. The invention includes two separate clocks generated by a slave processor, one of which is used to synchronize outgoing signals from the communicating elements and the second of which is used to synchronize incoming signals to the communicating elements.

Efficient protocol for communicating between asychronous devices

A protocol for transferring instructions between asynchronous processors in a computer system is provided. Each instruction transfer requires the transfer of an opcode and a variable number of operands. The transfer is accomplished via a bus which interconnects the processors. The opcode and operands are assembled in a buffer in the sending processor and then transferred to the receiving processor in reverse order, i.e., operands first and opcode last. The receiving processor does not acknowledge any of the transfers until it receives the opcode which is always sent last. Upon receipt of the opcode, the receiving processor knows the instruction transfer is complete and sends the acknowledge signal immediately thereafter.

Method and apparatus for optimizing inter-processor instruction transfers

A digital data processing system transfers information with an external device through an interconnect unit over a bus which includes separate sets of lines for transferring control information and transferring user information. The user information lines include bidirectional information transfer lines and undirectional antiparallel lines for transferring direction control signals and synchronization signals between the interconect unit and the external device, the direction control signals indentifying the direction of transfer over the information transfer lines, and the synchronization signals identifying when the transmitting unit has transmitted the signals and when the receiving unit has latched the signals. The control information lines include unidrectional antiparallel lines for transferring control information and a synchronization signal. The synchronization signal is transmitted when control information signals are being transmitted on the control information lines.

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Arlington, MA, United States of America

Robert Dickson