Amdahl Corporation

Cisco Technology, Inc.

Eddie B Collins

James P Millar

Leo Dumov

Ronald D Weber

Clifford A Petersen

A method and system for updating registers by performing an atomic read-modify-write operations initiated by a host over a host/daughtercard bus. A field in the write command determines whether data included in the write command is written to a targeted register or used as a mask to set or clear selected bits in a word held in the targeted register.

Method and system for replacing a read-modify-write operation with an atomic set-bits or clear-bits operation

The invention provides a method and apparatus for immediate control communications between supervising and main processor units. A method in accordance with the invention comprises the steps of: providing a communications memory means within a first clocked system (main system); providing a protocol means within the first clocked system (main system) for indicating various communications states; providing a scan interface, operatively coupled to the communications memory means and the protocol means, for interrogating the state of the protocol means and for scanning data into or out of the communications memory means within a first clocked system (main system); coupling an external second system (SVP) by way of the scan interface to the protocol means and the communications memory means; operating the protocol means so as to indicate to the external second system (SVP) when it is permissible for the second system (SVP) to scan data into or out of the communications memory means; and further operating the protocol means so as to indicate to the first clocked system (main system) whether and/or when the external second system (SVP) has scanned data into or out of the communications memory means.

System having main unit for shutting off clocks to memory upon

Determinism is maintained in a synchronous first system although the first system receives behaviorchanging signals from a second system running asynchronously relative to the first system. The second system refrains from sending behavior-changing signals to the first system until the first system stops its clock at a prespecified clock cycle and signals the second system of the event. The second system then downloads the behavior-changing signals into the first system and restarts the first system clock. The first system awakens to discover that the behavior-changing signals have been received during the prespecified clock cycle. This is repeated over multiple runs, and in each run the same behavior-changing signals are transferred at the same prespecified clock cycles of the first system. Deterministic behavior is thereby maintained in the first system.

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San Jose, CA, United States of America

Eddie B Collins