Other

Sun Microsystems, Inc.

Plx Technology, Inc.

James H Ma

Lisa C Grenier

Mark T Kawahigashi

A digital crossbar switch utilizes an asynchronous RAM to provide high density and low latency storage and a write enable pulse generator to generate write enable pulses that are independent of the clock signal duty cycles. The crossbar switch includes a plurality of ports coupled to a bus, at least one memory element coupled to one of the plurality of ports, and a circuit for generating a write enable pulse coupled to each of the memory element. The circuit for generating the write enable pulse includes a pulse generator for generating a pulse, the pulse tracking a leading edge of a clock signal, a write enable signal generator for generating a write enable signal, and a first logic circuit coupled to the pulse generator and the write enable signal generator for generating the write enable pulse by combining the pulse and the write enable signal.

Method and apparatus for implementing low latency crossbar switches with integrated storage signals

A crossbar switch is disclosed. The crossbar switch comprises a plurality of input sorting units and a plurality of merge and interleave units. Each input sorting unit is capable of receiving from a respective device an access request to any one of a plurality of physical memory devices. Each merge and interleave unit is capable of arbitrating among competing access requests received from any of the input sorting units, selecting one of the competing access requests and forwarding the selected request for implementation on a respective memory device. Also disclosed is method implemented by the crossbar switch.

Self-optimizing crossbar switch

Methods and apparatus implementing techniques for prevention of metastability in a bistable circuit. The techniques include detecting a change in a data signal, sampling the detected change in reference to a sampling window of a clock signal input of a bistable circuit to determine if the detected change occurs within the sampling window, and selecting a stable data input to present to an input of the bistable circuit based on whether the detected change occurs within the sampling window. The sampling window represents a time period during which a change in the data signal can cause metastability in a bistable circuit.

Prevention of metastability in bistable circuits

A method and circuit for transferring multiple bits of data across asynchronous clock domains is provided. The method includes detecting a change in a status bit of a data word being transferred from a source in a source clock domain to a destination register in a destination clock domain, the source clock and destination clock being asynchronous. The method includes sampling the detected change in reference to a change window where the change window is sized to encompass all bits of the data word. A stable input is selected for each bistable circuit of the destination register based on whether the detected change in the status bit is likely to produce metastability in the receiving register.

Transfer of digital data across asynchronous clock domains

A technique for arbitrating and selecting one access request to a shared memory from among multiple contenders is disclosed. In a first aspect, the invention includes a method for accessing a shared memory. The method includes receiving a plurality of access requests; presenting a plurality of characteristics for each access request; ascertaining a plurality of operational characteristics; and selecting one of the access requests for processing upon consideration of the access request characteristics and the operational characteristics. In a second aspect, the invention includes an arbitration and select logic (&ldquo;ASL&rdquo;) unit. The ASL unit comprises a plurality of input sorting units, each input sorting unit capable of receiving a respective access request and a merge and interleave unit (&ldquo;MIU&rdquo;). The MIU is capable of receiving a plurality of characteristics for each access request; receiving a plurality of operational characteristics; and selecting one of the access requests for processing upon consideration of the access request characteristics and the operational characteristics.

Arbitration and select logic for accessing a shared memory

A circuit and method for generating a write enable pulse that is independent of the clock duty cycle and the clock frequency. The circuit includes a pulse generator for generating a pulse in response to a clock signal and a write enable signal generator for generating a write enable pulse. The pulse tracks the leading edge of the clock signal. A logic circuit is coupled to the pulse generator and the write enable signal generator to generate the write enable pulse by combining the pulse and the write enable signal.

Method and apparatus for generating and controlling integrated circuit memory write signals

A binary relative delay line device having two delay lines, each of which delays, during a time interval, an input signal by a substantially equal amount of time. Each delay line requires a settling time before it is selected during a next time interval. A selection and delay determining circuit is coupled to the two delay lines to select one of them to provide an output signal. A clock is coupled to the selection and delay determining circuit to operate the selection and delay determining circuit at a lower frequency than the frequency of the input signal, the lower frequency being chosen so that any selected delay line has settled before it is selected.

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San Jose, CA, United States of America

James H Ma