Hewlett-packard Development Company, L.p.

Hewlett-packard Company

Gerard M Blair

Samuel D Naffziger

James Steven Wells

Eugene Z Berta

What is described is a method to reduce variations in signal delays along paths in a design of an integrated circuit by balancing wire widths. The method operates by performing a circuit simulation to determine simulated signal delays along the circuit paths based on first wire widths for a given circuit, then running a delay model analysis to calculate predicted signal delays along the circuit paths based on first wire widths for the given circuit. The method then calculates a correction difference between the predicted signal delays and the simulated signal delays, and derives delay targets from the correction difference. Finally, the method calculates second wire widths using the delay model analysis to meet the delay targets. Preferably, the signal delays are clock signal delays, the circuit simulation is a SPICE circuit simulation, and the delay model is an Elmore delay model. Also described is a system which includes a CPU and certain memory components for accomplishing the method. Further described is a computer readable medium on which is embedded a program containing the components that execute the described method.

Method to reduce skew in clock signal distribution using balanced wire widths

An arbiter that includes a phase comparator receiving two input signals. The outputs of the phase comparator are propagated to a first SR type flip-flop. The outputs of the first SR type flip-flop are propagated to a second SR type flip-flop. The outputs of the second SR type flip-flop indicate which of the two input. signals changed first. The phase comparator can enter a metastable state. The first flip-flop reduces the magnitude of signal swing away from the power supply rails caused by the metastable state. The second flip-flop prevents any signal swing away for a power supply rail is not propagated to an output.

Arbitrator with no metastable voltage levels on output

A system and method are provided for counting a number of clock cycles. In one embodiment, the system comprises a cascaded series of write latches and a cascaded series of erase latches. The output of each of the write latches is electrically coupled to a respective diverting multiplexer configured to divert a counting signal from the cascaded series of write latches to the cascaded series of erase latches. In order to count a specific number of cycles of the clock, one of the diverting multiplexers is set so as to divert a logical &ldquo;1&rdquo; advancing along the write latches into the erase latches. A specific number of clock cycles is counted by forcing a logical &ldquo;1&rdquo; to advance through a predetermined number of write and erase latches. Generally, the number of write and erase latches used to count a given number of clock cycles is even. Consequently, the present invention also includes an odd latch to enable the counting of an odd number of clock cycles. Also, a number of reset signal pathways are employed to reset the write latches as the logical &ldquo;1&rdquo; is advanced along the erase latches.

System for counting a number of clock cycles such that a count signal is diverted from a cascaded series of write latches to a cascaded series of erase latches

A system and method for actively deskewing synchronous clocks in a VLSI circuit by introducing a controllable delay unit within a local clock buffer within each of a number of circuit zones and applying a controllable delay at each of the local clock buffers in response to a phase comparison of clock signals from one or more adjacent clock zones. The system can be added to any of a number of various clock distribution networks on a VLSI circuit through the introduction of controllable clock zone buffers and localized phase comparators. By adjusting each localized clock buffer delay unit in response to measured clock signal phase differences from adjacent circuit zones, clock skew problems can be minimized across various clock zones on a VLSI circuit.

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Fort Collins, CO, United States of America

Gerard M Blair