US 6,587,815 B1Granted

Windowing scheme for analyzing noise from multiple sources

AssigneeSun Microsystems, Inc.

InventorsKathirgamar Aingaran, Manjunath D. Haritsa, Lakshminarasimhan Varadadesikan

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Abstract

Method and apparatus for detecting and analyzing effects of noise in a digital circuit that arises from a coupling of signals produced by switching of a first gate and a second gate in a timed relationship. Where each of a first gate and a second gate can switch within a selected switching time interval, the gate switching effects are combined and the second gate output signal is analyzed with reference to the first gate input signal. Otherwise, the gate switching effects are not combined. When the second gate output signal satisfies at least one of three criteria, this condition is interpreted as indicating that the second gate permits propagation of a noise pulse produced at the first gate.

Claims35

Dependent claims

A method for detecting and analyzing effects of noise in a digital circuit, the method comprising:

providing M selected circuits, numbered m′=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M≧2;
providing a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N≧4, where each group of three consecutive window intervals, referred to as a window group interval, includes at least one of the following time intervals:
an estimated time interval Δt(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 0<xi≦100 (i=1, 2);
an estimated time interval Δt(arrival) of uncertainty in arrival of a voltage input signal V1,in(t) at the at least one gate in the first circuit, and an estimated time interval Δt(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit;
introducing the voltage input signal, V1,in(t), into the first circuit within a selected window interval, allowing the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and estimating a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t);
computing a combined voltage output signal Vc,out(t) as a sum of the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time interval TIm lies within the selected window group interval;
determining whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely
max{Vc,out(t)}≧VN,prop,max,1=max{V1,in(t)}−{margin}, (1)
max{Vc,out(t)}≧VN,prop,max,c=χ·Vdd, (2)
and
∫{Vc,out(t)−Vthr}2dt≧EN,max,Δt(noise) (3)
where {margin} is a selected margin voltage, χ is a selected fraction satisfying 0<χ<1, Vdd is a maximum voltage supplied to at least one of the circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value;
and
when at least one gate in at least one circuit m=2, . . . , M switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit, interpreting this response of the circuits m=2, . . . , M as permitting noise provided at a gate in the first circuit to propagate through at least one gate in at least one of the circuits m=2, . . . , M.

11 more elements

A method for detecting and analyzing effects of noise in a digital circuit, the method comprising:

providing M selected circuits, numbered m′=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M≧2;
providing a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N≧4, where each group of three consecutive window intervals, referred to as a window group interval, includes the following time intervals:
an estimated time interval Δt(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 0<xi≦100 (i=1, 2);
an estimated time interval Δt(arrival) of uncertainty in arrival of a voltage input signal V1,in(t) at the at least one gate in the first circuit, and an estimated time interval Δt(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit;
introducing the voltage input signal, V1,in(t), into the first circuit, within a selected window interval, allowing the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and estimating a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t);
computing a combined voltage output signal Vc,out(t) as a sum of the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time interval TIm lies within for which at least one circuit m=2, . . . , M switches from a first state to a second state lies within the selected window group interval, to form a combined voltage output signal Vc,out(t);
determining whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely
max{Vc,out(t)}≧VN,prop,max,1=max{V1,in(t)}−{margin}, (1)
max{Vc,out(t)}≧VN,prop,max,c=χ·Vdd, (2)
and
∫{Vc,out(t)−Vthr}2dt≧EN,max,Δt(noise) (3)
where {margin} is a selected margin voltage, χ is a selected fraction satisfying 0<χ<1, Vdd is a maximum voltage supplied to at least one of the first and second circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value;
and
when the at least one gate in the second circuit switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit, interpreting this response of the second circuit as permitting noise provided at a gate in the first circuit to propagate through at least one gate in the second circuit.

11 more elements

A system for detecting and analyzing effects of noise in a digital circuit, the system comprising a computer that is programmed:

to provide a representation for M selected circuits, numbered m′=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M is a selected integer that is at least two;
to provide a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N≧4, where each group of three consecutive window intervals, referred to as a window group interval, includes at least one of the following time intervals:
an estimated time interval Δt(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 0<xi≦100 (i=1, 2);
an estimated time interval Δt(arrival) of uncertainty in arrival of a voltage input signal V1,in(t) at the at least one gate in the first circuit, and an estimated time interval Δt(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit;
to simulate introduction the voltage input signal, V1,in(t), into the first circuit within a selected window interval, to allow the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and to estimate a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t);
to add the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time for which at least one circuit m=2, . . . , M switches from a first state to a second state lies within the selected window group interval, to form a combined voltage output signal Vc,out(t);
to determine whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely
max{Vc,out(t)}≧VN,prop,max,1=max{V1,in(t)}−{margin}, (1)
max{Vc,out(t)}≧VN,prop,max,c=χ·Vdd, (2)
and
∫{Vc,out(t)−Vthr}2dt≧EN,max,Δt(noise) (3)
where {margin} is a selected margin voltage, χ is a selected fraction satisfying 0<χ<1, Vdd is a maximum voltage supplied to at least one of the first and second circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value;
and
when the at least one gate in the second circuit switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit, to interpret this response of the second circuit as permitting noise provided at a gate in the first circuit to propagate through at least one gate in the second circuit.

11 more elements

A system for detecting and analyzing effects of noise in a digital circuit, the system comprising a computer that is programmed:

to provide a representation for M selected circuits, numbered m′=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M is a selected integer that is at least two;
to provide a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N≧4, where each group of three consecutive window intervals, referred to as a window group interval, includes the following time intervals:
an estimated time interval Δt(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 0<xi≦100 (i=1, 2);
an estimated time interval Δt(arrival) of uncertainty in arrival of a voltage input signal V1,in(t) at the at least one gate in the first circuit, and an estimated time interval Δt(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit;
to simulate introduction the voltage input signal, V1,in(t), into the first circuit within a selected window interval, to allow the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and to estimate a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t);
to add the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time for which at least one circuit m=2, . . . , M switches from a first state to a second state lies within the selected window group interval, to form a combined voltage output signal Vc,out(t);
to determine whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely
max{Vc,out(t)}≧VN,prop,max,1=max{V1,in(t)}−{margin}, (1)
max{Vc,out(t)}≧VN,prop,max,c=χ·Vdd, (2)
and
∫{Vc,out(t)−Vthr}2dt≧EN,max,Δt(noise) (3)
where {margin} is a selected margin voltage, χ is a selected fraction satisfying 0<χ<1, Vdd is a maximum voltage supplied to at least one of the first and second circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value;
and
when the at least one gate in the second circuit switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit, to interpret this response of the second circuit as permitting noise provided at a gate in the first circuit to propagate through at least one gate in the second circuit.

11 more elements

An article of manufacture comprising:

a computer usable medium having computer readable code means embodied therein for representing M selected circuits, numbered m′=1, 2, . . . , M, that are electrically connected together, each circuit having at least one semiconductor gate, where M is a selected integer that is at least two;
computer readable program code means for providing a wraparound sequence of N consecutive window intervals of selected temporal lengths, with N≧4, where each group of three consecutive window intervals, referred to as a window group interval, includes at least one of the following time intervals:
an estimated time interval Δt(pulse) required for a second circuit to switch from within x1 percent of a second circuit initial voltage value to within x2 percent of a second circuit final voltage value, in response to switching of a first circuit, where x1 and x2 are selected numbers satisfying 0<xi≦100 (i=1, 2);
an estimated time interval Δt(arrival) of uncertainty in arrival of a voltage input signal V1,in(t) at the at least one gate in the first circuit, and an estimated time interval Δt(skew) for uncertainty in accuracy in time provided by a clock signal used to synchronize time for at least one circuit;
computer readable program code means for representing introduction of the voltage input signal, V1,in(t), into the first circuit within a selected window interval, for allowing the at least one gate in the first circuit to switch from a first state to a second state within a selected window group interval, and for estimating a time interval TIm, beginning at the time the input signal V1,in(t) is introduced, within which at least one gate of a circuit numbered m=2, . . . , M switches from a circuit m first state to a circuit m second state and produces a voltage output signal, denoted Vm,out(t);
computer readable program code means for adding the output voltage signals Vm,out(t) (m=2, . . . , M) for which the estimated time for which at least one circuit m=2, . . . , M switches from a first state to a second state lies within the selected window group interval, to form a combined voltage output signal Vc,out(t);
computer readable program code means for determining whether the combined voltage output signal Vc,out(t) satisfies at least one of first, second and third selected noise propagation criteria for the first circuit, namely
max{Vc,out(t)}≧VN,prop,max,1=max{V1,in(t)}−{margin}, (1)
max{Vc,out(t)}≧VN,prop,max,c=χ·Vdd, (2)
and
∫{Vc,out(t)−Vthr}2dt≧EN,max,Δt(noise) (3)
where {margin} is a selected margin voltage, χ is a selected fraction satisfying 0<χ<1, Vdd is a maximum voltage supplied to at least one of the first and second circuits, Vthr is a selected threshold voltage and EN,max is a selected energy value;
and
computer readable program code means for interpreting a selected response of the second circuit as permitting noise provided at a gate in the first circuit to propagate through at least one gate in the second circuit, when the at least one gate in the second circuit switches within the selected window group interval and the combined voltage output signal Vc,out(t) satisfies at least one of the first, second and third noise propagation criteria for the first circuit.

11 more elements

Dependencies are inferred from the claim text.