US20160364518A1

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Publication number: US20160364518A1
Application number: US14/736,357
Authority: US
Inventors: Mithula Madiraju; Rahul M. Rao
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 2015-06-11
Filing date: 2015-06-11
Publication date: 2016-12-15
Anticipated expiration: 2035-06-11
Also published as: US9519746B1

Abstract

A computer implemented method for correcting early mode slack fails in an electronic circuit can include generating a logical description of an electronic circuit having a path from first circuit to a second circuit. The method then include compiling the logical description into a technology specific representation of the circuit. The method may further include determining that the path has an early mode slack fail. The method may be continued by identifying, in response to determining that a second path has a first early mode slack fail, a complex logic gate located in the second path and having an output coupled to the input of the second circuit that can be decomposed into two or more logic gates. The method may then conclude by decomposing, by processor, the complex logic gate into a two or more logic gates to address the early mode slack fail.

Description

BACKGROUND

The present disclosure relates to electronic circuits, and more specifically, to addressing early mode slack fails in electronic circuits by complex book decomposition.

Computer aided design (CAD) software systems can be used in the development (e.g., design, emulation, and simulation) of electrical circuits and electronic systems. These CAD software systems can improve the efficiency of the design and evaluation of electrical systems by allowing engineers to assemble complex circuits by borrowing from established libraries of electrical components.

A given electrical circuit or electronic system may include a number of electrical paths conveying signals between configurations of sequential and combinational logic sub-circuits. One or more of these electrical path may converge at a single endpoint, with the signals conveyed in each path providing inputs to the same sub-circuits at the endpoints. Electric systems can be designed with consideration towards orchestrating the timing and interaction of signals conducted along disparate paths in a circuit and terminating at these endpoints.

SUMMARY

According to embodiments of the present disclosure, a computer implemented method for correcting early mode slack fails in an electronic circuit can include generating a logical description of an electronic circuit having a path from first circuit to a second circuit. The method then include compiling, by a processor, the logical description into a technology specific representation of the electronic circuit. The method may further include determining, by a processor, that a second path in the technology specific representation of the electronic circuit corresponding with the first path has a first early mode slack fail at the second circuit, wherein an early mode slack fail results when an output of the first circuit coupled to an input of the second circuit has an early mode slack below a first threshold value. The method may be continued by identifying, in response to determining that the path has a first early mode slack fail, a complex logic gate located in the second path and having an output coupled to the input of the second circuit, that can be decomposed into two or more logic gates to correct the first early mode slack fail. The method may then conclude by decomposing, by processor, the complex logic gate into a two or more logic gates to address the early mode slack fail.

Embodiments are directed toward a computer system for addressing early mode slack fails in an electronic circuit. The computer system may include one or more computing nodes having a memory and a processor, and a computer readable storage medium of the one or more computing nodes having program instructions embodied therewith, the program instructions executable by the processor to cause the computer system to: generate a logical description of an electronic circuit having a first path from first circuit to a second circuit; compile the logical description into a technology specific representation of the electronic circuit; determine that a second path in the technology specific representation of the electronic circuit corresponding with the first path has a first early mode slack fail at the second circuit, wherein an early mode slack fail results when an output of the first circuit coupled to an input of the second circuit has an early mode slack below a first threshold value; identify, in response to determining, a complex logic gate located in the second path and having an output coupled to the input of the second circuit, that can be decomposed into two or more logic gates; and decompose, by a processor, the complex logic gate into a two or more logic gates to address the early mode slack fail.

Various embodiments are directed toward a computer program product for addressing early mode slack fails in an electronic circuit.

The above summary is not intended to describe each illustrated embodiment or every implementation of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present application are incorporated into, and form part of, the specification. They illustrate embodiments of the present disclosure and, along with the description, serve to explain the principles of the disclosure. The drawings are only illustrative of certain embodiments and do not limit the disclosure.

FIG. 1 depicts a flowchart of a method for correcting early mode slack fails in electronic circuits, according to various embodiments.

FIG. 2 depicts a second flow chart of a method for correcting early mode slack fails in electronic circuits, according to various embodiments.

FIG. 3 depicts a block diagram of a circuit which may have early mode slack fails, according to various embodiments.

FIG. 4 depicts a circuit configured to correct early mode slack fails by complex book decomposition, according to various embodiments.

FIG. 5A depicts a schematic diagram of an electronic logic circuit which may have early mode slack fails, according to various embodiments.

FIG. 5B depicts a schematic diagram of an electronic logic circuit configured to correct early mode slack fails by complex book decomposition, according to various embodiments.

FIG. 6 depicts a block diagram of a circuit design system for correcting early mode slack fails in electronic circuits, according to various embodiments.

FIG. 7 is a block diagram illustrating an embodiment of a computing device that includes a memory and processor for implementing and executing a circuit design system for correcting early mode slack fails in electronic circuits, according to various embodiments.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to electronic circuits, more particular aspects relate to addressing early mode slack fails in electronic circuits by complex book decomposition. While the present disclosure is not necessarily limited to such applications, various aspects of the disclosure may be appreciated through a discussion of various examples using this context.

Embodiments of this disclosure are based on the recognition that the timing of signals arriving at a single endpoint in an electronic system after being conducted along disparate electrical paths can influence the design and a performance of electronic systems. An endpoint may be the outputs of an electronic circuit, or the inputs of a flip-flop. Timing requirements, including those for early and late mode slack, may enable engineers to include these timing considerations in the design of electrical systems. Violation of the timing requirements during the design of electrical systems may result in a failure in one or more aspects of electrical systems.

Various embodiments of the present disclosure are directed towards a method for correcting early mode slack fails (e.g. fast path fails) in electronic systems. The method may include decomposing complex logic gates located in an electrical path having the early mode slack fail into configurations of a plurality constituent logic circuits. The inputs to the constituent logic circuits may be configured to slow down the fast paths by increasing the number of logic stages a signal conducted along the path propagates though before reaching an endpoint. Moreover, the method may address early mode slack fails by adjusting the physical or technology specific characteristics of the decomposed cells (e.g., gate threshold voltage, or device geometry) to further slow the fast paths.

Embodiments of the present disclosure are directed towards a system and a computer program product for implementing the method for addressing early mode slack fails in electronic systems.

As used here in, a component library may be a collection or database of electronic components, related data, and device models available to a computer aided design system (e.g., an electronic circuit design system). The component library may include cells or books representing individual electronic components or complex electronic functions (e.g., complex logic gates). According to some embodiments, a book that represents a complex logic gate (e.g., a logic gate that cannot be performed by a single two-input logic gate) may be decomposed into two or more books or logic gates. Decomposing complex logic gate may include reducing the complex logic gate into a configuration of two or more basic logic gates configured to perform the same function of the complex logic gate.

The design and development of electronic systems can include analyzing the timing behavior of signals propagated along disparate electrical paths. The timing analysis can include accessing a netlist representing and the electronic system, including technology specific timing models of the components of the electronic system, and determining whether the design of the electronic system satisfy given timing requirements. Determining whether a given timing requirement is satisfied may include calculating the arrival times of signals at various endpoints in a circuit, or determining the longest or shortest delays for signals propagating through paths in a circuit or network of sub-circuits (e.g., determining the slowest and fastest paths). The timing analysis of electronic systems having both sequential and combinational logic circuits may consider the early mode and late mode timing behavior of signals propagated in these circuits.

Early mode timing considers whether signals remain stable long enough at an endpoint to be represented in a sequential or combinational logic operation. Early mode timing requirements (e.g., a hold time requirement) can specify the earliest time that a signal is allowed to become unstable at an endpoint following an event associated with a logic operation (e.g., the occurrence of a clock edge). The early mode timing requirement may be stated as a requirement on early mode slack. In embodiments, early mode slack may be a unit of time by which a late arriving first signal (e.g., a late clock) at an endpoint must precede a second signal that goes unstable early at the same endpoint. Stated differently, early mode slack may be the resulting difference when the earliest time a signal is allowed to become unstable at an endpoint (e.g., as defined by a hold time requirement) is subtracted from the earliest time that the same signal may actually become unstable at an endpoint. Represented this way, a negative early mode slack may identify an early mode timing violation (e.g., because a signal becomes unstable before it is fully represented or captured in a logic operation). An early mode timing violation may also be determined by establishing a threshold early mode slack value, and specifying that a violation occurs when early mode slack falls below the threshold.

A path in an electronic circuit may have an early mode slack fail when one or more circuits in the path have early mode violations. In embodiments, addressing early mode slack fails may include correcting (e.g. removing) early mode violations in a path, or increasing early mode slack to a desired value.

Late mode timing considers whether signals arriving at an endpoint become stable in time to be represented in a logic operation. Late mode timing requirements (e.g., a setup time requirement) can specify the latest time a signal is allowed become stable at an endpoint before an event in a logic operation. The late mode timing requirement may be stated as a requirement on late mode slack. In embodiments, late mode slack may be a unit of time for which a first signal arriving late an endpoint (e.g., a late data) must be stable before a second early arriving signal (e.g., an early clock) reaches the endpoint. Stated differently, late mode slack may be the resulting difference when the latest a signal can become stable at an endpoint is subtracted from the latest a signal is allowed become stable at an endpoint. Represented this way, a negative late mode slack may identify a late mode timing violation (e.g., because the clock signal arrives too early at an endpoint). A late mode timing violation may be determined by establishing a threshold late mode slack value, and specifying that a violation occurs when late mode slack falls below the threshold.

Referring now to the figures,FIG. 1 depicts a flowchart of amethod100 for correcting early mode slack fails in electronic circuits, according to various embodiments. Themethod100 may be automatically carried out by a script controlling a circuit design computing system having one or more software applications, including associated modules and libraries, executing on a processor of computing device such ascomputing device700 described inFIG. 7 infra. Themethod100 may begin atoperation105 when the script loads the circuit design system into a memory of a computing device. Loading the circuit design system may include accessing and loading library components, and a series of circuit design and analysis modules (described infra) in at memory of a computing device. The remaining operations may carried out by the circuit design system on behalf of or in conjunction with the script.

The circuit design system may continue themethod100 by performingoperation110, generating a logical description of an electronic circuit having a path (e.g., an electrical path) from a first circuit to a second circuit. An electronic circuit may be an electronic system or digital circuit having combinational and/or sequential logic components (e.g., combination logic gates such as AND and OR gates, and sequential devices such as clocked flip-flops and synchronous latches). The combinational logic components may include basic and complex logic gates for various functions (e.g., AND, NAND, OR, and XOR gates). Each component of the electronic circuit may be a supplied from a component library consisting of basic cells and complex cells. A complex logic cell may be a logic cell having a logic function that cannot be performed by a single two-input logic cell.

The logical description of the electronic circuit may include a representation of the electronic circuit indicating the interconnection of disparate logic components having inputs and outputs, and describing the electrical paths for conducting signals between the logic components. The logical description may also include logical and mathematical expressions representing each component of the electronic circuit along with their associated interconnections. In some embodiments, a circuit design module of the circuit design system may automatically generate the logical description by reading an electronic file containing a description of the circuit and selecting cells or books from a component library to use in the generation of the logical description.

The circuit design system may continue themethod100 atoperation115 by compiling the logical description of the electronic circuit into a technology specific representation of the circuit. Electronic circuit manufacturing technologies may vary according to, inter alia, the physical processes (e.g., materials used to construct devices, and semiconductor doping levels) used in constructing components, the device geometries of components and interconnects, timing requirements, and the operating and threshold voltages of devices. The circuit design system may direct a compiling module to compile a technology specific representation of the electronic circuit by drawing from a library of technologic specific resources, including data containing timing information, and formulas representing, inter alia, propagation delays through components and interconnects. In some embodiments, a technological specific representation of an electronic circuit may be an electronic representation of an electronic circuit having information relating to the implementation of the electronic using a specific manufacturing technology. The resulting technology specific representation of the electronic circuit may include information, such as timing requirements and device models, to enable a timing analysis to be performed on the electronic circuit.

The circuit design system may continue themethod100 by performingoperation120, determining that a path in the electronic circuit has an early mode slack fail. According to various embodiments, an electrical path from a first sub-circuit (e.g., a first circuit) to a second sub-circuit (e.g., a second circuit) may have an early mode slack fail if at least one logic circuit in the path, situated between the first sub-circuit and the second sub-circuit and having an input coupled to the second circuit, has an early mode violation. In some embodiments, an early mode slack violation may result when an input to the at least one logic circuit has a negative early mode slack, or has an early mode slack that is below a threshold value. The circuit design system may direct a circuit analysis module to calculate the early mode slack at the inputs of each logic circuit in an electrical path having an early mode fail using the formula described previously herein. Additionally, the circuit design module may obtain technology specific requirements on early mode arrival times, including threshold values for early mode slack from a technology specific component library, or from the technology specific representation of the electronic circuit compiled inoperation115. In some embodiments, an early mode slack fail may result in two or more logic operations being performed incorrectly due to, inter alia, signals violating timing requirements at the inputs of logic components.

The circuit design system may continue themethod100 atoperation125 by identifying a complex logic gate, located between a first sub-circuit and a second sub-circuit in a path having an early mode fail and having an input coupled to the second sub-circuit, that can be decomposed to address the early mode slack fail. A complex logic gate may be a logic gate having a logic function that cannot be performed by a single two-input logic gate. The complex logic gate may be suitable for decomposition if a configuration of two or more constituent logic gates can represent or perform the logic function of the complex logic gate. In certain embodiments, a complex logic gate that is suitable for decomposition may have at least one input having early mode violations. In some embodiments, a complex logic gate is suitable for decomposition if at least two inputs have early mode violations. In particular embodiments, the number of inputs of a complex logic gate having early mode violations may be less than the total number of inputs of the complex logic gate. Additionally, when multiple complex logic gates satisfy the above criteria, the complex logic gate having the greatest difference between late mode and early mode arrival times at an endpoint may be selected for decomposition.

In some embodiments, identifying a complex logic gate for decomposition may include the added requirement that the identified gate have some positive late mode slack on each input.

In other embodiments, identifying a complex logic gate for decomposition may include identifying at least two complex logic gates in the path having an early mode slack fail and determining the difference between late and early mode arrival times for each of the at least two complex logic gates (e.g., identify a first complex logic gate having a first difference between early mode and late mode arrival times, and a second complex logic gate having second difference between late mode and early mode arrival times. In some embodiments, the difference between late and early mode arrival may be determined for a given input (e.g., the difference may be determined using the both the late and early mode arrival times of a single input of a complex logic gate). In other embodiments, the difference between late and early mode arrival times may be determined across inputs of a complex logic gate (e.g., the difference may be determined using the late mode arrival time of a first input and the early mode arrival time of a second input of the complex logic gate). The complex logic gate having the greatest difference between early and late mode arrival times may then be selected for decomposition.

The circuit design system may continue themethod100 by performingoperation130, decomposing the complex logic gate identified inoperation125 into two or more logic gates (e.g., constituent logic gates) to address the early mode slack fail. The circuit design system may decompose the complex logic gate by replacing the complex logic gate with two or more constituent logic gates configured to perform the same function of the complex logic gate. In some embodiments, the circuit design system may decompose the complex logic gate to provide an input having an early mode violation a longer path (e.g., a path through multiple logic states) though the two or more constituent logic gates, while providing an input with negative or less positive late mode slack a shorter path through the two or more logic gates. In certain embodiments, two or more logic functions (e.g., a NOT or invert function) may be inserted into at least the path of an input having an early mode violation to further mitigate the early mode slack fail.

According to certain embodiments, the circuit design system may extend thedecomposition operation125 by detuning the two or more constituent logic gates. Detuning the two or more constituent logic gates may include reducing the geometry or size of the gates (e.g. selecting gates from the component library having smaller dimensions). Detuning the two or more constituent logic gates may also include increasing the threshold voltages of the gates (e.g., performing a threshold voltage swap). In certain embodiments, detuning the two or more logic gates may increase early mode slack by, for example, increase the switching times of the gates, or by extending the propagations delays though the gates.

The circuit design system may end themethod100 atoperation135 when the early mode fails are addressed as described herein. However, when the early mode slack fails have not be not been adequately addressed, the circuit design system may continue themethod100 by either returning tooperation120 and identifying an new path having early mode slack fails, or by returning tooperation125 and identifying another complex logic gate that can be decomposed.

FIG. 2 depicts a second flow chart of amethod200 for correcting early mode slack fails in electronic circuits, according to various embodiments. Themethod200 may be automatically carried out by a script controlling a circuit design computing system having one or more software applications, including associated modules and libraries, executing on a processor of computing device such as computing device described inFIG. 7 infra. Themethod200 may begin atoperation205 when the script loads the circuit design system into a memory of the computing device. Loading the circuit design system may include accessing and loading library components, and a series of circuit design and analysis modules (described infra) into a memory of the computing device. Loading the circuit design system may also include generating or accessing a logic description of an electronic circuit and compiling the logic description into a technology specific representation of the electronic circuit, as described in

operations

110 and115 of themethod100. Some aspects ofmethod200 may be an equivalent of embodiment of themethod100 beginning atoperation120 of themethod100. The operations of themethod200 may carried out by the circuit design system on behalf of or in conjunction with the script.

The circuit design system may continue themethod200 atoperation210 by selecting a new path having an early mode slack fail. During a first iteration of themethod200, selecting a new path having an early mode slack fail may include identifying one or more electrical paths in a technology specific representation of the electronic circuit having early mode slack fails—where a path with an early mode slack fail can be identified as discussed inoperation120 of themethod100—and selecting one of the identified paths. During a subsequent iteration of themethod200, the circuit design system may select a second one of the identified paths that was not analyzed during a previous iteration of themethod200.

The circuit design system may then proceed tooperation215 and determine whether there is a complex logic gate that can be decomposed to address the early mode slack fail associated with the selected path. A complex logic gate that may be decomposed to address the early mode slack fail may be identified as discussed inoperation125 of themethod100. The circuit design system may return tooperation210 and select a new path to analyze when a suitable complex logic gate cannot be identified. Alternatively, the circuit design system may continue tooperation220 when it identifies a suitable complex logic gate.

Atoperation220, the circuit design system may determine whether the complex logic gate has at least one input with an early mode violation. The circuit design system may determine that an input has an early mode violation by, for example, determining that the early mode arrival time of a signal at an input of the selected complex logic gate is earlier (e.g. faster) than the allowed early mode arrival time for the signal at the input (e.g., early mode slack is negative or below a technology specific threshold value). The allowed early mode arrival time may be determined by technology specific characteristics of the electronic circuit as discussed herein.

In some embodiments, when the complex gate does not have at least one input with an early mode violation, the circuit design system may continue tooperation225 and mark the complex logic gate as unsuitable for decomposition. The circuit design system may then return tooperation215 and identify another complex logic gate for decomposition.

The circuit design system may continue themethod200 atoperation230 when it determines, atoperation220, that the identified complex logic gate has at least one input with an early mode violation. Atoperation230, the circuit design system may decompose the complex logic gate into one or more constituent logic gates (e.g., basic logic gates). The complex logic gate may be decomposed according to the techniques as discussed inoperation130 of themethod100.

Subsequent to decomposing the complex logic gate, the circuit design system may continue themethod200 atoperation235 by determining whether timing checks are satisfied for the electronic circuit as modified. Determining that timing checks are satisfied may include determining that restrictions on late mode arrival times and late mode slack are not being violated. Additionally, determining that timing check checks are satisfied may include determining that technology specific electrical timing requirements, including requirements on slew rate and rise times, are not being violated. The circuit design system may discard (e.g., reject) the change to the electronic system (e.g., the substitution of constituent logic gates for the selected complex logic gate) and return tooperation215 when the circuit design system determines that the modified electronic circuit violates one or more timing checks. Alternatively, the circuit design system may continue tooperation240 when the modified electronic circuit does not violate the timing checks.

Atoperation240, the circuit design system may determine whether the early mode slack fails of the selected path were addressed. In some embodiments, determining that the early mode slack fail has been addressed includes determining that the early mode slack at sub-circuit (e.g. a second circuit) at the end of the path has been increased above a threshold value. The threshold value may be a technology specific value determined from a library of technology specific timing values and requirements, as discussed herein.

In some embodiments, themethod200 may end atoperation260 when the circuit design system determines that the early mode fails of the selected path were addressed. In other embodiments, themethod200 may be continued atoperation205 oroperation210 while there are additional paths with early mode slack fails.

The circuit design system may continue themethod200 by performingoperation245 when it determines that the early mode violations for the selected path were not corrected atoperation240. Performingoperation245 can include detuning the two or more constituent logic gates as described in the discussion ofoperation130 of themethod100.

Subsequent to detuning the two or more logic gates, the circuit design system may continue themethod200 atoperation250 by determining whether timing checks are satisfied for the electronic circuit as modified by the detuning. Determining the timing checks are satisfied may be performed as described inoperation235. The circuit design system may discard (e.g., reject) the detuning changes to the electronic circuit, including, for example, the decomposition of the complex logic gate and the detuning, and return tooperation215 when the circuit design system determines that the modified electronic circuit violates the timing checks. The circuit design system may continue tooperation255 when the modified electronic circuit does not violate any timing checks.

Atoperation255, the circuit design system may determine whether the early mode slack fails of the selected path have been addressed, as discussed inoperation240. The circuit design system may continueoperation220 when the early mode slack fails of the selected path have been addressed. Alternatively, the circuit design system may return tooperation215 and identify a new complex logic gate for decomposition when the early mode slack fails of the selected path have not been addressed.

FIG. 3 depicts a block diagram of acircuit300 which may have early mode slack fails, according to various embodiments. Thecircuit300 includes flip-

flops

305,315 and330, combinational logic blocks310,320 and325, and input signals INPUT_A, CLK. The combinational logic blocks310,320, and325 may represent complex combinational logic gates.

Flip-flop315 may receive an input signal fromcombinational logic block310.Combinational logic block310 may provide an input signal to flip-flop315 in response to receiving a first input signal INPUT_A and a second input signal from flip-flop305. For the purposes of this disclosure, INPUT_A can be a signal having a constant value. Flip-flop330 may receive an input signal fromcombinational logic block325.Combinational logic block325 may provide an input signal to flip-flop330 in response to receiving an input signal fromcombinational logic block320.Combinational logic block320 may provide an input signal tocombinational logic block325 in response to receiving an input signal from flip-flop305. Flip-

flops

305,315 and330 may be clocked by the same input signal CLK. The propagation delay (e.g., a combinational logic block delay) of a signal traversing one of the combinational logic blocks (e.g. combinational logic blocks310,320 and325) from an input to an output of the combinational logic block may be the same for each combinational logic block.

Flip-

flops

315 and330 may be part of a register bank and configured to capture inputs received from

combinational logic circuits

310 and325 during each cycle of clock input CLK (e.g., the flip-flops latch the outputs of the combinational logic blocks after being triggered by an edge of CLK). A given technology specific implementation of thecircuit300 may specify a hold time requirement (e.g., a threshold early mode slack value) for the input signals received from combinational logic blocks310 and325. The hold time requirement may specify that the input signals received from combinational logic blocks310 and325 may not go unstable for a threshold amount of time after an edge of CLK is received at flip-

flops

315 and330.

Each cycles of CLK received at flip-flop305 may cause the flip-flop to provide a new signal value to the inputs of combinational logic blocks310 and320. After each cycle of CLK, the new signal value from flip-flop305, as propagated alongPATH301, may take at least one combinational logic block delay to reach the input of flip-flop315. Similarly, the new signal value from flip-flop305, as propagated alongPATH302, may take at least two combinational logic block delays to reach the input of flip-flop330. In some embodiments, two combinational logic block delays may be sufficient to satisfy the hold time requirements (e.g. early mode slack requirements) for thecircuit300, while a one combinational logic block delay may cause a violation of the hold time requirement. Consequently,PATH301 may have an early mode slack fail because the delay in the path is too small (e.g., a signal conducted along the path propagates too fast) to satisfy the hold time requirements of thecircuit300.

FIG. 4 depicts acircuit400 configured to correct early mode slack fails by complex book decomposition, according to various embodiments. Thecircuit400 is an equivalent embodiment of thecircuit300 inFIG. 3, with the exception that the early mode slack violation of thecircuit300 has been addressed by decomposingcombinational logic block310 into a configuration ofconstituent logic gates410 using the methods described herein. The configuration ofconstituent logic gates410 includes constituent logic blocks411,412 and413. The constituent logic blocks411,412,413 each represent discrete logic functions collectively configured to perform the logic function of thecombinational logic block310. Decomposing thecombinational logic block310 into three discrete logic blocks may increase the delay along PATH401 (e.g., the delay inpath410 may be longer the delay ofpath301 in the circuit300) as experienced by a signal propagated from the output of flip-flop305 to the input of flip-flop315. The increased delay inPATH401 may address the early mode slack fail seen in thecircuit300 by increasing the early mode slack of the signal propagated along the path.

FIG. 5A depicts a schematic diagram of anelectronic logic circuit500A which may have early mode slack fails, according to various embodiments. As shown incircuit500A, a 4-input NAND gate535 receives an input from a 3-input NAND gate525 (e.g. a complex logic gate). The 3-input NAND525 provides an input toNAND gate535 in response to receiving inputs from flip-

flops

505 and510, and 2-input ORgate530. In some embodiments, a signal propagated through ORgate530 may experience a longer delay (e.g., a slower path) toNAND gate525 than signals propagated from the outputs of flip-

flops

505 and510. Consequently, thecircuit500A may have early mode violations at the inputs ofNAND gate525 that are coupled to flip-

flops

505 and510. The resulting violations may cause early mode slack rails atNAND gate535.

FIG. 5B depicts a schematic diagram of anelectronic logic circuit500B configured to correct early mode slack fails by complex book decomposition, according to various embodiments. Thecircuit500B may be an embodiment of an electronic circuit equivalent to thecircuit500A with the exception that the early mode slack violations of thecircuit500A are addressed by decomposing the 3-input NAND gate525 of thecircuit500A into two 2-

input NAND gates

510B and525B, andinverter515B.

FIG. 6 depicts a block diagram of acircuit design system600 for correcting early mode slack fails in electronic circuits, according to various embodiments. Thecircuit design system600 may be embodied in a software application stored in the memory of a computing device, and configured to execute on a processor of the computing device. The circuit design system may includecircuit design module605, compilingmodule610,circuit analysis module615,book decomposition module620,detuning module622, andcomponent library625. Collectively, the circuit design system may be embodied in a script or software application configured to automatically interface with, and exchange message, including data, between each module while carrying out the methods of this disclosure.

Thecircuit design module605 may be configured to automatically generate a logical description of an electronic circuit by reading an electronic file containing a description of the circuit (e.g. an electronic schematic) and selecting logic cells or books from thecomponent library625 to use in the generation of the logical description. The circuit design module may provide a file containing the logical description of the electronic circuit to the circuit design system600 (e.g., the file may be provided to a script configured to interface with the components of the circuit design system).

Thecompiling module605 may receive, from the circuit design system (e.g., executing on the behalf of a controlling script), an electronic file having a logical description of an electronic circuit. Thecompiling module605 to may be configured to compile, on the behalf of thecircuit design system600, a technology specific representation of the electronic circuit by drawing from a library of technologic specific resources, including timing data information and formulas representing, inter alia, propagation delays through components and their interconnects (e.g., traces). Thecircuit design module605 may be further configured to provide, to thecircuit design system600, a technology specific representation of the compiled electronic circuit, including information (e.g., timing data, device models, and requirements) to enable a timing analysis of the electronic circuit.

Circuit analysis module

615 may receive, from thecircuit design system600, an electronic file having a compiled technology specific representation of an electronic circuit. Thecircuit analysis module615 may be configured to process the data, models, and requirements contained in the technology specific representation of the electronic circuit and analyze the timing characteristics of the circuit to determine whether one or more paths of the electronic circuit have timing violations, including early mode and late mode timing violations, early mode and late mode slack fails, and electronic time violations as described herein. Thecircuit analysis module615 may provide the results of the timing analysis to thecircuit design system600.

Book decomposition module

620 may receive a complex logic circuit (e.g., a complex book) from the circuit design system for decomposition. The circuit design system may also providedecomposition module620 an indication of which inputs to the complex logic gate have early mode violations. Thedecomposition module620 may be configured to decompose the complex logic circuit by identifying two or more constituent logic gates or books fromcomponent library module625 that can perform the logic function of the complex logic gate. Thedecomposition module620 may be further configured to arrange the two or more constituent logic gates in a configuration that performs the logic function of the complex logic gate. Arranging the two or more constituent gates may include generating a configuration that provides the inputs having early mode violations the longest path through the configuration of two or more constituent logic gates. Thedecomposition module620 may provide a logic or a technology specific representation of the configuration of more or more constituent logic gates or of the modified electronic to thecircuit design system600.

Detuning module

622 may receive a technology specific representation of two or more logic gates from the circuit design system for detuning. The detuning module may involve detuning only one of the two or more gates considered for detuning.Detuning module622 may be configured to detune the logic gates by increasing geometry of the gates (e.g. increase the size of the transistors making up the logic gates), or by increasing the threshold voltage of the gates (e.g., modify the technology specific representation of the gates to specify a higher threshold voltage). Thedetuning module622 may provide a technology specific representation of the two or more logic gates (or the electronic circuit) modified to reflect the detuning tocircuit design system600.

Component library

625 may include cells of basic electronic circuit elements (e.g., basic combinational logic gates, latches, and flip-flops).Library component625 may also include books of more complex logic functions (e.g., complex logic gates). In some embodiments, the component library may include technology specific representations of the logic cells or books, including timing information, physical geometries, and threshold voltages.

FIG. 7 is a block diagram illustrating an embodiment of a computing device that includes a memory and processor for implementing and executing a circuit design system for correcting early mode slack fails in electronic circuits, according to various embodiments. The components of thecomputing device700 can include one ormore processors706, amemory712, aterminal interface718, astorage interface720, an Input/Output (“I/O”)device interface722, and anetwork interface724, all of which are communicatively coupled, directly or indirectly, for inter-component communication via a memory bus710, an I/O bus716, bus interface unit (“IF”)708, and an I/Obus interface unit714.

Thecomputing device700 may include one or more general-purpose programmable central processing units (CPUs)706A and706B, herein generically referred to as theprocessor706. In certain embodiments, a processor may be any electronic device having a datapath for executing a sequence of programmed instructions and capable of performing arithmetic logic computations (e.g., using an arithmetic logic unit), include application specific integrated circuits, and field programmable gate arrays. In an embodiment, thecomputing device700 may contain multiple processors; however, in another embodiment, thecomputing device700 may alternatively be a single CPU device. Eachprocessor706 executes instructions stored in thememory712.

Thecomputing device700 may include abus interface unit708 to handle communications among theprocessor706, thememory712, thedisplay system704, and the I/Obus interface unit714. The I/Obus interface unit714 may be coupled with the I/O bus716 for transferring data to and from the various I/O units. The I/Obus interface unit714 may communicate with multiple I/

O interface units

718,720,722, and724, which are also known as I/O processors (IOPs) or I/O adapters (IOAs), through the I/O bus716. Thedisplay system704 may include a display controller, a display memory, or both. The display controller may provide video, audio, or both types of data to adisplay device702. The display memory may be a dedicated memory for buffering video data. Thedisplay system704 may be coupled with adisplay device702, such as a standalone display screen, computer monitor, television, a tablet or handheld device display, or another other displayable device. In an embodiment, the display device102 may include one or more speakers for rendering audio. Alternatively, one or more speakers for rendering audio may be coupled with an I/O interface unit. In alternate embodiments, one or more functions provided by thedisplay system704 may be on board an integrated circuit that also includes theprocessor706. In addition, one or more of the functions provided by thebus interface unit708 may be on board an integrated circuit that also includes theprocessor706.

The I/O interface units support communication with a variety of storage and I/O devices. For example, theterminal interface unit718 supports the attachment of one or more user I/O devices, which may include user output devices (such as a video display devices, speaker, and/or television set) and user input devices (such as a keyboard, mouse, keypad, touchpad, trackball, buttons, light pen, or other pointing devices). A user may manipulate the user input devices using a user interface, in order to provide input data and commands to the user I/O device726 and thecomputing device700, may receive output data via the user output devices. For example, a user interface may be presented via the user I/O device726, such as displayed on a display device, played via a speaker, or printed via a printer.

Thestorage interface720 supports the attachment of one or more disk drives or direct access storage devices728 (which are typically rotating magnetic disk drive storage devices, although they could alternatively be other storage devices, including arrays of disk drives configured to appear as a single large storage device to a host computer, or solid-state drives, such as a flash memory). In another embodiment, thestorage device728 may be implemented via any type of secondary storage device. The contents of thememory712, or any portion thereof, may be stored to and retrieved from thestorage device728 as needed. The I/O device interface722 provides an interface to any of various other I/O devices or devices of other types, such as printers or fax machines. Thenetwork interface724 provides one or more communication paths from thecomputing device700 to other digital devices and computer systems.

Although thecomputing device700 shown inFIG. 7 illustrates a particular bus structure providing a direct communication path among theprocessors706, thememory712, thebus interface708, thedisplay system704, and the I/Obus interface unit714, in alternative embodiments thecomputing device700 may include different buses or communication paths, which may be arranged in any of various forms, such as point-to-point links in hierarchical, star or web configurations, multiple hierarchical buses, parallel and redundant paths, or any other appropriate type of configuration. Furthermore, while the I/Obus interface unit714 and the I/O bus708 are shown as single respective units, thecomputing device700, may include multiple I/Obus interface units714 and/or multiple I/O buses716. While multiple I/O interface units are shown, which separate the I/O bus716 from various communication paths running to the various I/O devices, in other embodiments, some or all of the I/O devices are connected directly to one or more system I/O buses.

In various embodiments, thecomputing device700 is a multi-user mainframe computer system, a single-user system, or a server computer or similar device that has little or no direct user interface, but receives requests from other computer systems (clients). In other embodiments, thecomputing device700 may be implemented as a desktop computer, portable computer, laptop or notebook computer, tablet computer, pocket computer, telephone, smart phone, or any other suitable type of electronic device.

In an embodiment, thememory712 may include a random-access semiconductor memory, storage device, or storage medium (either volatile or non-volatile) for storing or encoding data and programs. In another embodiment, thememory712 represents the entire virtual memory of thecomputing device700, and may also include the virtual memory of other computer systems coupled to thecomputing device700 or connected via anetwork730. Thememory712 may be a single monolithic entity, but in other embodiments thememory712 may include a hierarchy of caches and other memory devices. For example, memory may exist in multiple levels of caches, and these caches may be further divided by function, so that one cache holds instructions while another holds non-instruction data, which is used by the processor.Memory712 may be further distributed and associated with different CPUs or sets of CPUs, as is known in any various so-called non-uniform memory access (NUMA) computer architectures.

Thememory712 may store all or a portion of the components and data shown inFIGS. 1-6. In particular, thememory712 may store thecircuit design system712A, along with the modules, scripts and library components used to implement the methods of the present disclosure. Thecircuit design system712A may be an equivalent embodiment of thecircuit design system600 shown inFIG. 6. Thememory712 may also include a graphical user interface (GUI)712B for interfacing with thecircuit design system712A. These programs and data structures are illustrated inFIGS. 1-6 as being included within thememory712 in thecomputing device700; however, in other embodiments, some or all of them may be on different computer systems and may be accessed remotely, e.g., via anetwork730. Thecomputing device700 may use virtual addressing mechanisms that allow the programs of thecomputing device700 to behave as if they only have access to a large, single storage entity instead of access to multiple, smaller storage entities. Thus, while the components and data shown inFIGS. 1-6 are illustrated as being included within thememory712, these components and data are not necessarily all completely contained in the same storage device at the same time. Although the components and data shown inFIGS. 1-6 are illustrated as being separate entities, in other embodiments some of them, portions of some of them, or all of them may be packaged together.

In an embodiment, the components and data shown inFIGS. 1-6 may include instructions or statements that execute on theprocessor706 or instructions or statements that are interpreted by instructions or statements that execute theprocessor706 to carry out the functions as further described below. In another embodiment, the components shown inFIGS. 1-6 may be implemented in hardware via semiconductor devices, chips, logical gates, circuits, circuit cards, and/or other physical hardware devices in lieu of, or in addition to, a processor-based system. In an embodiment, the components shown inFIGS. 1-6 may include data in addition to instructions or statements.

FIG. 7 is intended to depict representative components of thecomputing device700. Individual components, however, may have greater complexity than represented inFIG. 7. InFIG. 7, components other than or in addition to those shown may be present, and the number, type, and configuration of such components may vary. Several particular examples of additional complexity or additional variations are disclosed herein; these are by way of example only and are not necessarily the only such variations. The various program components illustrated inFIG. 7 may be implemented, in various embodiments, in a number of different ways, including using various computer applications, routines, components, programs, objects, modules, data structures etc., which may be referred to herein as “software,” “computer programs,” or simply “programs.”

The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.

Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.

These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A computer implemented method for correcting early mode slack fails in an electronic circuit, comprising:

generating a logical description of an electronic circuit having a first path from first circuit to a second circuit;

compiling, by a processor, the logical description into a technology specific representation of the electronic circuit;

determining, by a processor, that a second path in the technology specific representation of the electronic circuit corresponding with the first path has a first early mode slack fail at the second circuit, wherein an early mode slack fail results when an output of the first circuit coupled to an input of the second circuit has an early mode slack below a first threshold value;

identifying, in response to the determining, a complex logic gate located in the second path and having an output coupled to the input of the second circuit, that can be decomposed into two or more logic gates; and

decomposing, by a processor, the complex logic gate into a two or more logic gates to address the early mode slack fail, wherein an electrical signal propagating in the second path to the second circuit though the decomposed complex logic gate traverses at least one logic stage more than an electrical signal propagating in the second path to the second logic circuit though the complex logic gate.

2. The method ofclaim 1, wherein the identifying further includes:

determining that the complex logic gate has at least one input having an early mode timing violation.

3. The method ofclaim 2, further comprising:

determining, subsequent to the decomposing, that the second path has a second early mode slack fail at the second circuit;

detuning, in response to determining that the second path has a second early mode slack fail at the second circuit, the two or more logic gates to increase the early mode slack above the threshold value.

4. The method ofclaim 2, wherein the detuning includes increasing a threshold voltage of one or more transistors in the one or more logic gates.

5. The method ofclaim 2, wherein the detuning includes reducing a drive strength of the one or more logic gates.

6. The method ofclaim 1, wherein the identifying comprises:

identifying, in the second path, a first complex logic gate having a first difference between early mode and late mode arrival times, and a second complex logic gate having second difference between early mode and late mode arrival times;

determining that the first difference is numerically greater than the second difference; and

selecting, in response to determining that the first difference is numerically greater, the first complex logic gate for decomposition.

7. The method ofclaim 1, further comprising:

determining, in response to the decomposing, whether one or more timing checks were violated by the one or more logic gates;

rejecting, in response to determining that one or more timing checks were violated, the decomposition; and

accepting, in response to determining that one or more timing checks were not violated, the decomposition.

8. The method ofclaim 3, further comprising:

determining, in response to the detuning, whether one or more timing checks were violated by the one or more logic gates;

rejecting, in response to determining that one or more timing checks were violated, the detuning; and

accepting, in response to determining that one or more timing checks were not violated, the detuning.

9. A computer system for addressing early mode slack fails in an electronic circuit, comprising:

one or more computing nodes having a memory and a processor; and

a non-transitory computer readable storage medium of the one or more computing nodes having program instructions embodied therewith, the program instructions executable by the processor to cause the computer system to:

generate a logical description of an electronic circuit having a first path from first circuit to a second circuit;

compile the logical description into a technology specific representation of the electronic circuit;

determine that a second path in the technology specific representation of the electronic circuit corresponding with the first path has a first early mode slack fail at the second circuit, wherein an early mode slack fail results when an output of the first circuit coupled to an input of the second circuit has an early mode slack below a first threshold value;

identify, in response to determining, a complex logic gate located in the second path and having an output coupled to the input of the second circuit, that can be decomposed into two or more logic gates; and

decompose, by a processor, the complex logic gate into a two or more logic gates to address the early mode slack fail, wherein an electrical signal propagating in the second path to the second circuit though the decomposed complex logic gate traverses at least one logic stage more than an electrical signal propagating in the second path to the second logic circuit though the complex logic gate.

10. The computer system ofclaim 9, wherein the program instructions executable by the processor further cause the computer system to:

determine that the complex logic gate has at least one input having an early mode timing violation.

11. The computer system ofclaim 10, wherein the program instructions executable by the processor further cause the computer system to:

determine, subsequent to decomposing, that the second path has a second early mode slack fail at the second circuit;

detune, in response to determining that the second path has a second early mode slack fail at the second circuit, the two or more logic gates to increase early mode slack above the threshold value.

12. The computer system ofclaim 10, wherein the program instructions executable by the processor further cause the computer system to:

increase a threshold voltage of one or more transistors in the one or more logic gates.

13. The computer system ofclaim 10, wherein the program instructions executable by the processor further cause the computer system to:

reduce a drive strength of the one or more logic gates.

14. The computer system ofclaim 9, wherein the program instructions executable by the processor further cause the computer system to:

identify, in the second path, a first complex logic gate having a first difference between early mode and late mode arrival times, and a second complex logic gate having second difference between early mode and late mode arrival times;

determine that the first difference is numerically greater than the second difference; and

select, in response to determining that the first difference is numerically greater, the first complex logic gate for decomposition.

15. A computer program product for addressing early mode slack fails in an electronic circuit, the computer program product including a non-transitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processing circuit to cause the processing circuit to perform a method comprising:

16. The computer program product ofclaim 15, wherein the identifying further includes:

17. The computer program product ofclaim 16, further comprising:

18. The computer program product ofclaim 16, wherein the detuning includes increasing a threshold voltage of one or more transistors in the one or more logic gates.

19. The computer program product ofclaim 16, wherein the detuning includes reducing a drive strength of the one or more logic gates.

20. The computer program product ofclaim 1, wherein the identifying comprises:

determining that the first difference is numerically greater than the second difference; and selecting, in response to determining that the first difference is numerically greater, the first complex logic gate for decomposition.