Real Intent, Inc.

Sun Microsystems, Inc.

Prakash Narain

Christopher F Morrison

Rajeev Kumar Ranjan

John Mark Beardslee

Rajiv Kumar

Vishnu Vimjam

Kevin B Normoyle

Michael A Csoppenszky

Vikas Sachdeva

Sanjeev Mahajan

Paul Vyedin

Oren Katzir

Jay Andrew Littlefield

Methods and systems are described to identify potential failures caused by metastability arising from signal propagation between asynchronous clock domains in integrated circuits with multiple operating modes, each mode allowing selected clocks to propagate. Typical integrated circuits have numerous operating modes, and hence numerous possible clock combinations, each combination causing different asynchronous clock-domain crossings, and hence different potential failures. Since verification for even one clock combination is time-consuming, explicitly enumerating and verifying all possible clock combinations is unviable. In practice very few clock combinations are verified, possibly missing failures. The present invention achieves superior performance, scalability, comprehensiveness and precision in verification despite numerous operating modes, due the following insights: (a) The number of possible clock combinations for a transmit-receive signal pair is small relative to the total number of operating modes, and (b) Cause of failure for a transmit-receive pair remain identical across many clock combinations associated with it.

Methods for identifying integrated circuit failures caused by asynchronous clock-domain crossings in the presence of multiple modes

Integrated circuit failures caused by metastability related to assertion of asynchronous resets frequently escape detection before fabrication, causing design respins and severe economic loss. The numerous reset signals, flip-flops and complex logical interactions inherent in an integrated circuit cause an analysis for reset-metastability failures to be extremely noisy, reporting an unmanageable number of false failures and making early removal of failures impractical. Said noisy reporting arises because many flip-flops where reset-metastability manifests do not necessarily cause overall failure. An effective analysis of reset-metastability failures must identify all potential failures, but also must only report true failure potential. The present invention maximizes noise reduction by applying special conditions to identify flip-flops manifesting reset-metastability without causing integrated circuit failure, which can thereby be deemed safe. By reporting only true failure potential, the present invention enables efficient, robust and error-free removal of reset-related failures from an integrated circuit prior to fabrication.

Methods for identifying integrated circuit failures caused by reset-domain interactions

A method and apparatus are described that facilitate validation of a hardware design having multiple hierarchical levels. In one embodiment, a representation of the hardware design is received, and the hardware design is validated by performing validation processing on a plurality of sub-problems. Each of the plurality of sub-problems covers a computationally feasible size of the hardware design at a corresponding hierarchical level. In another embodiment, validation of a hardware design includes making use of validation processing previously performed with respect to one or more modules included in the hardware design based on the hierarchical relationship between these modules and other modules included in the hardware design.

Hierarchical functional verification

A method and apparatus for characterizing information about design attributes is described. The characterization process may begin with determining the dependency among the attributes within a hardware design. Once the dependency is determined, the most relevant information about the hardware design attribute may be highlighted. A user can then focus their attention on the highlighted aspects of the design attribute to draw conclusions about the hardware design as a whole.

Method and apparatus for characterizing information about design attributes

A method and apparatus are provided that facilitate analysis of the intended flow of logical signals between key points in a design. According to one aspect of the present invention, hardware design defects can be detected using a novel Intent-Driven Verification process. First, a representation of a hardware design and information regarding the intended flow of logical signals among variables in the representation are received. Then, the existence of potential errors in the hardware design may be inferred based upon the information regarding the intended flow of logical signals by (1) translating the information regarding the intended flow of logical signals into a comprehensive set of checks that must hold true in order for the hardware design to operate in accordance with the intended flow of logical signals, and (2) determining if any of the checks can be violated during operation of circuitry represented by the hardware design.

Intent-driven functional verification of digital designs

A method and apparatus are provided that facilitate analysis of the intended flow of logical signals between key points in a design. According to one aspect of the present invention, multiple design verification checks associated with a hardware design are linked by determining dependency reationships among the multiple design verification checks. Each of the design verification checks represent a condition that must hold true in order for the hardware design to operate in accordance with an intended flow of logical signals in the hardware design.

Determining dependency relationships among design verification checks

A method and apparatus are provided that facilitate analysis of the intended flow of logical signals between key points in a design. According to one aspect of the present invention, a comprehensive set of design verification checks may be formulated by applying predetermined properties to an annotated hardware design representation. Information regarding the intended flow of logical signals in the hardware design is received by way of annotations in a control file or annotations embedded in the hardware design representation itself. The annotations include (1) an indication of one or more variables in the representation of the hardware design through which the logical signals pass, and (2) an indication of one or more conditions under which each of the one or more variables are to be associated with each of a set of states. Checks are then automatically formulated based upon a predetermined set of properties that must hold true in order for the hardware design to operate in accordance with the intended flow. Each of the checks is capable of evaluation with reference to the states associated with the one or more variables during propagation of the logical signals.

Automatic formulation of design verification checks based upon a language representation of a hardware design to verify the intended behavior of the hardware design

A method and apparatus are provided that facilitate analysis of the intended flow of logical signals between key points in a design. According to one aspect of the present invention, a method is provided for explicitly associating state information with variables of a language description of a hardware design. Information regarding the intended flow of logical signals among the variables, which represent interconnects in the hardware design through with the logical signals pass, is received. Then, the intended flow of logical signals is modeled by associating state information with the variables in accordance with the intended flow of logical signals. Advantageously, in this manner, the integrity of the data flow can be verified by confirming checks that are expressed as a function of the states associated with the variables.

Modeling and verifying the intended flow of logical signals in a hardware design

A synchronizer comprised in part of a series of flip-flops is used to deterministically transfer data between clock domains during system test. Flip-flops in the clock domain operating at a higher clock frequency have a clock enable signal. The clock enable signal is defined so as to approximately align the enabled rising clock edges of the faster clock signal with the falling edges of the slower clock signal. This approximate alignment provides a timing window of one half period of the slower clock for the data to stabilize at the input of a flip-flop in the faster clock domain before it is sampled. This ensures deterministic transfer of data. Data flow control circuitry can be used to provide a ready signal to the faster clock domain to indicate that the synchronizer is available to transfer a synchronization signal. After testing is complete, the synchronizer can operate in an application mode wherein one or more of the clock enable signals is set to a continuous high level to minimize latency.

Method and apparatus for a testable high frequency synchronizer

A method and structure for testing a circuit with reduced test pattern generation constraints. The circuit includes a first logic circuit coupled to receive input signals from a first flip-flop and a second flip-flop. The first and second flip-flops store part of a test pattern generated to test the circuit. The circuit also includes first and second three state driver (TSD) circuits coupled to receive output signals from the first logic circuit. The output leads of the first and second TSDs are connected to a single input lead of a second logic circuit. The first and second TSDs receive control signals that enable and disable the first and second TSDs. The control signals are provided by the first logic circuit or, alternatively, by a separate decoder. During test operations, the control signals enable the first and second TSDs substantially simultaneously for a predetermined duration. The predetermined duration is short enough to prevent burnout of the first and second TSDs when outputting signals of different logic levels. The predetermined duration is long enough to allow the test pattern to propagate through the second logic circuit and load the output signals of the second logic circuit into third and fourth flip-flops.

Growing community of inventors

San Carlos, CA, United States of America

Prakash Narain