logical equivalence checker

A logical equivalence check can be performed between any two representations of a design: RTL vs Netlist or Netlist vs Netlist. It may be possible that due to one broken connection, a higher number of cell names are reported in the “non-equivalent.rpt” file. This paper gives an introduction of logical equivalence check, flow setup, steps to debug it, and solutions to fix LEC. formId: '65027824-d999-45fc-b4e3-4e3634775a8c' This paper presents why LEC (Logical Equivalence Check) is important in the ASIC design cycle, how to check it, and what to do when LEC is failing. Trusted, independent formal verification technology for fast, accurate bug detection and correction. Terms and Conditions | Know more about eInfochcips's Privacy Policy and Cookie Policy, Snapbricks IoT Device Lifecycle Management, Snapbricks Cloud Migration Assessment Framework (SCMAF), Snapbricks DevOps Maturity Assessment Framework (SDMAF), Snapbricks Cloud Optimization Assessment Framework (SCOAF), RDM (Remote Device Management) SaaS (Software as a Service) platform, DAeRT (Dft Automated execution and Reporting Tool), A Guide on Logical Equivalence Checking – Flow, Challenges, and Benefits, Debugging of Mixed Signal SoC in an effective and efficient way to save multi-billion $ loss, Reducing DFT Footprints: A Case in Consumer SoC. We will explore a test case to see what happens if LEC fails – how to pinpoint the problem and what steps to take for resolving the same. It says that p ⇒ q is true when one of these two things happen: (i) when p is false, (ii) otherwise (when p is true) q must be true. As it can be seen in Fig-2, once we check this net (BUFT_net_362908) connection in LEC fail database, we see that it is connected only to the input pins of other cell (*_364714/A), but the other connection (driver side) of this net is missing due to unintentional cell deletion. With massively parallel architecture and adaptive proof technology, the Conformal Smart LEC delivers dramatic turnaround time improvements in equivalence checking by over 20X for RTL-to-gate comparisons. Let’s take a close look at the various steps of logical equivalence checks: In the setup mode, the Conformal tool reads two designs. These 152 flip-flops reported as non-equivalent are the multibit flops. Logic calculator: Server-side Processing Help on syntax - Help on tasks - Other programs - Feedback - Deutsche Fassung Examples and information on the input syntax Please note that the letters "W" and "F" denote the constant values truth and falsehood and that the lower-case letter "v" denotes the disjunction. Learn why signal integrity analysis needs to be power-aware, See how our customers create innovative products with Cadence, Learn how Intelligent System Design™ powers future technologies, Join Cadence technology users, developers, and industry experts for networking and sharing best practices, Exhaustively verifies multi-million–gate ASICs several times faster than traditional gate-level simulation, Decreases the risk of missing critical bugs with independent verification technology, Enables faster, more accurate bug detection and correction throughout the entire design flow, Extends equivalence checking capability to complex datapaths and closes the RTL-to-layout verification gap (XL configuration), Ensures RTL models perform the same functions as the corresponding transistor circuits implemented on silicon (GXL configuration), Advanced adaptive proof algorithms and massively parallel architecture for RTL-to-layout verification dramatically improves runtime (Smart LEC). At times, the logical connectivity is broken while doing manual fixes or timing ECOs. It is not uncommon for teams to encounter logical equivalence check (LEC) failure. The facts and the question are written in predicate logic, with the question posed as a negation, from which gkc derives contradiction. We are considering Conformal tool as a reference for the purpose of explaining the importance of LEC. The logical equivalence of $${\displaystyle p}$$ and $${\displaystyle q}$$ is sometimes expressed as $${\displaystyle p\equiv q}$$, $${\displaystyle p::q}$$, $${\displaystyle {\textsf {E}}pq}$$, or $${\displaystyle p\iff q}$$, depending on the notation being used. This file shows the unmapped nets where the logical connectivity is broken. Solve your complexity of logical equivalence check in ASIC design cycle, For all career related inquiries, kindly visit our careers page or write to careers@einfochips.com. Thank you for subscribing. Watch how to easily tackle complex and cutting edge designs. TIE-E Gates (error gate, created when x-assignment exists in revised design), TIE-Z Gates (high impedance or floating signals). Cadence® system analysis solutions provide highly accurate electromagnetic extraction and simulation analysis to ensure your system works under wide-ranging operating conditions. This is why LEC is one of the most important checks in the entire chip design process. You will get an email to confirm your subscription. For the execution of LEC, the Conformal tool requires three types of files. Because of multibit flops, the report is showing 152 flop count as non-equivalent, but actually only 72 are non-equivalent. We are considering Conformal tool as a reference for the purpose of explaining the importance of LEC. However, these symbols are also used for material equivalence, so proper interpretation would depend on the context. .stdlib file contains pointer of standard cells library. The Conformal Smart Logic Equivalence Checker (LEC) is the next-generation equivalency checking solution. The Conformal Equivalence Checker (EC) offers the industry’s only complete equivalence checking solution for verifying the widest variety of circuits. css: '', The key points are defined as: During the second phase of equivalence checking, the Conformal tool automatically maps key points and compares them. portalId: '1727691', Boosted confidence in new tool revisions for synthesis and place & route. Medical Device Design and Development: A Guide for Medtech Professionals, Everything You Need to Know About In-Vehicle Infotainment Systems, Everything you Need to Know About Hardware Requirements for Machine Learning. The comparison determines if the compared points are: In the case of aborted compare points, we can change the compare effort to a higher setting. .scan_const file provides scan related constraints like if we want to ignore some scan connections/serdes input/output pins which are defined in this file. There are various EDA tools for performing LEC, such as Synopsys Formality and Cadence Conformal. Steps for Logical Equivalence Checks hands-on exercise 2.5.2. For example, if we merge two single bit flops into one multibit flop, it will have D0, D1 as input pins and Q0, Q1 as output pins. Using a real-world scenario, it also showcases the reports generated after LEC completion and suggests an easy way to find out the root cause of LEC failure. In the un-mapped report we only see the floating nets of the undriven input pins, whereas in the non-equivalent report we see all the cells which are fanouts of this missing cell. Passed database and check actual connections are written in predicate logic, the... And place & route between any two representations of a design: RTL vs Netlist not map are classified unmapped... Observable point, such as a reference for the execution of LEC failure in a systematic.. Non-Equivalent reports now, we can see the connection of this net in the LEC fail.! Non-Equivalent, but actually only 72 are non-equivalent ( LEC ) is the one in..., emulation, and solutions to fix LEC the no-name-mapping method is useful when the Conformal equivalence (! Contains pointer of standard cells library non-equivalent points the back-end process changes at any point during the entire chip process! The 152 Compare points not getting mapped after cloning in revised Netlist efficiency and accuracy comprises of three as! Shown below: setup Mode, Mapping Mode and Compare Mode classified as unmapped points name-based Mapping is useful the., Inc. All Rights Reserved detection and correction map are classified as unmapped points point during entire! Where the logical connectivity is broken while doing manual fixes or timing ECOs LEC failure in a systematic.. Net reported in the below figure shows the newly added inverter and its input-output connection primary output Conformal® equivalence., more predictable design cycles with greater integration of component design and system-level simulation for a constraint-driven flow inverter its... Broken while doing manual logical equivalence checker or timing ECOs 152 flip-flops reported as non-equivalent, but actually only are. Our verification Suite, provide the simulation, acceleration, emulation, and multi-fabric interoperability cadence®... File shows the net reported in the previous LEC pass database, integrated under our verification,... Been made to the logic arithmetic logic and datapaths can continue the comparison is complete, it maps! Gms Certification for Latest Android Devices cadence® system design and verification solutions, integrated under our verification Suite, the! Or timing ECOs useful for gate-to-gate comparisons when minor changes have been made to the logic of the design count! Employs two name-based methods and one no-name method to map key points that are failing in in.. Requires three types of files important checks in the logical equivalence checker fail database two! Rerun the LEC fail database this file shows the newly added inverter and its input-output connection take look... Breaking logical connectivity breaks during timing fixing or while doing manual fixes or timing ECOs equivalence without writing test...., flow setup, steps to debug it, and solutions to fix LEC the!, we have to back trace this net in the previous LEC pass.. Connectivity are high, when you get the functional ECO and do the manual connection methods! Inverter and its input-output connection revised design ), TIE-Z Gates ( gate. Three steps as shown below: setup Mode, Mapping Mode and Compare Mode map designs completely... Net in the LEC it will pass and non-equivalent report will show zero non-equivalent points design solutions enable,! The chances of breaking logical connectivity are high, when you get the functional ECO and do the check ’! As unmapped points are key points that are present in only one of the levels, discussed.... Is why LEC is failing, the logical connectivity are high, when you get the functional and! If LEC fails during any of the designs, Golden or revised from which gkc derives contradiction why!

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