Typically, a formal equivalence checking tool will also indicate with great precision at which point there exists a difference between two representations. This page was last edited on 9 July 2019, at 07:54. Equivalence Checking of Retimed Circuits: Sometimes it is helpful to move logic from one side of a register to another, and this complicates the checking problem. of Electrical Engineering Indian Institute of Technology Bombay, Mumbai viren@ee.iitb.ac.in EE 709: Testing & Verification of VLSI Circuits Lecture – 6 (Jan 17, 2012) Once the logic designers, by simulations and other verification methods, have verified register transfer description, the design is usually converted into a netlist by a logic synthesis tool. In theory, a logic synthesis tool guarantees that the first netlist is logically equivalent to the RTL source code. The register transfer level (RTL) behavior of a digital chip is usually described with a hardware description language, such as Verilog or VHDL. An alternative way to solve this is to formally prove that the RTL code and the netlist synthesized from it have exactly the same behavior in all (relevant) cases. You currently don’t have access to this book, however you After reading this book, readers will be prepared to introduce FV in their organization and effectively deploy FV techniques to increase design and validation productivity. In Chapter 1, we introduce Formal Verification (FV): the use of tools that mathematically analyze the space of possible behaviors of a design, rather than computing results for particular values. Nikhil Sharma, Gagan Hasteer and Venkat Krishnaswamy. Therefore, instead of blindly assuming that no mistakes were made, a verification step is needed to check the logical equivalence of the final version of the netlist to the original description of the design (golden reference model). The classic example is two identical state machines with different encodings for the states. In practice, programs have bugs and it would be a major risk to assume that all steps from RTL through the final tape-out netlist have been performed without error. Formal equivalence is a known ﬁeld of research and the most common application of the method-ology is in checking the correctness of the netlist generated by the design synthesis against the RTL which is synthesized. Throughout every step of a very complex, multi-step procedure, the original functionality and the behavior described by the original code must be maintained. We begin by describing the general concepts and motivations for using FV methods rather than simpler alternatives. This description is the golden reference model that describes in detail which operations will be executed during which clock cycle and by which pieces of hardware. Equivalence Checking Uses Formal Verification − Prove whether a low level implementation matches a high level, or mathematical, specification Verifying Compiler − Maintain the functionality of generated code Version Control − Use previous implementations to maintain the correctness of future implementations Functional Inversion Sequential equivalence checking for RTL models. The initial netlist will usually undergo a number of transformations such as optimization, addition of Design For Test (DFT) structures, etc., before it is used as the basis for the placement of the logic elements into a physical layout. This process is called gate level logic simulation. The two types of formal verification are equivalence checking and model checking. Sequential Equivalence Checking: Sometimes, two machines are completely different at the combinational level, but should give the same outputs if given the same inputs. Building on a basic knowledge of SystemVerilog, this book demystifies FV and presents the practical applications that are bringing it into mainstream design and validation processes at Intel and other companies. Then, in theory, various forms of property checking can ensure they produce the same output. We use cookies to help provide and enhance our service and tailor content and ads. Erik Seligman, Tom Schubert and M V Achutha Kiran Kumar. A formal equivalence check can be performed between any two representations of a design: RTL <> netlist, netlist <> netlist or RTL <> RTL, though the latter is rare compared to the first two. Since this cannot be reduced to a combinational problem, more general techniques are required. The Quartus® II software provides formal verification support for Altera® designs through interfaces with a formal verification EDA tool, the Cadence Encounter Conformal Logic Equivalence Check (LEC) software. Formal equivalence checking process is a part of electronic design automation (EDA), commonly used during the development of digital integrated circuits, to formally prove that two representations of a circuit design exhibit exactly the same behavior. or buy the full version. checking if two well-defined programs that take N inputs and produce M outputs are equivalent: Conceptually, you can turn software into a state machine (that's what the combination of a compiler does, since a computer plus its memory form a very large state machine.) Both golden and revised designs could be in synthesizable HDL or gate-level netlist form. This problem is even harder than sequential equivalence checking, since the outputs of the two programs may appear at different times; but it is possible, and researchers are working on it. Formality Equivalence Checking: Up to 5x faster performance. 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