ece667-LSyn7-factored-forms

ece667-LSyn7-factored-forms - ECE 667 Spring 2009 Synthesis...

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1 ECE 667 ECE 667 Spring 2009 Spring 2009 Synthesis and Verification of Digital Systems Multi-level Logic Minimization Multi-level Logic Minimization Factored Forms Factored Forms Slides adopted (with permission) from A. Kuehlmann, UC Berkeley 2003 Slides adopted (with permission) from A. Kuehlmann, UC Berkeley 2003
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2 Outline Outline Factored forms Motivation: multi-level logic representation Definitions, theory, examples Manipulation of Boolean networks Algebraic (structural) vs Boolean methods Decomposition Extraction Factorization Substitution (elimination) Collapsing
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3 General Logic Structure General Logic Structure Combinational optimization (CL blocks) Keep latches/registers at current positions, keep their function Optimize combinational logic domains expressed as multi-level logic – Need efficient representation of multi-level logic
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4 Multi-level Logic Multi-level Logic Logic represented as a network of logic gates from cell library Multi-level logic optimization Logic decomposition and optimization Technology mapping
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5 Optimization Criteria for Synthesis Optimization Criteria for Synthesis The optimization criteria for multi-level logic is to minimize some function of: 1. Area occupied by the logic gates and interconnect (approximated by literals = transistors in technology independent optimization) 2. Critical path delay of the longest path through the logic 3. Degree of testability of the circuit, measured in terms of the percentage of faults covered by a specified set of test vectors for an approximate fault model (e.g. single or multiple stuck-at faults) 4. Power consumed by the logic gates 5. Noise Immunity 6. Physical design constraints
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6 Transformation-based Synthesis Transformation-based Synthesis All modern synthesis systems are build that way – set of transformations that change network representation work on uniform network representation “script” or “scenario” that can combine those transformations to a overall greedy Transformations differ in: – the scope they are applied • local scope versus global restructuring – the domain they optimize combinational versus sequential timing versus area • technology independent versus technology dependent – the underlying algorithms they use • BDD based, SAT based, structure based
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7 Global vs Local Transformations Global vs Local Transformations Global transformations restructure the entire network merging nodes spitting nodes removing/changing connections between nodes, etc. Local transformations optimize the function of one node of the
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ece667-LSyn7-factored-forms - ECE 667 Spring 2009 Synthesis...

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