Statistical timing analysis is an area of growing importance in nanometer te- nologies‚ as the uncertainties associated with process and environmental var- tions increase‚ and this chapter has captured some of the major efforts in this area. This remains a very active field of research‚ and there is likely to be a great deal of new research to be found in conferences and journals after this book is published. In addition to the statistical analysis of combinational circuits‚ a good deal of work has been carried out in analyzing the effect of variations on clock skew. Although we will not treat this subject in this book‚ the reader is referred to [LNPS00‚ HN01‚ JH01‚ ABZ03a] for details. 7 TIMING ANALYSIS FOR SEQUENTIAL CIRCUITS 7.1 INTRODUCTION A general sequential circuit is a network of computational nodes (gates) and memory elements (registers). The computational nodes may be conceptualized as being clustered together in an acyclic network of gates that forms a c- binational logic circuit. A cyclic path in the direction of signal propagation 1 is permitted in the sequential circuit only if it contains at least one register . In general, it is possible to represent any sequential circuit in terms of the schematic shown in Figure 7.1, which has I inputs, O outputs and M registers. The registers outputs feed into the combinational logic which, in turn, feeds the register inputs. Thus, the combinational logic has I + M inputs and O + M outputs.
This volume provides a complete understanding of the fundamental causes of routing congestion in present-day and next-generation VLSI circuits, offers techniques for estimating and relieving congestion, and provides a critical analysis of the accuracy and effectiveness of these techniques. The book includes metrics and optimization techniques for routing congestion at various stages of the VLSI design flow. The subjects covered include an explanation of why the problem of congestion is important and how it will trend, plus definitions of metrics that are appropriate for measuring congestion, and descriptions of techniques for estimating and optimizing routing congestion issues in cell-/library-based VLSI circuits.
This book describes new and effective methodologies for modeling, analyzing and mitigating cell-internal signal electromigration in nanoCMOS, with significant circuit lifetime improvements and no impact on performance, area and power. The authors are the first to analyze and propose a solution for the electromigration effects inside logic cells of a circuit. They show in this book that an interconnect inside a cell can fail reducing considerably the circuit lifetime and they demonstrate a methodology to optimize the lifetime of circuits, by placing the output, Vdd and Vss pin of the cells in the less critical regions, where the electromigration effects are reduced. Readers will be enabled to apply this methodology only for the critical cells in the circuit, avoiding impact in the circuit delay, area and performance, thus increasing the lifetime of the circuit without loss in other characteristics.
Recent years have seen rapid strides in the level of sophistication of VLSI circuits. On the performance front, there is a vital need for techniques to design fast, low-power chips with minimum area for increasingly complex systems, while on the economic side there is the vastly increased pressure of time-to-market. These pressures have made the use of CAD tools mandatory in designing complex systems. Timing Analysis and Optimization of Sequential Circuits describes CAD algorithms for analyzing and optimizing the timing behavior of sequential circuits with special reference to performance parameters such as power and area. A unified approach to performance analysis and optimization of sequential circuits is presented. The state of the art in timing analysis and optimization techniques is described for circuits using edge-triggered or level-sensitive memory elements. Specific emphasis is placed on two methods that are true sequential timing optimizations techniques: retiming and clock skew optimization. Timing Analysis and Optimization of Sequential Circuits covers the following topics: Algorithms for sequential timing analysis Fast algorithms for clock skew optimization and their applications Efficient techniques for retiming large sequential circuits Coupling sequential and combinational optimizations. Timing Analysis and Optimization of Sequential Circuits is written for graduate students, researchers and professionals in the area of CAD for VLSI and VLSI circuit design.
This volume provides a complete understanding of the fundamental causes of routing congestion in present-day and next-generation VLSI circuits, offers techniques for estimating and relieving congestion, and provides a critical analysis of the accuracy and effectiveness of these techniques. The book includes metrics and optimization techniques for routing congestion at various stages of the VLSI design flow. The subjects covered include an explanation of why the problem of congestion is important and how it will trend, plus definitions of metrics that are appropriate for measuring congestion, and descriptions of techniques for estimating and optimizing routing congestion issues in cell-/library-based VLSI circuits.
Statistical timing analysis is an area of growing importance in nanometer te- nologies‚ as the uncertainties associated with process and environmental var- tions increase‚ and this chapter has captured some of the major efforts in this area. This remains a very active field of research‚ and there is likely to be a great deal of new research to be found in conferences and journals after this book is published. In addition to the statistical analysis of combinational circuits‚ a good deal of work has been carried out in analyzing the effect of variations on clock skew. Although we will not treat this subject in this book‚ the reader is referred to [LNPS00‚ HN01‚ JH01‚ ABZ03a] for details. 7 TIMING ANALYSIS FOR SEQUENTIAL CIRCUITS 7.1 INTRODUCTION A general sequential circuit is a network of computational nodes (gates) and memory elements (registers). The computational nodes may be conceptualized as being clustered together in an acyclic network of gates that forms a c- binational logic circuit. A cyclic path in the direction of signal propagation 1 is permitted in the sequential circuit only if it contains at least one register . In general, it is possible to represent any sequential circuit in terms of the schematic shown in Figure 7.1, which has I inputs, O outputs and M registers. The registers outputs feed into the combinational logic which, in turn, feeds the register inputs. Thus, the combinational logic has I + M inputs and O + M outputs.
This book serves both as an introduction to computer architecture and as a guide to using a hardware description language (HDL) to design, model and simulate real digital systems. The book starts with an introduction to Verilog - the HDL chosen for the book since it is widely used in industry and straightforward to learn. Next, the instruction set architecture (ISA) for the simple VeSPA (Very Small Processor Architecture) processor is defined - this is a real working device that has been built and tested at the University of Minnesota by the authors. The VeSPA ISA is used throughout the remainder of the book to demonstrate how behavioural and structural models can be developed and intermingled in Verilog. Although Verilog is used throughout, the lessons learned will be equally applicable to other HDLs. Written for senior and graduate students, this book is also an ideal introduction to Verilog for practising engineers.
This book describes new and effective methodologies for modeling, analyzing and mitigating cell-internal signal electromigration in nanoCMOS, with significant circuit lifetime improvements and no impact on performance, area and power. The authors are the first to analyze and propose a solution for the electromigration effects inside logic cells of a circuit. They show in this book that an interconnect inside a cell can fail reducing considerably the circuit lifetime and they demonstrate a methodology to optimize the lifetime of circuits, by placing the output, Vdd and Vss pin of the cells in the less critical regions, where the electromigration effects are reduced. Readers will be enabled to apply this methodology only for the critical cells in the circuit, avoiding impact in the circuit delay, area and performance, thus increasing the lifetime of the circuit without loss in other characteristics.
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