clocking - ECE 6130/4130 Advance VLSI Systems Fall 2009...

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Unformatted text preview: ECE 6130/4130: Advance VLSI Systems Fall 2009 Clocking Prof. Saibal Mukhopadhyay School of Electrical & Computer Engineering Georgia Institute of Technology Reading Materials • Chapter 15 : Introduction to VLSI Circuits and Systems , Uyemura, • Lecture notes (posted in T-square, under “Resources/Lecture Slides”) – Source: Digital Integrated Circuits by Rabaye et. al. • Chapter 10: Digital Integrated Circuits: Rabaye Register Parameters D Clk Q D Q Clk t c-q t hold T t su Delays can be different for rising and falling data transitions Synchronous Timing Combinational Logic R 1 R 2 C in C out Out In CLK t c-q t setup t hold t logic_max T logic_min t CLK1 t CLK2 t c-q t setup t hold Ideally t CLK1 = t CLK2 Minimum CLK Period: T > t c-q + t logic_max + t setup To avoid race condition: t hold < t c-q + t logic_min Clock Uncertainties 2 4 3 Power Supply Interconnect 5 Temperature 6 Capacitive Load 7 Coupling to Adjacent Lines 1 Clock Generation Devices Sources of clock uncertainty Clock Nonidealities • Clock skew – Spatial variation in temporally equivalent clock edges; deterministic + random, t SK • Clock jitter – Temporal variations in consecutive edges of the clock signal; modulation + random noise – Cycle-to-cycle (short-term) t JS – Long term t JL Clock Skew and Jitter • Both skew and jitter affect the effective cycle time Clk Clk t SK t JS Clock Skew # of registers Clk delay Insertion delay Max Clk skew Earliest occurrence of Clk edge Nominal – δ /2 Latest occurrence of Clk edge Nominal + δ /2 δ Positive Skew R 1 In Combinational Logic D Q t CLK1 CLK delay t CLK2 R 2 D Q Combinational Logic t CLK3 R 3 • • • D Q delay Receiving clock edge arrives late Positive Skew CLK1 CLK2 T CLK δ T CLK + δ + t h δ 2 1 4 3 Launching edge arrives before the receiving edge Timing Constraints: Positive Skew...
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This note was uploaded on 12/14/2009 for the course ECE 6130 taught by Professor Staff during the Fall '08 term at Georgia Tech.

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clocking - ECE 6130/4130 Advance VLSI Systems Fall 2009...

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