lecture19 - ECE520 VLSI Design Lecture 19: Clock...

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1 ECE520 – Lecture 19 Slide: 1 University of New Mexico Office: ECE Bldg. 230B Office hours: Tuesday 2:00-3:00PM or by appointment E-mail: payman@ece.unm.edu Payman Zarkesh-Ha ECE520 – VLSI Design Lecture 19: Clock Distributions - PLL ECE520 – Lecture 19 Slide: 2 University of New Mexico Review of Last Lecture Timing Issues Critical Path False Path Clock Skew Clock Jitter
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2 ECE520 – Lecture 19 Slide: 3 University of New Mexico Today’s Lecture Clock Distribution Network Clock generation (PLLs) Clock distribution Clock gaters ECE520 – Lecture 19 Slide: 4 University of New Mexico Physical Clock Distributing a single clock across a chip is challenging Distributing more than one clock signal is almost impossible Most systems distribute a single GLOBAL CLOCK even if the system needs multiple logical clocks Local clock gaters located close to the clocked elements produce the actual physical clocks and drive the clock to the elements along short wires Clock gaters are: Buffers AND gates for clock gating Inverters to produce complementary clocks Pulse generators for pulsed latches
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3 ECE520 – Lecture 19 Slide: 5 University of New Mexico Clock System Architecture IC receives an external clock signal through the I/O pads The clock generation unit adjusts the phase and/or frequency of the global clock by either Phase-locked loop (PLL) or Delay-locked loop (DLL) The generated global clock is then distributed to points near all of the clocked elements via a clock distribution network Local gaters receive this global clock and drive the physical clock signals along short wires to small groups of clocked elements ECE520 – Lecture 19 Slide: 6 University of New Mexico Global Clock Generation Global clock generator receives an external clock signal and produces the global clock that is distributed across the die
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This note was uploaded on 01/11/2011 for the course ECE 520 taught by Professor Zarkesh-ha,p during the Fall '08 term at New Mexico.

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lecture19 - ECE520 VLSI Design Lecture 19: Clock...

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