Topic

# Clock skew

About: Clock skew is a research topic. Over the lifetime, 17395 publications have been published within this topic receiving 219473 citations. The topic is also known as: timing skew & clock timing skew.

##### Papers published on a yearly basis

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03 Nov 2004TL;DR: The FTSP achieves its robustness by utilizing periodic flooding of synchronization messages, and implicit dynamic topology update and comprehensive error compensation including clock skew estimation, which is markedly better than that of the existing RBS and TPSN algorithms.

Abstract: Wireless sensor network applications, similarly to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. This paper describes the Flooding Time Synchronization Protocol (FTSP), especially tailored for applications requiring stringent precision on resource limited wireless platforms. The proposed time synchronization protocol uses low communication bandwidth and it is robust against node and link failures. The FTSP achieves its robustness by utilizing periodic flooding of synchronization messages, and implicit dynamic topology update. The unique high precision performance is reached by utilizing MAC-layer time-stamping and comprehensive error compensation including clock skew estimation. The sources of delays and uncertainties in message transmission are analyzed in detail and techniques are presented to mitigate their effects. The FTSP was implemented on the Berkeley Mica2 platform and evaluated in a 60-node, multi-hop setup. The average per-hop synchronization error was in the one microsecond range, which is markedly better than that of the existing RBS and TPSN algorithms.

2,267 citations

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TL;DR: This paper describes a circuit transformation called retiming in which registers are added at some points in a circuit and removed from others in such a way that the functional behavior of the circuit as a whole is preserved.

Abstract: This paper describes a circuit transformation calledretiming in which registers are added at some points in a circuit and removed from others in such a way that the functional behavior of the circuit as a whole is preserved. We show that retiming can be used to transform a given synchronous circuit into a more efficient circuit under a variety of different cost criteria. We model a circuit as a graph in which the vertex setV is a collection of combinational logic elements and the edge setE is the set of interconnections, each of which may pass through zero or more registers. We give anO(?VźE?lg?V?) algorithm for determining an equivalent retimed circuit with the smallest possible clock period. We show that the problem of determining an equivalent retimed circuit with minimum state (total number of registers) is polynomial-time solvable. This result yields a polynomial-time optimal solution to the problem of pipelining combinational circuitry with minimum register cost. We also give a chacterization of optimal retiming based on an efficiently solvable mixed-integer linear-programming problem.

940 citations

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TL;DR: It is shown that clock frequencies in excess of 200 MHz are feasible in a 3- mu m CMOS process, and a precharge technique with a true single-phase clock, which increases the clock frequency and reduces the skew problems, is used.

Abstract: It is shown that clock frequencies in excess of 200 MHz are feasible in a 3- mu m CMOS process. This performance can be obtained by means of clocking strategy, device sizing, and logic style selection. A precharge technique with a true single-phase clock, which increases the clock frequency and reduces the skew problems, is used. Device sizing with the help of an optimizing program improves circuit speed by a factor of 1.5-1.8. The logic depth is minimized to one instead of two or more, and pipeline structures are used wherever possible. Experimental results for several circuits which work at clock frequencies of 200-230 MHz are presented. SPICE simulation shows that some circuits could work up to 400-500 MHz. >

849 citations

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02 Feb 2002TL;DR: An alternative approach is described, which is called a multiple clock domain (MCD) processor, in which the chip is divided into several clock domains, within which independent voltage and frequency scaling can be performed.

Abstract: As clock frequency increases and feature size decreases, clock distribution and wire delays present a growing challenge to the designers of singly-clocked, globally synchronous systems. We describe an alternative approach, which we call a multiple clock domain (MCD) processor, in which the chip is divided into several clock domains, within which independent voltage and frequency scaling can be performed. Boundaries between domains are chosen to exploit existing queues, thereby minimizing inter-domain synchronization costs. We propose four clock domains, corresponding to the front end , integer units, floating point units, and load-store units. We evaluate this design using a simulation infrastructure based on SimpleScalar and Wattch. In an attempt to quantify potential energy savings independent of any particular on-line control strategy, we use off-line analysis of traces from a single-speed run of each of our benchmark applications to identify profitable reconfiguration points for a subsequent dynamic scaling run. Using applications from the MediaBench, Olden, and SPEC2000 benchmark suites, we obtain an average energy-delay product improvement of 20% with MCD compared to a modest 3% savings from voltage scaling a single clock and voltage system.

508 citations

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Bell Labs

^{1}TL;DR: Using a model to detect clocking hazards, two linear programs are investigated: minimizing the clock period, while avoiding clock hazards, and for a given period, maximizing the minimum safety margin against clock hazard.

Abstract: Improving the performance of a synchronous digital system by adjusting the path delays of the clock signal from the central clock source to individual flip-flops is investigated. Using a model to detect clocking hazards, two linear programs are investigated: (1) minimizing the clock period, while avoiding clock hazards, and (2) for a given period, maximizing the minimum safety margin against clock hazard. These programs are solved for a simple example, and circuit simulation is used to contrast the operation of a resulting circuit with the conventionally clocked version. The method is extended to account for clock skew caused by relative variations in the drive capabilities of N-channel versus P-channel transistors in CMOS. >

485 citations