时钟偏移调度的定时优化

Timing

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"Timing Optimization Through Clock Skew Scheduling" by Ivan S. Kourtev, Baris Taskin, and Eby G. Friedman 本书深入探讨了时序优化中的关键问题，特别是通过时钟偏移调度来提升集成电路性能的技术。时钟偏移调度允许不同部分的电路在不同的时间开始工作，从而减少整体的时序延迟。以下是对标题和描述中提到的知识点的详细解释： 1. **非零时钟偏移调度**：基于Friedman和Fishburn的开创性工作，书中提出了一种方法，将这种方法与线性规划（LP）技术结合，用于电路设计和时钟分配网络的拓扑结构设计。这种方法尤其适用于具有级敏锁存器和多相时钟信号的电路。 2. **混合整数线性规划问题**：同时考虑时钟调度和时钟树拓扑综合的问题被形式化为一个混合整数线性规划问题，可以高效求解。这种方法在多种基准电路和工业电路上的应用显示，同步性能提高了60%以上。 3. **可靠性优先的优化方案**：对于那些要求高可靠性和生产良率的场景，书中提出了基于二次规划（QP）的成本函数问题。这允许在考虑参数变化的约束下，解决时钟调度的容忍度问题。使用拉格朗日乘子法迭代解决约束版本的问题，特别适合输入/输出（I/O）接口和知识产权（IP）块的设计，其中时钟延迟和偏移要求被充分整合到数学模型中。 4. **理论限制分析**：书中讨论了通过时钟偏移调度所能实现的时钟周期改进的理论极限。通过对三种局部数据路径拓扑进行分析，确定了这些限制。针对重聚路径系统，提出了一种缓解时钟偏移调度限制的方法，通过在部分数据路径上插入延迟，该方法也形式化为一个LP问题，以便自动化应用。 5. **新兴时钟生成与分布技术**：针对旋转谐振时钟技术，书中介绍了时钟偏移调度的实用性和必要性。展示了初步的建模和实施成果，并详细阐述了如何将时钟偏移调度整合到完整的物理设计流程中，以自动化设计旋转时钟同步电路。这本书为电子设计自动化领域的工程师和研究人员提供了关于时序优化和时钟偏移调度的深入理解和实用工具，有助于提升集成电路的性能和效率，特别是在处理复杂电路和新兴技术时。

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Introduction

The concept of data or information processing arises in a variety of ﬁelds.

Understanding the principles behind this concept is fundamental to computer

design, communications, manufacturing process control, biomedical engineer-

ing, and an increasingly large number of other areas in technology and science.

It is impossible to imagine modern life without computers for generating, ana-

lyzing and retrieving large amounts of information, as well as communicating

information regardless of location.

Technologies for designing and building microelectronics-based computa-

tional equipment have been steadily advancing ever since the ﬁrst commercial

discrete integrated circuits (ICs) were introduced in the late 1950’s [3].

predicted by Moore’s Law in the 1960’s [4], integrated circuit density has been

doubling approximately every 18 months. This scaling of circuit size has been

accompanied by a similar exponential increase in circuit speed (or more pre-

cisely, clock frequency). These trends of steadily increasing circuit size and

clock frequency are illustrated in Figures 1.1 and 1.2, respectively. As a result

of this amazing revolution in semiconductor technology, it is not unusual for

modern integrated circuits to contain over ten million switching elements (i.e.,

transistors) packed into a chip area as large as 500 mm

(e.g., [5, 6, 7]). This

truly exceptional technological capability is due to advances in both design

methodologies and physical manufacturing technologies. Research and experi-

ence demonstrate that this trend of exponentially increasing integrated circuit

computational power will continue into the foreseeable future.

Integrated circuit performance is typically characterized [8] by the speed

of operation, the available circuit functionality, and the power consumption,

and there are multiple factors which directly aﬀect these performance charac-

teristics. While each of these factors is signiﬁcant, on the technological side,

Monolithic integrated circuits were ﬁrst introduced in the early 1960’s.

I.S. Kourtev et al., Timing Optimization Through Clock Skew Scheduling, 1

DOI: 10.1007/978-0-387-71056-3

 Springer Science+Business Media LLC 2009

4 1 Introduction

of fully synchronous VLSI systems, these eﬀects have the potential to create

catastrophic failures due to the limited time available for signal propagation

among the gates.

The material presented in this monograph is associated with these afore-

mentioned delay eﬀects from the perspective of a synchronous digital VLSI

system. The research results described here can be used to improve the per-

formance and reliability of a synchronous VLSI circuit through the design of

the clock distribution network common to any synchronous digital system.

Speciﬁcally, new algorithms for scheduling the arrival time of the clock sig-

nals at the individual registers (or synchronous macro blocks) of a circuit

and synthesizing the overall clock tree are discussed. Operational character-

istics, performance improvements and limitations to suggested improvements

are presented in a cohesive manner.

To provide an intuitive perspective into the topics discussed here, consider

the simple synchronous circuit shown in Figure 1.3 [9]. Two consecutively con-

nected local data paths, consisting of the registers, R

and R

,andR

and R

respectively, are depicted in this ﬁgure. Consider that, by design, clock delays

to R

and R

must be identical. That is, the clock signal C

to the register

is synchronized

with the clock signal C

to R

. The signal delays through

the registers are considered identical in this example, numerically assigned

to 2 ns. Under this identical register delay assumption, the path from R

is the worst case path (since it has a larger logic signal delay). By delaying

the clock signal C

to the register R

with respect to the clock signal to the

,aleading (or negative) clock skew is added to this local data path

from R

to R

. As the clock delays to R

and R

are designed to be identical, a

certain amount of lagging (or positive) clock skew is applied to the local data

path from R

to R

. Thus, the clock signal C

should be designed to lead the

clock signal C

by 1.5 ns, thereby forcing both paths R

to R

and R

to R

to have the same total eﬀective local data path delay (consisting of propaga-

Data

Clock

Data

Clock

Data

Clock

Logic Logic

Clock Signal

Data Signal

Delay =4ns Delay =7ns

=3ns T

=1.5 ns T

=3ns

Fig. 1.3. Example of applying localized negative clock skew to a synchronous circuit.

The signals C

and C

arrive at the same time with no delay or advance with

respect to each other.

1 Introduction 5

tion delay T

and local data path skew T

Skew

) T

+ T

Skew

=7.5ns. The

delay of the critical path (R

to R

) of the synchronous circuit is temporally

reﬁned to the precision of the clock distribution network, and the entire sys-

tem (for this simple example) could operate at a maximum clock frequency of

133.3 MHz. Note that, if no localized clock skew were applied, the maximum

possible frequency would be 111.1 MHz. The performance characteristics of

the system, both with and without the application of localized clock skew, are

summarized in Table 1.1.

Table 1.1. Performance characteristics of the circuit shown in Figure 1.3 without

and with localized clock skew.

Local Data Path

(

min

)

with

Skew

(

min

)

with

zero skew non-zero skew

;

4+2+0=6 3 1.5 1.5 4+2+1

5=7

;

7+2+0=9 1.5 3 -1.5 7+2− 1

5=7

max

111

1MHz 133

3MHz

Note that |T

Skew

| <T

(since |−1.5ns| < 9 ns) for the local data

path from R

to R

. Therefore, it is ensured that the correct data signal is

successfully latched into R

and no local data path/clock skew constraint rela-

tionship is violated. This design technique of applying localized clock skew is

particularly eﬀective in sequentially-adjacent, temporally irregular local data

paths; however, it is applicable to any type of synchronous sequential sys-

tem. For certain architectures, a signiﬁcant improvement in performance and

reliability is both possible and likely.

One of the objectives of this research monograph is to provide detailed

insight into the systematic application of the technique exempliﬁed in Fig-

ure 1.3 and Table 1.1 and described above to synchronous sequential digital

circuits of arbitrary structure and size. To this end, the basic properties of

CMOS-based digital integrated circuits as well as the fundamental principles

of synchronous VLSI system operation are reviewed in Chapter 2.

In Chapters 3 and 4, the timing issues related to the implementation of

synchronous VLSI circuits are discussed. A summary of the deﬁnitions and

notations used in this monograph is presented. Signal delay in CMOS digital

integrated circuits is presented in Chapter 3 where the sources of both device

and interconnect delays are discussed.

In Chapter 4, the fundamental timing relationships of synchronous digital

systems are summarized as these relationships are key to understanding the

algorithms presented in Chapters 5 and 7. More speciﬁcally, Chapter 4 de-

scribes in considerable detail the properties of both the various types of timed

storage elements and of the data paths built with these elements.

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时钟偏移调度的定时优化

Timing Constraints and Clock Tree Synthesis

Synopsys_Timing_Constraints_and_Optimization_User_Guide.pdf

Vivado中如何进行时序优化（Timing Optimization）

clock tree和clock skew group

什么是clock skew

A non-unate path in clock network for clock

synopsys timing constraints and optimization user guide

数字设计的innovus的命令中： set timing_disable_clock_gating_checks false是做什么用的

STA Basic Tutorial

void Timing_Handle() //定时处理 100MS调用 { static u8 Last_Timing = 0; static u16 Timing_Cnt = 0; if(Last_Timing != Timing) { Last_Timing = Timing; Timing_Cnt = 0; } if(Timing == 0) { return; } if(++Timing_Cnt >= 36000) { if(--Timing == 0) { Power = 0; } } }优化这段代码

还有别的FPGA面试题目吗

综合后的transition time不满足要求

System Clock Configuration

vivado timing report

function void judge_timing_range(input real timing_range); real range; if(timing_range<1000) return range=timing_range*25; endfunction

function judge_timing_range(input real timing_range); real range; if(timing_range<1000) return range=timing_range*25; endfunction

skew transition

Django 安装包 linux

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