Design of an FPGA Logic Element for Implementing Asynchronous NULL Convention Logic Circuits

Two versions of a reconfigurable logic element are developed for use in constructing afield-programmable gate array NULL convention logic (NCL) field-programmable gate array (FPGA): one with extra embedded registration capability, which requires additional area, and one without. Both versions can be configured as any of the 27 fundamental NCL gates, including resettable and inverting variations, and both can utilize embedded registration for gates with three or fewer inputs; however, only the version with the additional embedded registration capability can utilize embedded registration with four-input gates. These two approaches are compared with each other and with an existing approach, showing that both versions developed herein yield a more area efficient NCL circuit implementation, compared to the previous work. The two FPGA logic elements are simulated at the transistor level using the 1.8-V, 180-nm TSMC CMOS process.     

Design for Test of Asynchronous NULL Convention Logic (NCL) Circuits

Due to the absence of a global clock and the presence of more state holding elements that synchronize the control and data paths, conventional Automatic Test Pattern Generation (ATPG) algorithms fail when applied to asynchronous circuits, leading to poor fault coverage. This paper presents a design for test (DFT) technique for a popular asynchronous design paradigm called NULL Convention Logic (NCL) aimed at making NCL designs testable using existing DFT tools with reasonable gate overhead. The proposed technique performs test points (TPs) insertion using Sandia Controllability and Observability Program (SCOAP) analysis to enhance the controllability of feedback nets and observability for fault sites that are flagged unobservable. An Automatic DFT Insertion Flow (ADIF) algorithm and a custom ATPG NCL primitive gates library are developed. The developed DFT technique has been verified on several NCL benchmark circuits

异步零协议算术逻辑单元的设计

异步电路在低功耗、低噪声、抗干扰、无时钟偏移、高鲁棒性和模块化设计等方面有较高的性能.设计了一个异步4位8操作码的算术逻辑单元,使用了双轨延时不敏感零协议逻辑结构,同时比较了使用流水线结构和非流水线结构以及相关的面积和速度优势.结果显示平均速度最快的结构比非流水线结构快了1.73倍,而面积需要增加了133%.     

Power Reduction of Asynchronous Logic Circuits Using Activity Detection

Asynchronous circuits are well known for their benefits in terms of dynamic power savings because asynchronous logic does not switch when inactive. Nevertheless, in deep-submicron technologies, leakage currents have become an increasing issue, and thus, asynchronous circuits need to focus on static-power-consumption reduction. In this paper, we propose an innovative way to detect incoming asynchronous activity. Associated to an automatic power regulation, it efficiently reduces the supply voltage and, thus, both energy per operation and leakage currents. The proposed technique has been applied to an asynchronous network-on-chip node and successfully implemented in an ST Microelectronics CMOS 65-nm technology.      

异步组合电路网表优化的研究

根据异步组合电路的特点，本章在传统的工艺映射算法的分解和覆盖两个步骤之间引进了新的一步-“延时再优化”，采用NAND3-Rotation的方法实现，对分解后网表的平均延时进行优化.在标准测试电路上的测试结果表明引进延时再优化能给异步电路的平均延时带来6～25%的改进。     

Layout-based Single Event Mitigation Techniques for Dynamic Logic Circuits

Due to the intrinsic lack of restoring paths, dynamic logic circuits have significant single-event susceptibility, and thus, they are not preferred in applications requiring high reliability when compared to static logic. However, in high speed applications, this circuit family is still very attractive. This papers presents two layout-based single-event resilient dynamic logic designs. The resultant SET pulse is suppressed because of charge-sharing in the layout-level. Simulation results verify that they enjoy higher single event tolerance. Experimental results validate the fact that approximately 20?~?30 % of magnitude reduction in cross-section is achieved in both designs. On the other hand, the increase in single-event performance is achieved at the expense of power and area overheads of 10 and 15 %, respectively, using our layout style in 130 nm CMOS bulk technology.     

无线局域网通信芯片可测性设计及实现

可测性设计已应用在大规模集成电路设计中。本文介绍了可测性设计原理和实现技术。同时介绍了一款无线局域网(WLAN)芯片,根据该芯片的结构特点,介绍了本款芯片应用的可测性技术以及实现过程,对使用的EDA工具及设计方法进行了深入描述。最后对可测性设计实现的效果进行了说明,并给出部分测试结果。     

Synchronous Full-Scan for Asynchronous Handshake Circuits

Handshake circuits form a special class of asynchronous circuits that has enabled the industrial exploitation of the asynchronous potential such as low power, low electromagnetic emission, and increased cryptographic security. In this paper we present a test solution for handshake circuits that brings synchronous test-quality to asynchronous circuits. We add a synchronous mode of operation to handshake circuits that allows full controllability and observability during test. This technique is demonstrated on some industrial examples and gives over 99% stuck-at fault coverage, using test-pattern generators developed for synchronous circuits. The paper describes how such a full-scan mode can be achieved, including an approach to minimize the number of dummy latches in case latches are used in the data path of the handshake circuit.     

Functional Fault Equivalence and Diagnostic Test Generation in Combinational Logic Circuits Using Conventional ATPG

Fault equivalence is an essential concept in digital design with significance in fault diagnosis, diagnostic test generation, testability analysis and logic synthesis. In this paper, an efficient algorithm to check whether two faults are equivalent is presented. If they are not equivalent, the algorithm returns a test vector that distinguishes them. The proposed approach is complete since for every pair of faults it either proves equivalence or it returns a distinguishing vector. The advantage of the approach lies in its practicality since it uses conventional ATPG and it automatically benefits from advances in the field. Experiments on ISCAS’85 and full-scan ISCAS’89 circuits demonstrate the competitiveness of the method and measure the performance of simulation for fault equivalence.     

组合逻辑多故障诊断

通过对布尔差分法的剖析,得到了组合电路单固定故障测试生成的简化方法。该方法不必进行异或运算,只须求解恒等式就能得到组合逻辑电路的８测试矢量。多故障的测试码产生可以对高阶布差分经过变换,转化为一阶布尔差分来处理,从而极大地减少了多故障测试生成的计算工作量。     

逻辑电路神经网络模型

本文采用Hopfiold神经网络模型,从基本逻辑器件的真值表出发,建立其能量约束方程组,利用线性方程组理论推导出逻辑器件神经网络模型存在的充分必要条件,并由此得到基本逻辑门神经网络参数的一般表达式.     

Asynchronous Techniques for System-on-Chip Design

SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed.     

异步电路的设计方法及其应用

由于异步电路不仅具有高性能、低功耗、模块性等优势,而且有望解决微系统芯片中存在的模块互联难题,并被越来越多地应用于芯片的设计中,因而近年来引起了人们的高度重视.文章对研究较多的Huffman电路、延时无关电路、速度无关电路以及定时电路等的设计风格及其工具进行了对比分析,并提出了异步电路的发展趋势及其应用领域.     

脉冲异步时序电路分析与设计中应注意的两个问题

讨论了脉冲异步时序电路分析与设计中的一些问题,指出了状态信号反馈对触发器时钟信号的影响和传输延迟状态转换的影响。     

Subthreshold Source-Coupled Logic Circuits for Ultra-Low-Power Applications

This paper presents a novel approach for implementing ultra-low-power digital components and systems using source-coupled logic (SCL) circuit topology, operating in weak inversion (subthreshold) regime. Minimum size pMOS transistors with shorted drain-substrate contacts are used as gate-controlled, very high resistivity load devices. Based on the proposed approach, the power consumption and the operation frequency of logic circuits can be scaled down linearly by changing the tail bias current of SCL gates over a very wide range spanning several orders of magnitude, which is not achievable in subthreshold CMOS circuits. Measurements in conventional 0.18 m CMOS technology show that the tail bias current of each gate can be set as low as 10 pA, with a supply voltage of 300 mV, resulting in a power-delay product of less than 1 fJ. Fundamental circuits such as ring oscillators and frequency dividers, as well as more complex digital blocks such as parallel multipliers designed by using the STSCL topology have been experimentally characterized.     

厚膜混合集成电路可靠性技术

总结了混合集成电路的主要失效模式,在此基础上,主要从混合集成电路的设计和工艺两方面分析了其产生的原因,通过设计、工艺、原材料和元器件等方面采取对策和措施,达到提高混合集成电路可靠性的目的.     

Soft-Error Tolerance and Mitigation in Asynchronous Burst-Mode Circuits

We discuss the problem of soft errors in asynchronous burst-mode machines (ABMMs), and we propose two solutions. The first solution is an error tolerance approach, which leverages the inherent functionality of Muller C-elements, along with a variant of duplication, to suppress all transient errors. The proposed method is more robust and less expensive than the typical triple modular redundancy error tolerance method and often even less expensive than previously proposed concurrent error detection methods, which only provide detection but no correction. The second solution is an error mitigation approach, which leverages a newly devised soft-error susceptibility assessment method for ABMMs, along with partial duplication, to suppress a carefully chosen subset of transient errors. Three progressively more powerful options for partial duplication select among individual gates, complete state/output logic cones, or partial state/output logic cones and enable efficient exploration of the tradeoff between the achieved soft-error susceptibility reduction and the incurred area overhead. Furthermore, a gate-decomposition method is developed to leverage the additional soft-error susceptibility reduction opportunities arising during conversion of a two-level ABMM implementation into a multilevel one. Extensive experimental results on benchmark ABMMs assess the effectiveness of the proposed methods in reducing soft-error susceptibility, and their impact on area, performance, and offline testability.      

Cellular Array-based Delay-insensitive Asynchronous Circuits Design and Test for Nanocomputing Systems

This paper presents the design, layout, and testability analysis of delay-insensitive circuits on cellular arrays for nanocomputing system design. In delay-insensitive circuits the delay on a signal path does not affect the correctness of circuit behavior. The combination of delay-insensitive circuit style and cellular arrays is a useful step to implement nanocomputing systems. In the approach proposed in this paper the circuit expressions corresponding to a design are first converted into Reed–Muller forms and then implemented using delay-insensitive Reed–Muller cells. The design and layout of the Reed–Muller cell using primitives has been described in detail. The effects of stuck-at faults in both delay-insensitive primitives and gates have been analyzed. Since circuits implemented in Reed–Muller forms constructed by the Reed–Muller cells can be easily tested offline, the proposed approach for delay-insensitive circuit design improves a circuit’s testability. Potential physical implementation of cellular arrays and its area overhead are also discussed.