串行数据检测器的设计

分析了时序逻辑电路设计中的状态化简问题,指出了状态化简不会改变电路的逻辑功能,不可能使电路产生错误输出。讨论了串行数据检测器的米里型电路设计和摩尔型电路设计,提出了一种在输入数据稳定的区段进行检测、确定电路状态,在输入数据改换为下一位时输出状态信息,确保系统正常工作的米里型电路设计方法,这种方法对米里型电路的设计有通用性。     

手把手教你学CPLD／FPGA设计（十一）上

组合逻辑电路的设计实验 数字逻辑电路系统按功能的不同,可以分为组合逻辑电路和时序逻辑电路两大类。组合逻辑电路在任意时刻产生的输出只取决于该时刻的输入,而与电路过去的输入无关。常见的组合逻辑电路有数据选择器、编码器、译码器、加法器等。     

利用条件输出增多EPROM的数据线

利用条件输出增多EPROM的数据线的基本方法和原理，介绍了用组合逻辑电路和时序逻辑电路实现条件输出的实例。     

基于数据选择器和D触发器的多输入时序电路设计

为了探索多输入时序逻辑电路的简便实现方法,介绍了基于数据选择器和D触发器的多输入时序逻辑电路设计技术。即将D触发器和数据选择器进行组合,用触发器的现态作为数据选择器选择输入变量、数据选择器的输出函数作为触发器的D输入信号,构成既有存储功能又有数据选择功能的多输入端时序网络。由触发器的现态选择输入变量、所选择的输入变量决定触发器的次态转换方向。该方法适合实现互斥多变量时序逻辑电路,且在设计过程中不需要进行函数化简。     

同步时序逻辑电路设计步骤研究

通过对时序逻辑电路设计部分教学过程的设计步骤分析研究,强化了原始状态的确定在设计过程中的重要性,在清晰设计思路,强化时序逻辑电路经典的设计方法的同时,补充了与实践应用相关的设计实例,完善了时序逻辑电路的设计步骤。     

Verilog-HDL讲座 第八讲 用Verilog-HDL做CPLD设计——时序逻辑电路的实现

在第七讲中,已经介绍了组合逻辑电路的实现。组合逻辑电路的特点是:在任意时刻,电路产生的稳定输出仅与当前时刻的输入有关。时序逻辑电路则与它不同,其特点是:在任意时刻电路产生的稳定输出不仅与当前时刻的输入有关,而且还与电路过去的输入有关。本讲中将介绍时序逻辑电路的实现。8.1 闪烁灯的实现在目标板上,设计有一个10MHz的时钟源。假如直接把它输出到发光二级管LED,由于人眼的延迟性,我们将无法看到LED闪烁,认为它一直亮着。如果我们期望看到闪烁灯,就需要将时钟源的频率降低后再输出。因此,可以采用如图1所示的逻辑功能框图。其…     

基于JK驱动方程的改进方法的电路自启动设计

时序逻辑电路的设计过程中,如何用JK触发器设计电路,设计好的电路是否能够自启动是必须考虑的问题,也是数字电子技术课程教学的重点和难点内容。文章结合实例,详细介绍了选用JK触发器设计同步时序逻辑电路时,利用次态卡诺图改进方法直接得出各触发器的最简驱动方程。验证电路是否能够自启动,如果不能自启动通过修改次态卡诺图的方法,实现用JK触发器设计能自启动的同步时序逻辑电路。     

运用MSI设计时序逻辑电路(二)——设计异步脉冲序列检测器

本文是《运用MSI设计时序逻辑电路(一)——设计同步脉冲序列检测器》一文的妹篇.除对二者之间共性的问题进行简要的阐述之外,重点放在解决异步时序逻辑电路的特殊问题.即时钟脉冲CP的安排问题上.至于这两篇文章的共同思想,都是运用中规模集成电路(MSI)为基本单元,探寻运用MSI设计时序逻辑电路的方法.运用MSI设计异步脉冲序列检测器.关键问题有两上:一是电路的基本结构;二是时钟脉冲CP的安排.对于前者,根据对脉冲异步序列检测器输入、输出逻辑关系的分析.我们发现其基本规律与脉冲同步序列相似,因此,本文仍采用与前文相同的基本结构,即选用具有“串入一并出”功能的芯片(如移位寄存器)和具有“识别并行代码”功能的芯片(如数字比较器.串行进位加法器、多路选择器、译码器等)来组成基本电路.所以,剩下的问题就是如何安排时钟脉冲CP.下面通过两个具体例子来阐明设计方法.     

时序逻辑电路故障的一种检测方法

阐述了时序逻辑电路的故障检测序列集的生成和验证方法,说明了主要包括,状态描述,检测序列生成,模拟验证,其中检测序列集的生成和检测最为重要,只要得一经过检验的检测序列集,那么顺序地向待测电路施加检测序列,并逐次测量电路的响应,就可以达到电路故障检测的目的。     

通用的全帧型面阵CCD时序发生器设计方法

介绍了面阵CCD485的内部结构、工作模式,并给出了其基本驱动电路设计。然后通过对面CCD485驱动时序图的分析,分析了全帧型大面阵CCD 的正常工作、快速擦除、图像窗口输出和像元合并的驱动时序,提出了一种基于时序细分和有限状态机的通用型全帧型面阵CCD驱动时序发生器设计方法。该方法通过对CCD 驱动时序进行分组,将每一组时序的波形划分为若干个基本输出状态,这样CCD 各个工作阶段所需的驱动时序都可以由各基本状态组合出来,使用摩尔型有限状态机来描述,将时序驱动器进行了模块化设计。给出了各个模块的具体设计,使时序发生器的设计过程更加简单,最后采用Xilinx公司的Virtex-ⅡPro系列FPGA-XC2VP20、ISE软件平台,设计了CCD驱动时序发生器,并进行了波形仿真分析。输出信号完全满足485芯片的驱动时序要求,证明了该设计方法的有效性。     

基于概率转移矩阵的时序电路可靠度估计方法

传统的概率转移矩阵(Probabilistic Transfer Matrix,PTM)方法是一种能够比较精确地估计软差错对门级电路可靠度影响的方法,但现有的方法只适用于组合逻辑电路的可靠度估计.本文提出基于PTM的时序电路可靠度估计方法(reliability estimation of Sequential circuits based on PTM,S-PTM),先把待评估时序电路划分为输出逻辑模块和次态逻辑模块,然后用本文提出的时序电路PIM计算模型得到电路的PIM,最后根据输入信号的概率分布计算出时序电路的可靠度.用ISCAS 89基准电路为对象进行实验和验证,实验表明所提方法是准确和合理的.     

Initialization of Sequential Circuits and its Application to ATPG

A general method for determining whether a certain design is initializable, and for generating its initialization sequence, is presented in this paper. This method is based on structural decomposition of the circuit, and can handle both logical (using X-value simulation) and functional initializability. The routines developed are then used for ATPG of sequential circuits. A pre-test sequence that initializes the good and as many of the faulty machines as possible is generated and used in conjunction with CRIS [5], a simulation based sequential ATPG program, to generate a test set for the circuit.     

基于连续逻辑的十值十进制算术运算电路的设计

本文提出了用ＤＹＬ系列器件构成的直接用十进制进行运算的十值电路。ＤＹＬ器件是一种线性元件,它可以工作于０－３Ｖ范围内的任意信号电压,对信号的分辨率极高,为实现高信息密度的十值电路提供了方便条件。本文提出的电路其工作原理是基于一种我们称之为“赋值－选通”的方法,将可能的输出值全部赋予电路,根据输入信息,通过选通电路直接将计算结果输出,这种赋值－选通法对多值电路的设计有普遍意义。     

Parallel sequence fault simulation for synchronous sequential circuits

A novel parallel sequence fault simulation (PSF) algorithm for synchronous sequential circuits is presented. The algorithm successfully extend the parallel pattern method for combinational circuits to sequential circuits by proposing a multiple-pass mechanism to overcome the state dependency in sequential circuits. The fault simulation is performed in parallel by partitioning the entire sequence into subsequences of equal length. Furthermore, techniques are developed to minimize the number of simulation passes. Notably, two compact counters, C _x and C _d , are proposed to faciliate the early stabilization detection of faulty circuit simulation with minimum space overhead. The experimental results on the benchmark circuits show that the speedup ratio over a serial sequence fault simulator based on ROOFS is 9.16 on average for pseudo random vectors. The parallel sequence algorithm of PSF is especially adaptable to parallel and distributed simulation which exploits sequence partition.     

Output-extended sequential machines

A new class of sequential machine, called output-extended, is defined. In contradistinction to Moore and Mealy machines, the output state here is a function of the previous output as well as the present state and input. A particular form of output-extended machine is studied, in which the function in question is the Boolean intersection of the present output in the Mealy sense and the previous output. It is shown that this structure offers possibilities of state reduction not present in the orginal Mealy machine.     

三值电压型CMOS施密特电路研究

首先对二值ＣＭＯＳ施密特电路的设计思想进行了分析,指出设计施密特电路的关键为阈值控制电路。根据三值ＣＭＯＳ电路有两个信号检测阈的特点,提出了通过文字电路将两个检测阈分离后进行分别控制并由文字电路的输出去控制ＣＭＯＳ传输门的设计方法,由此设计了三值ＣＭＯＳ施密特反相器。ＰＳＰＩＣＥ模拟证明了所设计的电路具有理想的施密特电路功能     

Monitoring machine based synthesis technique for concurrent error detection in finite state machines

This paper discusses a new design methodology for concurrent error detection in synchronous sequential circuits based on the use of monitoring machines. In this approach, an auxiliary sequential circuit, called the monitoring machine, operates in lock-step with the main machine, such that any fault in either of the two machines is immediately detected. This methodology is independent of the fault model. It can be applied to FSMs with pre-encoded states and can also be used for ones being synthesised. It also provides a systematic framework for the combined optimisation of the main and monitoring machines, and for exploring tradeoffs in their implementation. The design of monitored sequential circuits is a two-fold problem; namely one of designing an optimal monitoring machine given the main machine, and the other of encoding the main machine states so that the resulting monitoring machine is minimal. This paper formally discusses the design of both the main and monitoring machines and techniques for their combined optimisation. Tradeoffs in their implementation based on selective fault detection are also examined. Through experimental results, it is shown that the proposed synthesis technique is eminently suitable for the design of low-cost sequential circuits with concurrent error detection. The monitoring machine is less costly than the main machine. It is also not identical to it. As a result, a monitored sequential circuit has significantly lower hardware cost and improved fault coverage than previous implementations. Presently at Texas Instruments (India) Ltd., Bangalore, India.     

Precomputation-based sequential logic optimization for low power

We address the problem of optimizing logic-level sequential circuits for low power. We present a powerful sequential logic optimization method that is based on selectively precomputing the output logic values of the circuit one clock cycle before they are required, and using the precomputed values to reduce internal switching activity in the succeeding clock cycle. We present two different precomputation architectures which exploit this observation. The primary optimization step is the synthesis of the precomputation logic, which computes the output values for a subset of input conditions. If the output values can be precomputed, the original logic circuit can be “turned off” in the next clock cycle and will have substantially reduced switching activity. The size of the precomputation logic determines the power dissipation reduction, area increase and delay increase relative to the original circuit. Given a logic-level sequential circuit, we present an automatic method of synthesizing precomputation logic so as to achieve maximal reductions in power dissipation. We present experimental results on various sequential circuits. Up to 75% reductions in average switching activity and power dissipation are possible with marginal increases in circuit area and delay     

基于二叉树的时序电路测试序列设计

为了实现时序电路状态验证和故障检测,需要事先设计一个输入测试序列。基于二叉树节点和树枝的特性,建立时序电路状态二叉树,按照电路二叉树节点(状态)与树枝(输入)的层次逻辑关系,可以直观和便捷地设计出时序电路测试序列。用测试序列激励待测电路,可以验证电路是否具有全部预定状态,是否能够实现预定状态转换。