都国清泽线术大然 1958 of Science and Technology 中国斜毡术大草 数字逻辑电路学习指导 学 院：信息科学技术学院 专 业：信息安全 姓 名：高源 指导教师：胡新伟老师
数字逻辑电路学习指导 学 院：信息科学技术学院 专 业：信息安全 姓 名：高源 指导教师：胡新伟老师
数字逻辑电路学习指导 2020秋数字逻辑电路06班 目录 1写给信息学院的学弟学妹们的一封信 6 2课程综述 7 2.1简介 7 2.2课程特点 7 2.3学习方法 8 3第一章数制和码制 10 3.1主要内容 10 3.2学习目标 10 3.3学习方法 10 3.4思考题… 11 3.5经典例题 12 4第二章逻辑代数基础 14 4.1主要内容 14 4.2学习目标 14 4.3学习方法 15 4.4思考题 15 4.5经典例题 17 5第三章门电路 21 5.1主要内容 21 5.2学习目标 21 5.3学习方法 22 5.4思考题 22 5.5经典例题 24 6第四章组合逻辑电路 26 6.1主要内容 26 6.2学习目标 26 6.3学习方法 26
数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 目录 1 写给信息学院的学弟学妹们的一封信 ························································ 6 2 课程综述 ···························································································· 7 2.1 简介 ························································································· 7 2.2 课程特点 ··················································································· 7 2.3 学习方法 ··················································································· 8 3 第一章 数制和码制 ············································································· 10 3.1 主要内容 ··················································································· 10 3.2 学习目标 ··················································································· 10 3.3 学习方法 ··················································································· 10 3.4 思考题 ······················································································ 11 3.5 经典例题 ··················································································· 12 4 第二章 逻辑代数基础 ·········································································· 14 4.1 主要内容 ··················································································· 14 4.2 学习目标 ··················································································· 14 4.3 学习方法 ··················································································· 15 4.4 思考题 ······················································································ 15 4.5 经典例题 ··················································································· 17 5 第三章 门电路 ··················································································· 21 5.1 主要内容 ··················································································· 21 5.2 学习目标 ··················································································· 21 5.3 学习方法 ··················································································· 22 5.4 思考题 ······················································································ 22 5.5 经典例题 ··················································································· 24 6 第四章 组合逻辑电路 ·········································································· 26 6.1 主要内容 ··················································································· 26 6.2 学习目标 ··················································································· 26 6.3 学习方法 ··················································································· 26 1
数字逻辑电路学习指导 2020秋数字逻辑电路06班 6.4思考题 27 6.5经典例题 29 7第五章半导体存储电路 30 7.1主要内容 30 7.2学习目标 30 7.3学习方法 31 7.4思考题 … 31 7.5经典例题 33 8第六章时序逻辑电路 34 8.1主要内容 34 8.2学习目标 34 8.3学习方法 35 8.4思考题 36 9第七章脉冲波形的产生和整形电路 40 9.1主要内容 40 9.2学习目标 40 9.3学习方法 41 9.4思考题 42 10第八章数一模和模—一数转换 45 10.1主要内容 45 10.2学习目标 45 10.3学习方法 46 10.4思考题 46 10.5经典例题 47 11第一章至第四章经典问题综合整理 50 11.1无关项的概念及其在化简逻辑函数中的应用 50 11.1.1无关项的概念 50 11.1.2约束项 50 11.1.3任意项 51 11.1.4无关项在化简中的应用 52 11.2逻辑函数不同表达形式之间的转换 53 11.2.1真值表转换为逻辑函数式 53 11.2.2逻辑函数式转换为真值表 53 11.2.3逻辑函数式转换为卡诺图… 53 2
数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 6.4 思考题 ······················································································ 27 6.5 经典例题 ··················································································· 29 7 第五章 半导体存储电路 ······································································· 30 7.1 主要内容 ··················································································· 30 7.2 学习目标 ··················································································· 30 7.3 学习方法 ··················································································· 31 7.4 思考题 ······················································································ 31 7.5 经典例题 ··················································································· 33 8 第六章 时序逻辑电路 ·········································································· 34 8.1 主要内容 ··················································································· 34 8.2 学习目标 ··················································································· 34 8.3 学习方法 ··················································································· 35 8.4 思考题 ······················································································ 36 9 第七章 脉冲波形的产生和整形电路 ························································ 40 9.1 主要内容 ··················································································· 40 9.2 学习目标 ··················································································· 40 9.3 学习方法 ··················································································· 41 9.4 思考题 ······················································································ 42 10 第八章 数——模和模——数转换 ························································· 45 10.1 主要内容 ·················································································· 45 10.2 学习目标 ·················································································· 45 10.3 学习方法 ·················································································· 46 10.4 思考题 ····················································································· 46 10.5 经典例题 ·················································································· 47 11 第一章至第四章经典问题综合整理 ························································· 50 11.1 无关项的概念及其在化简逻辑函数中的应用 ····································· 50 11.1.1 无关项的概念 ···································································· 50 11.1.2 约束项 ············································································· 50 11.1.3 任意项 ············································································· 51 11.1.4 无关项在化简中的应用 ························································ 52 11.2 逻辑函数不同表达形式之间的转换 ················································· 53 11.2.1 真值表转换为逻辑函数式 ····················································· 53 11.2.2 逻辑函数式转换为真值表 ····················································· 53 11.2.3 逻辑函数式转换为卡诺图 ····················································· 53 2
数字逻辑电路学习指导 2020秋数字逻辑电路06班 11.2.4波形图转换为真值表 54 11.3逻辑函数式常见形式变换 54 11.3.1与或式→与非与非式 54 11.3.2与或式→与或非式 54 11.3.3与或式→或与式… 55 11.3.4与或式→或非或非式 55 11.4怎样学习第三章 55 11.4.1基本电路一互补开关电路 55 11.4.2一种实现方法一二极管开关电路 56 11.4.3一种实现方法一MOS管基本开关电路 56 11.4.4一种实现方法一CM0S反相器 57 11.5关于高阻态 57 11.5.1概念 57 11.5.2表示方法 57 11.5.3注意事项 57 11.6可用来实现逻辑函数的常用组合逻辑电路模块 58 11.6.1译码器 58 11.6.2数据选择器 58 11.6.3加法器 58 11.7组合逻辑电路分析 58 11.7.1本质 58 11.7.2方法 59 11.7.3想法分析 59 11.8组合逻辑电路设计 59 11.8.1本质 59 11.8.2方法 59 11.8.3注意 60 11.9逻辑抽象问题 60 11.10译码器、数据选择器的应用及其比较 60 11.10.1译码器 60 11.10.2数据选择器 61 11.10.3应用 61 3
数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 11.2.4 波形图转换为真值表 ··························································· 54 11.3 逻辑函数式常见形式变换 ····························································· 54 11.3.1 与或式 ⇒ 与非与非式 ························································· 54 11.3.2 与或式 ⇒ 与或非式 ···························································· 54 11.3.3 与或式 ⇒ 或与式 ······························································· 55 11.3.4 与或式 ⇒ 或非或非式 ························································· 55 11.4 怎样学习第三章 ········································································· 55 11.4.1 基本电路——互补开关电路 ·················································· 55 11.4.2 一种实现方法——二极管开关电路 ········································· 56 11.4.3 一种实现方法——MOS 管基本开关电路 ································· 56 11.4.4 一种实现方法——CMOS 反相器 ··········································· 57 11.5 关于高阻态 ··············································································· 57 11.5.1 概念 ················································································ 57 11.5.2 表示方法 ·········································································· 57 11.5.3 注意事项 ·········································································· 57 11.6 可用来实现逻辑函数的常用组合逻辑电路模块 ·································· 58 11.6.1 译码器 ············································································· 58 11.6.2 数据选择器 ······································································· 58 11.6.3 加法器 ············································································· 58 11.7 组合逻辑电路分析 ······································································ 58 11.7.1 本质 ················································································ 58 11.7.2 方法 ················································································ 59 11.7.3 想法分析 ·········································································· 59 11.8 组合逻辑电路设计 ······································································ 59 11.8.1 本质 ················································································ 59 11.8.2 方法 ················································································ 59 11.8.3 注意 ················································································ 60 11.9 逻辑抽象问题 ············································································ 60 11.10 译码器、数据选择器的应用及其比较 ············································ 60 11.10.1 译码器 ··········································································· 60 11.10.2 数据选择器 ····································································· 61 11.10.3 应用 ·············································································· 61 3
数字逻辑电路学习指导 2020秋数字逻辑电路06班 11.11功能扩展专题 61 11.11.1本质 61 11.11.2“黑盒子”模型一解题方法 61 11.11.3以一道作业题目为例 63 11.12数制和码制例题补充 65 11.12.1十进制码和格雷码的转换 。。。。4。 65 11.12.2二进制码和BCD码的转换 65 11.13逻辑代数基础例题补充 66 11.13.1异或运算和同或运算 66 11.13.2利用公共项实现最简逻辑函数式 66 11.13.3无关项在化简中的应用 66 11.14加法器的应用 67 11.14.1加法器实现加减运算 。。。。。 67 11.14.2加法器实现乘法运算 67 11.15有限制的功能扩展问题 68 12第五章至第八章经典问题综合整理 70 12.1SR锁存器的约束条件与“不定”状态的理解 70 12.1.1简述… 70 121.2SR锁存器电路结构与特性表 70 12.1.3SR锁存器约束条件与“不定”状态的解读 71 12.2触发器的逻辑功能和触发方式 72 12.2.1简介 72 12.2.2逻辑功能和触发方式的关系 72 12.2.3关于逻辑功能 73 12.3触发器的异步置位问题 73 12.3.1简介… 73 12.3.2怎么识别是同步输入还是异步输入 73 12.3.3只有一个Sp或者RD 74 12.3.4异步输入对主从触发器如何影响 75 12.4触发器的动态特性 75 12.4.1简介 75 12.4.2考察要求和如何学习 76 4
数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 11.11 功能扩展专题 ·········································································· 61 11.11.1 本质 ·············································································· 61 11.11.2 “黑盒子”模型——解题方法 ············································· 61 11.11.3 以一道作业题目为例 ························································· 63 11.12 数制和码制例题补充 ································································· 65 11.12.1 十进制码和格雷码的转换 ··················································· 65 11.12.2 二进制码和 BCD 码的转换 ················································· 65 11.13 逻辑代数基础例题补充 ······························································ 66 11.13.1 异或运算和同或运算 ························································· 66 11.13.2 利用公共项实现最简逻辑函数式 ·········································· 66 11.13.3 无关项在化简中的应用 ······················································ 66 11.14 加法器的应用 ·········································································· 67 11.14.1 加法器实现加减运算 ························································· 67 11.14.2 加法器实现乘法运算 ························································· 67 11.15 有限制的功能扩展问题 ······························································ 68 12 第五章至第八章经典问题综合整理 ························································· 70 12.1 SR 锁存器的约束条件与“不定”状态的理解 ··································· 70 12.1.1 简述 ················································································ 70 12.1.2 SR 锁存器电路结构与特性表 ················································ 70 12.1.3 SR 锁存器约束条件与“不定”状态的解读 ······························ 71 12.2 触发器的逻辑功能和触发方式 ······················································· 72 12.2.1 简介 ················································································ 72 12.2.2 逻辑功能和触发方式的关系 ·················································· 72 12.2.3 关于逻辑功能 ···································································· 73 12.3 触发器的异步置位问题 ································································ 73 12.3.1 简介 ················································································ 73 12.3.2 怎么识别是同步输入还是异步输入 ········································ 73 12.3.3 只有一个 SD 或者 RD ························································· 74 12.3.4 异步输入对主从触发器如何影响 ··········································· 75 12.4 触发器的动态特性 ······································································ 75 12.4.1 简介 ················································································ 75 12.4.2 考察要求和如何学习 ··························································· 76 4
数字逻辑电路学习指导 2020秋数字逻辑电路06班 12.5时序逻辑电路分析 76 12.5.1简介 76 12.5.2分析方法 76 12.6常用时序逻辑电路模块 77 12.6.1简介 77 12.6.2同步置零、置位和异步置零、置位 77 12.6.3关于计数器进位输出信号 77 12.6.4以移位寄存器为例分析自启动问题 78 12.7同步时序逻辑电路设计 81 12.7.1简介… 81 12.7.2设计方法 81 12.7.3关于学习同步时序逻辑电路设计的一些小建议 83 12.8门电路、脉冲产生与整形电路、数模转换电路 84 12.8.1简介 84 12.8.2TTL电路和CMOS电路输入悬空问题 84 12.8.3性能参数 84 12.8.4学习上的建议 85 13期末模拟试卷 86 14致谢 94 5
数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 12.5 时序逻辑电路分析 ······································································ 76 12.5.1 简介 ················································································ 76 12.5.2 分析方法 ·········································································· 76 12.6 常用时序逻辑电路模块 ································································ 77 12.6.1 简介 ················································································ 77 12.6.2 同步置零、置位和异步置零、置位 ········································ 77 12.6.3 关于计数器进位输出信号 ····················································· 77 12.6.4 以移位寄存器为例分析自启动问题 ········································ 78 12.7 同步时序逻辑电路设计 ································································ 81 12.7.1 简介 ················································································ 81 12.7.2 设计方法 ·········································································· 81 12.7.3 关于学习同步时序逻辑电路设计的一些小建议 ························· 83 12.8 门电路、脉冲产生与整形电路、数模转换电路 ·································· 84 12.8.1 简介 ················································································ 84 12.8.2 TTL 电路和 CMOS 电路输入悬空问题 ··································· 84 12.8.3 性能参数 ·········································································· 84 12.8.4 学习上的建议 ···································································· 85 13 期末模拟试卷 ···················································································· 86 14 致谢 ································································································ 94 5
数字逻辑电路学习指导 2020秋数字逻辑电路06班 写给信息学院的学弟学妹们的一封信 亲爱的信息学院的学弟学妹们你们好： 我是高源，来自信息学院1702班，信息安全专业.2020年秋季学期在胡新伟老师 的数字逻辑电路班级(O6班)担任课程助教 在学习数字逻辑电路课程的时候，被这门课程中的迷人的电子学色彩所深深吸引 学习中注重把握课程特点，并基于课程特点展开深入思考以求得适合自己的学习方法， 这也许是我在学习这门课程的时候还算比较顺利的原因吧.也想把一些思考和心得和大 家分享，希望能够帮助有需要的同学解决一些学习这门课程中遇到的困难 有了2020年春季学期担任数理方程课程助教的经验后，这学期在开展工作时相对 更加顺利一些.考虑到有一些学习方法可以分享，以及针对大家在学习这门课程时常常 遇到的疑难问题做统一的整理，为了帮助大家更加顺利地完成这门课程的学习，编写 了这本《数字逻辑电路学习指导》.其中经典问题综合整理主要来自于平时批改作业中 的总结，以及答疑过程中从同学们的反馈中归纳整理.在此特别感谢2020秋数字逻辑 电路O6班的全体同学们的配合与支持 作为信息学院的一员，深切感受到老师们的关爱，衷心感谢各位老师的教导和帮 助.希望尽自己所能，为学院的教学贡献一点点力量.所以特此将这本《数字逻辑电路 学习指导》献给最亲爱的信息学院， 由于个人能力有限，并且在这本学习指导中很多地方是在分享自己的理解和思考， 所以难免会出现一些疏漏、不妥或者错误之处.恳请阅读这本《数字逻辑电路学习指 导》的同学们给予批评指正.也欢迎同学们针对我提出的一些想法和我一起交流探讨： 在此留下个人联系方式Email:wazs98@ustc.edu.cnQQ:2209823112 祝愿学弟学妹们能够顺利完成数字逻辑电路课程学习，取得理想的成绩： 祝愿信息学院的教学工作越来越好： 信息学院1702班信息安全专业高源 2020年11月 6
2020 秋数字逻辑电路 06 班 数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 写给信息学院的学弟学妹们的一封信 亲爱的信息学院的学弟学妹们你们好： 我是高源，来自信息学院 1702 班，信息安全专业.2020 年秋季学期在胡新伟老师 的数字逻辑电路班级 (06 班) 担任课程助教. 在学习数字逻辑电路课程的时候，被这门课程中的迷人的电子学色彩所深深吸引. 学习中注重把握课程特点，并基于课程特点展开深入思考以求得适合自己的学习方法， 这也许是我在学习这门课程的时候还算比较顺利的原因吧. 也想把一些思考和心得和大 家分享，希望能够帮助有需要的同学解决一些学习这门课程中遇到的困难. 有了 2020 年春季学期担任数理方程课程助教的经验后，这学期在开展工作时相对 更加顺利一些. 考虑到有一些学习方法可以分享，以及针对大家在学习这门课程时常常 遇到的疑难问题做统一的整理，为了帮助大家更加顺利地完成这门课程的学习，编写 了这本《数字逻辑电路学习指导》. 其中经典问题综合整理主要来自于平时批改作业中 的总结，以及答疑过程中从同学们的反馈中归纳整理. 在此特别感谢 2020 秋数字逻辑 电路 06 班的全体同学们的配合与支持. 作为信息学院的一员，深切感受到老师们的关爱，衷心感谢各位老师的教导和帮 助. 希望尽自己所能，为学院的教学贡献一点点力量. 所以特此将这本《数字逻辑电路 学习指导》献给最亲爱的信息学院. 由于个人能力有限，并且在这本学习指导中很多地方是在分享自己的理解和思考， 所以难免会出现一些疏漏、不妥或者错误之处. 恳请阅读这本《数字逻辑电路学习指 导》的同学们给予批评指正. 也欢迎同学们针对我提出的一些想法和我一起交流探讨. 在此留下个人联系方式 Email：wazs98@ustc.edu.cn QQ：2209823112. 祝愿学弟学妹们能够顺利完成数字逻辑电路课程学习，取得理想的成绩. 祝愿信息学院的教学工作越来越好. 信息学院 1702 班 信息安全专业 高源 2020 年 11 月 6
数字逻辑电路学习指导 2020秋数字逻辑电路06班 课程综述 2.1简介 电子电路，是指由电子器件和有关无线电元件组成的电路.包括放大、振荡、整流、 检波、调制、频率变换、波形变换等电路，以及各种控制电路.广泛应用于各种电子设 备中 电子电路的功能可以概括为 。能量转换 ·信息处理 我们学习的模拟电子电路所实现的功能主要为能量转换，而数字电子电路实现的 功能主要为信息处理 2.2 课程特点 这门课程的特点可以概括为 。理论性 ·工程性 下面对于课程特点做简要分析 首先我们学习逻辑代数相关的基本知识，从逻辑二值运算开始，引入逻辑函数的 一种表达形式一真值表，进而进一步地引入逻辑函数式以及其他逻辑函数的表达形 式.至此，这门课程的数学基础我们已经基本熟悉.基于此，我们讨论组合逻辑电路和 时序逻辑电路的分析与设计.从某种角度来讲，实际上组合和时序逻辑电路的设计，可 以看作逻辑函数式不同表达形式的转换的过程.比如，组合电路的分析就是从逻辑图到 逻辑式或真值表的转换，而组合电路设计就是从自然语言描述的问题抽象成为逻辑代 数问题，然后用逻辑函数最接近自然语言的表达形式一真值表来转化给定问题.进而 我们通过逻辑函数式不同形式的转化，最后化为逻辑图.时序电路略微复杂，不过总的 来看过程仍然相似， 7
2020 秋数字逻辑电路 06 班 数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 课程综述 2.1 简介 电子电路，是指由电子器件和有关无线电元件组成的电路. 包括放大、振荡、整流、 检波、调制、频率变换、波形变换等电路，以及各种控制电路. 广泛应用于各种电子设 备中. 电子电路的功能可以概括为 • 能量转换 • 信息处理 我们学习的模拟电子电路所实现的功能主要为能量转换，而数字电子电路实现的 功能主要为信息处理. 2.2 课程特点 这门课程的特点可以概括为 • 理论性 • 工程性 下面对于课程特点做简要分析. 首先我们学习逻辑代数相关的基本知识，从逻辑二值运算开始，引入逻辑函数的 一种表达形式——真值表，进而进一步地引入逻辑函数式以及其他逻辑函数的表达形 式. 至此，这门课程的数学基础我们已经基本熟悉. 基于此，我们讨论组合逻辑电路和 时序逻辑电路的分析与设计. 从某种角度来讲，实际上组合和时序逻辑电路的设计，可 以看作逻辑函数式不同表达形式的转换的过程. 比如，组合电路的分析就是从逻辑图到 逻辑式或真值表的转换，而组合电路设计就是从自然语言描述的问题抽象成为逻辑代 数问题，然后用逻辑函数最接近自然语言的表达形式——真值表来转化给定问题. 进而 我们通过逻辑函数式不同形式的转化，最后化为逻辑图. 时序电路略微复杂，不过总的 来看过程仍然相似. 7
数字逻辑电路学习指导 2020秋数字逻辑电路06班 所以，基本逻辑代数理论以及组合、时序电路的分析方法和设计原则是要熟练掌 握的基本理论 但作为一个工程性的学科，在学习时不能只注重理论的学习和理解，要从其工程 性角度出发来思考问题 比如，我们在学习逻辑代数部分，常常研究逻辑函数式的化简.但有时候要思考一 个问题，我们真的一定要化简，或者化到最简吗？化简是我们不变的追求吗？我们选择 化简逻辑函数式，实际上是为了逻辑电路实现的方便，尽量简单的逻辑函数式可以使 得元器件的数量以及连线数量尽可能少，降低成本、减少布局布线所带来的寄生电感 电容、减少焊接出错的可能性等等.但我们可以思考这样一个问题，在研究竞争冒险现 象时，我们提到，一种消除竞争冒险的方法是修改逻辑设计，常用手段是增加冗余项 那么，我们要考虑，这时，从可靠性角度来思考，是不是最简又不是最完美的追求？实 际上，对于模拟电路和数字电路，或者说，对于电子学，我们要有这样一个认识.没有 最好的，只有最合适的，或者说合适的才是最好的，因为有一利就有一弊.所以，在优 化某一个方面时，要问自己，牺牲了什么，可以忍受吗？作为设计者，客户要求是第 位的，所以我们要在各个参数设计中做权衡，达到客户要求的电路才是最好的电路 2.3 学习方法 在明确了课程特点的基础上，我们可以讨论学习这门课程的方法.在这里只做概 述，具体学习方法详见本书各个章节内容 数字电子技术基础这门课，重点就是组合和时序逻辑电路的分析和设计.逻辑代数 基础部分是作为数学基础来介绍，提供分析和设计的工具.而门电路和脉冲产生整形电 路部分则是提供探讨性能的理论基础和手段.模/数和数/模转换则是作为模拟和数字两 部分的衔接，以形成整体的观点. 所以，基本来说，要熟练掌握逻辑代数基础部分的定理、公式，以及逻辑函数的表 达形式及其转化.基于此，可以利用逻辑函数这一有力工具来分析和设计数字电路.学 习这一部分主要是掌握基本方法，并且深入理解其中的精华.比如，一个常见问题是组 合逻辑电路模块的功能扩展，实际上这就是一个组合逻辑电路的设计，只不过可以略 去逻辑抽象和真值表到逻辑式的转化，而且我们要用的不是门电路，而是中规模逻辑 器件.如果这样理解，可能问题就会比较清晰.我们只需要思考，我们的目标是什么， 几个输入，几个输出，控制关系，我们手里有什么，几个输入，几个输出.把输入首先 对应好，每片内部的关系已经有保证，两片之间的关系需要我们思考这个电路的功能 来决定，最后处理输出.这样，我们就完成了这个设计任务 对于门电路和脉冲产生整形电路，可以用模型的观点来思考.门电路的模型可以选 择这一章最初介绍的基本开关电路和基本互补开关电路，思考从这个电路出发，怎样得 到基本二极管电路，有什么问题怎样优化，然后怎样得到电阻负载MOS反相器，最后 得到有源负载的基本MOS反相器.这样，思路可能会比较清晰.脉冲产生和整形电路 8
2020 秋数字逻辑电路 06 班 数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 所以，基本逻辑代数理论以及组合、时序电路的分析方法和设计原则是要熟练掌 握的基本理论. 但作为一个工程性的学科，在学习时不能只注重理论的学习和理解，要从其工程 性角度出发来思考问题. 比如，我们在学习逻辑代数部分，常常研究逻辑函数式的化简. 但有时候要思考一 个问题，我们真的一定要化简，或者化到最简吗？化简是我们不变的追求吗？我们选择 化简逻辑函数式，实际上是为了逻辑电路实现的方便，尽量简单的逻辑函数式可以使 得元器件的数量以及连线数量尽可能少，降低成本、减少布局布线所带来的寄生电感 电容、减少焊接出错的可能性等等. 但我们可以思考这样一个问题，在研究竞争冒险现 象时，我们提到，一种消除竞争冒险的方法是修改逻辑设计，常用手段是增加冗余项. 那么，我们要考虑，这时，从可靠性角度来思考，是不是最简又不是最完美的追求? 实 际上，对于模拟电路和数字电路，或者说，对于电子学，我们要有这样一个认识. 没有 最好的，只有最合适的，或者说合适的才是最好的，因为有一利就有一弊. 所以，在优 化某一个方面时，要问自己，牺牲了什么，可以忍受吗? 作为设计者，客户要求是第一 位的，所以我们要在各个参数设计中做权衡，达到客户要求的电路才是最好的电路. 2.3 学习方法 在明确了课程特点的基础上，我们可以讨论学习这门课程的方法. 在这里只做概 述，具体学习方法详见本书各个章节内容. 数字电子技术基础这门课，重点就是组合和时序逻辑电路的分析和设计. 逻辑代数 基础部分是作为数学基础来介绍，提供分析和设计的工具. 而门电路和脉冲产生整形电 路部分则是提供探讨性能的理论基础和手段. 模/数和数/模转换则是作为模拟和数字两 部分的衔接，以形成整体的观点. 所以，基本来说，要熟练掌握逻辑代数基础部分的定理、公式，以及逻辑函数的表 达形式及其转化. 基于此，可以利用逻辑函数这一有力工具来分析和设计数字电路. 学 习这一部分主要是掌握基本方法，并且深入理解其中的精华. 比如，一个常见问题是组 合逻辑电路模块的功能扩展，实际上这就是一个组合逻辑电路的设计，只不过可以略 去逻辑抽象和真值表到逻辑式的转化，而且我们要用的不是门电路，而是中规模逻辑 器件. 如果这样理解，可能问题就会比较清晰. 我们只需要思考，我们的目标是什么， 几个输入，几个输出，控制关系，我们手里有什么，几个输入，几个输出. 把输入首先 对应好，每片内部的关系已经有保证，两片之间的关系需要我们思考这个电路的功能 来决定，最后处理输出. 这样，我们就完成了这个设计任务. 对于门电路和脉冲产生整形电路，可以用模型的观点来思考. 门电路的模型可以选 择这一章最初介绍的基本开关电路和基本互补开关电路，思考从这个电路出发，怎样得 到基本二极管电路，有什么问题怎样优化，然后怎样得到电阻负载 MOS 反相器，最后 得到有源负载的基本 MOS 反相器. 这样，思路可能会比较清晰. 脉冲产生和整形电路 8
数字逻辑电路学习指导 2020秋数字逻辑电路06班 类似，我们可以从基本门电路构成的施密特触发电路、单稳态电路出发，研究多谐振荡 电路，以及波形分析法的应用.而定时器电路可以看成模型的抽象方式.这一部分，记 住公式很重要.模/数和数/模转换部分，主要是要能从模拟和数字的结合和交互中思考 问题.模拟电路主要从电路本身来研究精度，而数字电路则主要从位数来控制精度，而 转换精度是一个重要参数，所以这要求我们从不同的角度来研究电路.转换速度类似. 2020秋数字逻辑电路06班 9
2020 秋数字逻辑电路 06 班 数字逻辑电路学习指导 2020 秋数字逻辑电路 06 班 类似，我们可以从基本门电路构成的施密特触发电路、单稳态电路出发，研究多谐振荡 电路，以及波形分析法的应用. 而定时器电路可以看成模型的抽象方式. 这一部分，记 住公式很重要. 模/数和数/模转换部分，主要是要能从模拟和数字的结合和交互中思考 问题. 模拟电路主要从电路本身来研究精度，而数字电路则主要从位数来控制精度，而 转换精度是一个重要参数，所以这要求我们从不同的角度来研究电路. 转换速度类似. 9
