目录引言··································································3 1 设计意义及要求·····················································41.1 设计意义······················································41.2 设计要求······················································4 2 方案设计 ·······················································52.1 设计思路·····················································62.2 方案设计·····················································62.2.1 设计方案一··············································72.2.2 设计方案二··············································72.3 方案比较·····················································81 3 部分电路设计······················································93.1 数码管显示单元···············································93.2 计时单元······················································113.3 片选单元······················································123.4 脉冲产生模块··················································133.5 红、绿、黄灯的控制············································144 仿真操作步骤及使用说明··················...