目录目录......................................................................I第1章引言............................................................11.1设计概述............................................................11.2设计目标与意义......................................................11.3频率计的发展现状....................................................21.4FPGA的介绍..........................................................21.5VHDL简介............................................................31.4章节安排.............................................................4第2章方案论证与选型....................................................52.1设计任务分析........................................................52.2方案论证与选择......................................................52.2.1方案一：采用小规模数字集成电路制作..............................52.2.2方案二：采用单片机为控制中心进行测频............................52.2.3方案三：采用FPGA作为控制中心的数字频率计.......................62.3方案确定............................................................6第3章数字频率计基本原理以及实现方法....................................73.1数字频率计的基本原理................................................73.2数字频率计的实现方法................................................73.3数字频率计电路总体框图..............................................8第4章硬件设计..........................................................94.1设计阐述............................................................94.2EP2C5T144芯片的说明.................................................94.2.1EP2C5T144概述...................................................94.2.2硬件设计.......................................................101、电源电路..........................................................102、时钟电路..........................................................113、复位电路..........................................................124、配置/下载接口.....................................................125、配置电路..........................................................136、LED电路...........................................................148、扩展板接口..........................