摘要采用自上向下的设计方法,设计了基于复杂可编程逻辑器件的数字频率计。以AT89C51单片机作为系统的主控部件，完成电路的测试信号控制、数据运算处理、键盘扫描和控制数码管显示。用VHDL语言编程，由CPLD(Complex Programmable Logic Device)完成各种时序控制及计数功能。该系统具有结构紧凑、可靠性高、测频范围宽和精度高等特点。关键词 可编程逻辑器件 CPLD 等精度测量法 单片机 VHDLAbstactWith the adoption of the top-down design method and AT89C51 SCMC (Single Chip Mico Computer) as the master control component of the system,the circuit test signalcontrolling,data operation processing,keyboard scanning,and nixie tube display as well were completed by the digital cymometer.A CPLD programmed by VHDL,realized various sequence control and count functions.The system is characterized by impact structure,high reliability,high precision,and wide frequency-test-range. Key Words programmable logic component CPLD measures mensuration single chip mico computer VHDL 目录摘要…………………………………………………………………………………….英文摘要……………………………………………………………………………….绪论…………………………………………………………………………………….Ⅰ第一章 设计方案选择………………………………………………………………….11.1 频率测量模块………………………………………………………………………11.2 周期测量模块………………………………………………………………………31.3 脉冲宽度测量模块…………………………………………………………………41.4 占空比测量模块……………………………………………………………………41.5 标准频率发生电路…………………………………………………………………41.6 小信号处理部分……………………………………………………………………4第二章 基本测量原理与理论误差分析……………………………………………….62.1 等精度频率/周期测量技术………………………………………………………...62.2 预置门时间信号与闸门时间信号…………………………………………………72.3 高精度恒误差周期测量法…………………………………………………………72.4 脉冲宽度测量理论误差分析………………………………………………………72.5 周期脉冲信号占空比测量误差分析………………………………………………7第三章 方案的实现…………………………………………………………………….93.1 稳压电源设计………………………………………………………………………93.2 测量控制电路………………………………………………………………………93.3 输入信号处理部分………………………………………………………………..103.4 小信号处理部分…………………………………………………………………..103.5 标准频率方波发生电路…………………………………………………………..103.6 显示器电路………………………………………………………………………..113.7 实际数字测量部分………………………………………………………………..14第四章 单片机控制与运算程序的设计……………………………………………...184.1 主流程图…………………………………………………………………………..184.2 VHDL源程序………………………………………………………………………19第五章 结束语………………………………………………………………………...25致谢…………………………………………………………………………………….26参考文献……………………………………………………………………………….27……