基于 CPLD 的频率测量计摘 要本文主要论述了利用 CPLD 进行测频计数，单片机实施控制实现等精度频率计的设计过程。该频率计利用等精度的设计方法，克服了基于传统测频原理的频率计的测量精度随被测信号频率的下降而降低的缺点。等精度的测量方法不但具有较高的测量精度，而且在整个频率区域保持恒定的测试精度。该频率计利用 CPLD 来实现频率的测量计数。利用单片机完成整个测量电路的测试控制、数据处理和显示输出。本文详细论述了硬件电路的组成和单片机的软件控制流程。其中硬件电路包括键控制模块、显示模块、输入信号整形模块以及单片机和 CPLD 主控模块。设计器件采纳 Atmel 公司的单片机 AT89C51 和 Altera 公司的 MAX7000 系列 EPM7128SLC84-15 芯片。键控制模块设置 1 个开始键和 3 个时间选择键，键值的读入采纳一片 74LS165 来完成；显示模块用 8 只 74LS164 完成 LED 的串行显示；被测信号经限幅后由两级直接耦合放大器进行放大，再经施密特触发器整形后输入 CPLD；标准频率采纳 40MHz 有源晶振动实现；单片机软件用汇编语言编写，软件模块对应于硬件电路的每一个局部，还包括局部数据计算和转换模块。关键词：单片机，CPLD，频率计，测频，等精度THE DESIGN OF FREQUENCY MEASUREMENT BASED ON CPLDAbstractThe reach pape rmainly discusses the design process of equal-accuracy frequency meter that uses CPLD to count the frequency measurement and frequency meter is also controled by single chip computer. The frequency meter makes use of equal-accuracy design that can overcome the disadvantage of traditional measuring principle, which precision declines as measured signal frequency does. The equal-accuracy measurement not only has higher measuring precision, but also can keep invariable measuring precision in whole area of frequency.This frequency meter uses CPLD to realize the measuring count of frequency. Single chip computer completes the test control、data processing and display output of the system.This essay discusses the compose of hardware circuit and software control flow of single chip...
