摘要数字频率计是一种用于测量周期信号在单位时间内变化的物理量、显示被测 信号频率的工具。本课题主要设计了基于等精度原理的频率计，该频率计系统由 CPLD 部分和单片机部分构成，选用 MAX II 系列 CPLD 芯片 EPM240GT100C5 与 STC89C52RC 单片机。CPLD 部分使用 VHDL 语言编写各个功能模块，然后生成特定 功能元器件，最终绘制成原理图。整个 CPLD 软件设计在 Quartus II 平台上完成， 借助仿真器下载到 CPLD 芯片中，实现计数、锁存等功能，并且将计数值输出到单 片机接口。单片机部分使用 Keil 软件编写 C 语言，实现时序控制、数值计算、数 码管显示的功能。该系统兼有单片机的灵活控制性和 CPLD 的现场可编程性，同时 在较宽的频率范围内具有较高且相等的测频精度。68447

毕业论文关键词 数字频率计 等精度测量 单片机 CPLD

Title Equal precision frequency meter based on single-ship  microcomputer and CPLD

Abstract

Digital frequency meter is a kind of tool used for measuring the change numbers of the periodic signal in unit time, and displaying the frequency of the measured signal. This project is mainly designed of the frequency meter based on the principle of equal accuracy. The frequency meter system consists of the part of CPLD and single chip microcomputer(SCM), using EPM240GT100C5 of the MAX II series CPLD chip and STC89C52RC SCM. The part of CPLD uses VHDL language to get each functional module, then it generates a specific function components, and finally gets the schematic diagram (SCH). On the platform of Quartus II, the CPLD program is designed to realize the function such as counting , latches. With the help of the simulator, the program is downloaded into CPLD chip, then the CPLD outputs the data to the SCM interface. MCU part uses C language to write, using Keil software to realize the function such as sequential control , numerical calculation and digital tube display. This system has both flexible control of single chip microcomputer and programmable performance of CPLD, and at the same time, it has high and equal frequency accuracy in a wide frequency range.

Keywords digital frequency meter precision measurement single-chip microcomputer CPLD

目 次

1 绪论 1

1.1 数字频率计概述 1

1.2 数字频率计的发展状况及研究概况 1

1.3 研究背景及研究意义 1

1.4 本课题的主要内容 2

2 系统设计原理 2

2.1 直接测频法 2

2.2 等精度测频法 4

3 硬件电路分析 5

3.1 单片机部分 5

3.2