摘  要
在電子領(lǐng)域內(nèi),頻率是一種最基本的參數(shù),并與其他許多電參量的測量方案和測量結(jié)果都有著十分密切的關(guān)系。由于頻率信號抗干擾能力強、易于傳輸，可以獲得較高的測量精度。因此,頻率的測量就顯得尤為重要，測頻方法的研究越來越受到重視。
頻率計作為測量儀器的一種，常稱為電子計數(shù)器，它的基本功能是測量信號的頻率和周期頻率計的應(yīng)用范圍很廣,它不僅應(yīng)用于一般的簡單儀器測量,而且還廣泛應(yīng)用于教學(xué)、科研、高精度儀器測量、工業(yè)控制等其它領(lǐng)域。隨著微電子技術(shù)和計算機技術(shù)的迅速發(fā)展，特別是單片機的出現(xiàn)和發(fā)展，使傳統(tǒng)的電子側(cè)量儀器在原理、功能、精度及自動化水平等方面都發(fā)生了巨大的變化，形成一種完全突破傳統(tǒng)概念的新一代側(cè)量儀器。頻率計廣泛采用了高速集成電路和大規(guī)模集成電路，使儀器在小型化、耗電、可靠性等方面都發(fā)生了重大的變化。目前,市場上有各種多功能、高精度、高頻率的數(shù)字頻率計,但價格不菲。
為適應(yīng)實際工作的需要,本次設(shè)計給出了一種較小規(guī)模和單片機(AT89S52)相結(jié)合的頻率計的設(shè)計方案,不但切實可行,而且體積小、保密性強、設(shè)計簡單、成本低、精度高、可測頻帶寬，大大降低了設(shè)計成本和實現(xiàn)復(fù)雜度。頻率計的硬件電路是用Protel繪圖軟件繪制而成，軟件部分的單片機控制程序，是以KeilC做為開發(fā)工具用C語言編寫而成，而頻率計的實現(xiàn)則是選用Ptotues仿真軟件來進(jìn)行模擬和測試。

關(guān)鍵詞：單片機；AT89S52；頻率計；C語言
 
ABSTRACT
In the electronic field, frequency is a kind of most basic parameter, and all there are close relations in the measurement schemes of many other electric parameters and result of measuring. Because the signal anti-interference ability of frequency is strong, easy to transmit, can obtain higher measurement precision. So, the measurement of frequency seems particularly important, the research of the method is being paid attention to.
The Frequency meter, as one kind of the measuring instrument, often called the electronic counter, its basic function is that frequency and application of cycle Frequency meter of measuring the signal are in a very large range, it not only applies to general simple instrument measurement but also apply to other fields such as teaching, scientific research, high-accuracy instrument measuring, industrial control extensively. With the rapid development of microelectric technique and computer technology, especially appearance and development of the one-chip computer, the instruments have all changed enormously in such aspects as principle, function, precision and automatic level to enable the traditional electronic side amount, form a kind of side amount instrument of new generation that totally broke through the traditional concept. The Frequency meter has adopted the high-speed integrated circuit and large scale integrated circuit extensively, make the instrument change greatly in such aspects as miniaturize, power consumptive, dependability. At present, there are various digital Frequency meter of multi-function, high precision, high frequency on the market, but the price is high.
In order to meet the need of the real work, design and provide one this time The design plan of Frequency meter combining with one-chip computer (AT89S52) on a small scale, not only feasible, and small, of good security, design simply, with low costs, the precision is high, can examine the bandwidth frequently, have reduced the design cost and realized complexity greatly. The hardware circuit of the Frequency meter is drawing with Protel mapping software, the one-chip computer control procedure of the software part, regarded KeilC as the developing instrument to write in C language, but the realization of the Frequency meter was to select to carry on imitating and test with Protues artificial software.

Key Words：single chip computer; AT89S52; frequency meter; C language 
目  錄
1 緒 論 1
1.1 課題的引入 1
1.2 產(chǎn)生背景 1
1.3 國內(nèi)外研究現(xiàn)狀 2
1.4 單片機頻率計設(shè)計的目的及意義 2
2 AT89S52單片機介紹及其發(fā)展概況 4
2.1 單片機的介紹 4
2.1.1 單片機概述 4
2.1.2 單片機的發(fā)展 5
2.1.3 單片機的特點及應(yīng)用 5
2.2 AT89S52系列單片機 6
2.2.1 AT89系列單片機 6
2.2.2 AT89S52系列單片機的基本結(jié)構(gòu) 7
3 頻率計總體方案設(shè)計 10
3.1 頻率計設(shè)計原理 10
3.1.1 頻率檢測實現(xiàn)方法 10
3.1.2 頻率計測頻原理 11
3.2 設(shè)計思路及方法 11
3.2.1 頻率計方案概述 12
3.2.2 頻率計的量程自動切換 12
4 系統(tǒng)的硬件設(shè)計 14
4.1 時鐘信號發(fā)生器 14
4.2 AT89S52 控制寄存器 15
4.2.1 AT89S52中斷控制系統(tǒng) 15
4.2.2 AT89S52定時/計數(shù)器的控制 17
4.3 LCD1602顯示電路 18
4.3.1 LCD1602的主要技術(shù)參數(shù)及接口說明 19
4.3.2 控制器接口及時序 19
4.3.3 頻率計硬件電路整體設(shè)計 20
5 系統(tǒng)的軟件設(shè)計 22
5.1 Keil C簡介 22
5.2 頻率計程序的建立過程 23
5.3 軟件功能模塊設(shè)計 27
5.3.1 LCD初始化設(shè)置模塊 28
5.3.2 浮點數(shù)到ASCII碼轉(zhuǎn)換模塊 28
5.3.3 定時/計數(shù)器初始化模塊 29
5.3.4 定時器中斷服務(wù)模塊子程序 29
6 系統(tǒng)的模擬及仿真 31
6.1 Proteus ISIS簡介 31
6.1.1 Proteus ISIS的概況簡介及特點 31
6.1.2 Proteus ISIS的運行概況 31
6.1.3 用Proteus 軟件虛擬單片機實驗的優(yōu)點 32
6.2 系統(tǒng)的模擬與仿真過程 33
6.3 頻率計系統(tǒng)仿真分析 37
結(jié)束語 41
致謝 42
參考文獻(xiàn) 43