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目录 ·································································································································································· 1 1 题目背景与意义 ········································································································································· 2 2 设计题目介绍 ············································································································································· 3 2.1设计目的 ········································································································································ 3 2.2设计意义 ········································································································································ 3 3 系统总体框架 ············································································································································· 4 4 系统硬件设计 ············································································································································· 5 4.1单片机选型 ···································································································································· 5 4.1.1 AT89C51功能介绍： ············································································································ 5 4.1.2晶振电路 ································································································································· 6 4.1.3复位电路 ································································································································· 6 4.2 A/D转换电路 ································································································································ 7 4.2.1 ADC0809功能介绍： ············································································································ 7 4.2.2 A/D转换电路图 ····················································································································· 8 4.3 D/A转换电路 ································································································································ 9 4.3.1 DAC0832功能 ······················································································································· 9 4.3.2 D/A转换电路图 ··················································································································· 10 4.5调理电路 ······································································································································ 10 4.6 报警指示灯电路 ························································································································· 11 4.7 键盘、显示控制电路 ················································································································· 12 4.7.1键盘电路 ······························································································································· 12 4.7.2显示电路 ······························································································································· 12 5 系统软件设计 ··········································································································································· 14 5.1 主程序框图 ································································································································· 14 5.2数据程序框图 ······························································································································ 15 5.3 键盘程序框图 ····························································································································· 16 5.4显示程序框图 ······························································································································ 17 6 总结 ··························································································································································· 18 7总体设计电路原理图 ······························································································································· 19
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1 题目背景与意义
在自动控制系统的实际工程中，经常需要检测被测对象的一些物理参数，如温度、流量、压力、速度等，这些参数都是模拟信号的形式。它们要由传感器转换成电压信号，再经A/D转换器变换成计算机能够处理的信号。同样，计算机控制外设，如电动调节阀、模拟调速系统时，就需要将计算机输出的数字信号经过D/A转换器变换成外设能接受的模拟信号。 本次《计算机控制系统》课程设计的目的就是让同学们在理论学习的基础上，通过完成一个涉及MCS-51单片机A/D和D/A多种资源应用并具有综合功能的小系统目标板的设计与编程应用，使我们不但能够将课堂上学到的理论知识与实际应用结合起来，而且能够对电子电路、电子元器件、等方面的知识进一步加深认识，同时在系统设计、软件编程、相关仪器设备的使用技能等方面得到较全面的锻炼和提高。帮助同学们增进对单片机的感性认识，加深对单片机理论方面的理解，从而更好的掌握单片机的内部功能模块的应用以及A/D和D/A功能的实现。使学生了解和掌握单片机应用系统的软硬件设计过程、方法及实现，为以后设计和实现单片机应用系统打下良好基础。
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2 设计题目介绍
2.1设计目的
设计一个基于单片机的具有A/D和D/A功能的信号测控装置。要求该信号测控装置能够接入典型传感器、变送器信号，同时可输出标准电压/电流信号。并满足抗干扰、通用性、安全性、性价比等原则性要求。标准电压/电流信号定为：0～5V/4～20mA (0～20mA)
2.2设计意义
通过设计此信号测控装置，加深对控制系统的理解，全面掌握所学的知识并灵活运用起来。
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3 系统总体框架
模拟量输入
模数转换模块 数模转换模块 键盘模块 模拟量输出
8051 声光报警 稳压电源 显示模块
图1 系统总体框架图
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4 系统硬件设计
4.1单片机选型
由于80C51单片机采用的是CHMOS工艺，高速度、高密度、低功耗，具有
价格便宜、易上手、抗干扰能力强、稳定性好等优点，且满足我所设计的系统要求的条件，所以此次设计选用80C51单片机作为处理核心。其结构如图2所示：
U1119XTAL1P0.0/AD0P0.1/AD1P0.2/AD2P0.3/AD3P0.4/AD4P0.5/AD5P0.6/AD6P0.7/AD7P2.0/A8P2.1/A9P2.2/A10P2.3/A11P2.4/A12P2.5/A13P2.6/A14P2.7/A15P3.0/RXDP3.1/TXDP3.2/INT0P3.3/INT1P3.4/T0P3.5/T1P3.6/WRP3.7/RD39383736353433322122232425262728101112131415161718XTAL29RST293031PSENALEEA12345678P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.780C51 图2 80C51结构
4.1.1 AT89C51功能介绍：
Vss(20脚) : 接地。
VCC（40脚）: 主电源+5V。
XTAL1（19脚）:接外部晶体的一端。在片内它是振荡电路反相放大器的输入端。对于CHMOS单片机，此引脚作为驱动端。
XTAL2（18脚）: 接外部晶体的另一端。在片内它是一个振荡电路反相放大器的输出端，振荡电路的频率是晶体振荡频率。对于CHMOS单片机，此引脚应悬浮。
RST（9脚）: 单片机刚接上电源时，其内部各寄存器处于随机状态，在该脚输入24个时钟周期宽度以上的高电平将使单片机复位（RESET）。
PSEN（29脚）: 外ROM读选通信号。
ALE/PROG（30脚）: 地址锁存允许/片内EPROM编程脉冲。 EA/VPP（31脚）: 当EA端输入高电平时，CPU从片内程序存储器地址0000H单元开始执行程序。当地址超出4KB时，将自动执行片外程序存储器的程序。当EA输入低电平时，CPU仅访问片外程序存储器。
输入/输出引脚：
（1）P0.0—P0.7 (39脚—32脚) 作为数据总线 （2）P1.0—P1.7 （1脚—8脚） （3）P2.0—P2.7 （26脚—21脚）
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