定时器实现时钟送数码管显示+独立键盘设置时间
前言··························································································································2 任务书······················································································································3· 1.方案选择
1.1.键盘设计············································································································4 1.2.门电路设计·········································································································5 1.3.显示电路·············································································································5 2.硬件电路及参考程序
2.1基于proteus仿真的硬件电路···········································································7 2.2参考程序·············································································································8 3试验调试
3.1 硬件电路的连接·······························································································14 3.2.硬件电路的调试································································································14
4试验结论···········································································································14 5心得体会···········································································································15 6参考文献及元器件引脚图
6.1参考文献···········································································································20 6.2 元器件引脚图····································································································21 6.3 AT89C51的若干时序·······················································································23 6.4硬件电路图·········································································································24
6.5元器件清单·········································································································26
前 言
随着时代科技的迅猛发展，微电子学和计算机等现代电子技术的成就给传统的电子测量与仪器带来了巨大的冲击和革命性的影响。常规的测试仪器仪表和控制装置被更先进的智能仪器所取代，使得传统的电子测量仪器在远离、功能、精度及自动化水平定方面发生了巨大变化，并相应的出现了各种各样的智能仪器控制系统，使得科学实验和应用工程的自动化程度得以显著提高。
基于单片机课程的学习，本小组成员利用单片机实现时钟的显示，利用键盘和门电路控制时间的调整，充分利用单片机的资源和空间，较大限度的实现了功能。
在课程设计的过程中，我们发现了许多实际应用中所遇到的问题，在调试的过程中学到了更多的东西。让我们充分的认识道学以致用的价值！
任务书
电子时钟主要由显示模块、校时模块和时钟运算模块三大部分组成。其中校时模块和时钟运算模块要对时、分、秒的数值进行操作，并且秒计算到60时，要自己清零并向分进1；分计算到60时，要自己清零并向时进1；时计算到24时，要清零。这样，才能循环记时。
设计要求：
1） 2）
设计一款电子时钟，用共阴极七段数码管显示时间；
6个数码管分别显示时、分、秒；可以利用四个键盘调整时间，小时
键每次调整一小时，分钟用两个键调整十位和各位，秒钟键调整秒显示的十位；
3） 4）
硬件电路的调试； 写出详细的课设报告。
1方案的选择
1.1 键盘的设计
考虑到时间误差的存在以及调整时间的方便性，采用独立式键盘。 提高CPU的工作效率，采用中断工作方式
四个键盘接于P1口，用74ls21与门接于外部中断0，实现了调整时间的快速性，当四个键盘有中断发生，首先判断四个键哪个按下，向CPU发一个中断请求信号，然后调用相应的中断程序。参考电路如下：
键盘的工作过程可分为两步：第一步是CPU首先检测键盘上是否有按键被按下，第二步是识别哪一个减按下。检查键盘上有无键按下可采用查询工作方式、定时扫描工作方式和中断工作方式。
查询工作方式（例如用8155扩展I/O组成的行列式键盘）：
键盘上有无键按下是有列线送出全扫描字，然后读入行线状态来识别的。其方法是PA口输出00H，即所有列线置成低电平，然后将行线电平状态读入累加
器A中，如果有键按下，总会有一根行线拉置低电平，从而使行输入状态不全为“1”。键盘中哪一个键按下是有列线逐列置低电平后，检查行输入状态，称为逐列扫描。方法是：从PC口读入行线状态，如果全为“1”，则所按下之键不在此列，如果不全为“1”，则在此列，并且是与“0”电平行线相交的交点上的那个键。
1.2 门电路的设计
为了达到调整时间的快速性与准确性，采用中断方式，四个键盘采用与门芯片74LS21。当四个键盘有一个按下后就会向CPU申请中断。 1.3显示电路
显示采用led动态显示方式，共阴极端由P2口线控制，分为段选线和位选线，利用人的视觉停留达到显示的效果，段选线控制字符选择，位选线控制显示位的亮或暗。从段选线I/O口上按位次分别送显示字符的段选码，在位选控制口也按相应的次序分别选通相应的显示位（共阴极送低电平，共阳极送高电平），选通位就显示相应字符，并保持几毫秒的延时，为选通不显示字符（保持熄灭）。这样，对各位显示就是一个循环过程。从计算机工作来看，在一个瞬间只有一位显示字符，而其他位都是熄灭的。但由于人的视觉停留，这种动态变化是察觉不到的。从效果上看，各位显示器能连续而稳定地显示不同的字符。