目 录
1 引言 ..................................................................1
1.1 数字频率计的发展和意义.............................................1
1.2 数字频率国内外的发展形势...........................................2
2 系统总体设计 ..........................................................3
2.1 系统设计要求.......................................................3
2.2 测频方法...........................................................3
2.3 系统设计思路.......................................................3
2.4 系统设计框图.......................................................4
3 系统硬件设计 ..........................................................5
3.1 单片机模块.........................................................5
3.1.1 AT89C52 介绍..................................................5
3.1.2 单片机引脚分配 ..............................................6
3.1.3 复位电路 .....................................................6
3.1.4 定时/计数器 ..................................................6
3.2 放大整形模块.......................................................8
3.2.1 与非门 74LS00.................................................8
3.2.2 放大整形模块原理图 ...........................................8
3.3 分频模块...........................................................9
3.3.1 分频器 74LS161 芯片 ...........................................9
3.3.2 多路选择器 74LS151 芯片 ......................................10
3.3.3 分频模块原理图 ..............................................12
3.4 显示电路..........................................................12
3.4.1 频率数值显示电路 ............................................12
3.4.2 频率数值单位显示电路 ........................................13
4 系统软件设计 .........................................................15
4.1 开始..............................................................15
4.2 初始化模块........................................................16
4.3 频率测量模块和量程自动切换模块....................................16
4.4 显示模块..........................................................17
4.5 延时模块..........................................................18
5 数字频率计仿真 .......................................................19
5.1 放大整形电路仿真 ..................................................19
5.1.1 仿真软件 MULTISIM 10.0 仿真整形电路..........................19
5.1.2 仿真放大整形电路 ............................................19
5.2 频率计仿真........................................................22
5.2.1 用 KEIL 软件 .................................................22
5.2.2 使用软件 Proteus 仿真频率计 ..................................23
5.2.3 频率计仿真运行调试 ..........................................25
6 结论 ...................................................................30
