51单片机入门程序——秒表程序示例

下午自学了一下单片机的前几章的知识，理解了数码管的显示原理以及静态显示和动态扫描的编程方法。其中，比较重要的几个概念有：数码管公共端类型(共阴极、共阳极)、位选(决定多位数码管中哪一位显示)、段选(决定数码管显示的数字)，另外还有锁存器(教材P36，可通过控制锁存端来改变数据输出的状态)。

上周单片机实验课的内容是编一个秒表，在4位数码管中分别显示分和秒还有分秒，即最多可显示“9:59.9”。这里我用两个键实现了秒表的启动/暂停和清零功能，代码如下：

#include <reg51.h>
#define uint unsigned int
#define uchar unsigned char
sbit S1 = P1^3;
sbit S2 = P1^1;
sbit S3 = P1^2;
sbit S4 = P1^0;
sbit beep = P2^7;
sbit a = P0^0;
sbit b = P0^1;
sbit c = P0^2;
sbit d = P0^3;
sbit e = P0^4;
sbit f = P0^5;
sbit g = P0^6;
sbit p = P0^7;
sbit key1 = P1^4;
sbit key2 = P1^5;
sbit key3 = P3^6;
sbit key4 = P3^7;
uchar num,kms,sec,min;
uchar code N[10] = {0xc0, 0xf9 ,0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x90}; //0, 1, 2, 3, ...8, 9
uchar code Z[10] = {0x40, 0x79 ,0x24, 0x30, 0x19, 0x12, 0x02, 0x78, 0x00, 0x10}; //0., 1., 2., ... 8., 9.

void delayms(uint xms)
{
uint i,j;
for(i = xms; i > 0; i--)
for(j = 110; j > 0; j--);
}

void init()
{
TMOD = 0x01;
TH0 = 0x3c;
TL0 = 0xb0;
S3 = 1;
S1 = S2 = S4 = 0;
P0 = N[0];
delayms(5);

S3 = 0;
S1 = S2 = S4 = 1;
P0 = Z[0];
delayms(5);

EA = 1;
TR0 = 0;
ET0 = 1;
kms = sec = min = 0;
}

void display()
{
uchar shi, ge;
if(kms >= 0)
{
S4 = 0;
S1 = S2 = S3 = 1;
P0 = N[kms];
}
delayms(5);
if(sec >= 0)
{
shi = sec/10;
ge = sec%10;

S3 = 0;
S1 = S2 = S4 = 1;
P0 = Z[ge];
delayms(5);

S2 = 0;
S1 = S3 = S4 = 1;
P0 = N[shi];
}
delayms(5);
if(min >= 0)
{
S1 = 0;
S2 = S3 = S4 = 1;
P0 = N[min];
}
delayms(5);
}

void keyscan()
{
if(key1 == 0)
{
delayms(10);
if(key1 == 0)
{
while(!key1);
TR0 = ~TR0;
}
}
if(key2 == 0)
{
delayms(10);
if(key2 == 0)
{
min = sec = kms = 0;
while(!key1);
}
}
}

main()
{
init();
while(1)
{
keyscan();
display();
}
}

void T0_time() interrupt 1
{
TH0 = 0x3c;
TL0 = 0xb0;
num++;
if(num == 2)
{
num = 0;
kms++;
if(kms == 10)
{
kms = 0;
sec++;
if(sec == 60)
{
sec = 0;
min++;
if(min == 10)
{
TR0 = 0;
min = 9;
sec = 59;
kms = 9;
}
}
}
}
}

程序通过“Keil uVision4”调试，大家也可以在板子上运行一下试试。

注意：需要根据板子的端口定义相关变量，不要不分青红皂白就直接使用我的程序哈。

最后上个图，第一次做单片机，希望以后还有时间可以做更深入的更好玩的东西。