51最基础简单易懂的单片机，差不多一个月的时间，断断续续地学习，终于算是学完了，下个目标是飞思卡尔s12x和k60 也就是ARM crotex-M4架构. 51最核心的部分，我觉得是中断的使用，一个项目离不开中断，还有就是串口的理解，还有就是IIC通信。

以 电子时钟 为结尾篇，附上代码。代码有些不怎么完美。但终究是差不多写出来了。结合了IIC通信，中断定时器的使用，键盘使用，还有液晶的显示。

#include

sbit RS = P2^7;

sbit RW = P2^6;

sbit E = P2^5;

sbit Sda = P2^0;

sbit Scl = P2^1;

sbit keyleft = P1^0;

sbit keyup = P1^1;

sbit keydown = P1^2;

sbit keyright = P1^3;

unsigned char sec=0,min=0,hour=0;

unsigned char Year[20]=" 2012.10.1 ";

unsigned char i;

unsigned int times = 0;

unsigned char countleft = 0,countright = 0;

unsigned char busycheck();

static void Start(void)

{

Sda = 1;

Scl = 1;

Sda = 0;

}

static void Stop(void)

{

Sda = 0;

Scl = 1;

Sda = 1;

}

static unsigned char Respons(void)

{

unsigned char OverTime = 0; //超时

unsigned char TempFlag = 0;

OverTime = 0;

Sda = 1; //释放数据线

Scl = 1;

while(1)

{

if(Sda) //应答信号没来

{

if(OverTime++ > 200)

{

TempFlag = 0; //应答信号长时间没有来，认为无应答

break;

}

}

else

{

TempFlag = 1; ///检测到应答信号

break;

}

}

Scl = 0;

return TempFlag;

}

static void NoRespons(void) //非应答

{

Sda = 1; //释放数据线

Scl = 1;

Scl = 0;

}

static void WriteByte(unsigned char temp)

{

unsigned char i;

Scl = 0;

for(i = 0;i < 8;i++)

{

Sda = temp & 0x80;

temp <<= 1;

Scl = 1; //scl拉高，准备写数据

Scl = 0; //scl拉低，写数据完成

}

}

static unsigned char ReadByte(void)

{

unsigned char i;

unsigned char x = 0;

for(i = 0;i < 8;i++)

{

Scl = 1;

x <<= 1;

x |= (unsigned char)Sda;

Scl = 0;

}

return x;

}

void WriteIIC(unsigned char device,unsigned char parameter,unsigned char temp)

{

Start();

WriteByte(device);

if(Respons())

{

WriteByte(parameter);

if(Respons())

{

WriteByte(temp);

if(Respons())

{

Stop();

}

else

{

Stop();

}

}

else

{

Stop();

}

}

else

{

Stop();

}

}

unsigned char ReadIIC(unsigned char device,unsigned char parameter)

{

unsigned char x;

Start();

WriteByte(device);

if(Respons())

{

WriteByte(parameter);

if(Respons())

{

Start();

WriteByte(device | 0x01);

if(Respons())

{

x = ReadByte();

NoRespons();

Stop();

}

else

{

Stop();

}

}

else

{

Stop();

}

}

else

{

Stop();

}

return x;

}

void writecmd(unsigned char cmd)

{

while(busycheck());

RS = 0;

RW = 0;

E = 1;

P0 = cmd;

E = 0;

}

void writedata(unsigned char dat)

{

while(busycheck());

RS = 1;

RW = 0;

E = 1;

P0 = dat;

E = 0;

}

unsigned char busycheck()

{

P0 = 0xff;

RS = 0;

RW = 1;

E = 0;

E = 1;

return(P0 & 0x80);

}

void writedate(unsigned char add,unsigned char date)

{

unsigned char shi,ge;

shi = date/10;

ge = date%10;

writecmd(0x80+0x40+add);

writedata(0x30+shi);

writedata(0x30+ge);

}

void Init()

{

writecmd(0x38);//显示模式

writecmd(0x08);//关屏

writecmd(0x01);//清屏

writecmd(0x06);//设置光标右移

writecmd(0x0c);//显示，无标 闪烁

writecmd(0x80);

for(i = 0;i < 20;i++)

writedata(Year[i]);

writecmd(0x80+0x40+6);

writedata(':');

writecmd(0x80+0x40+9);

writedata(':');

sec = ReadIIC(0xa0,0);

min = ReadIIC(0xa0,2);

hour = ReadIIC(0xa0,4);

writedate(10,sec);

writedate(7,min);

writedate(4,hour);

TMOD = 0x02;

TH0 = 6;

TL0 = 6;

EA = 1;

ET0 = 1;

TR0 = 1;

}

void delay()

{

unsigned char x = 2000;

while(x--);

}

void keyscan()

{

if(!keyleft)

{

delay();

if(!keyleft)

{

TR0 = 0;

if(countleft == 0)

{

countleft++;

writecmd(0x80+0x40+10);

writecmd(0x0f);

}

else

if(countleft == 1)

{

countleft++;

writecmd(0x80+0x40+7);

}

else

if(countleft == 2)

{

countleft++;

writecmd(0x80+0x40+4);

}

else

if(countleft == 3)

{

TR0 = 1;

writecmd(0x0c);

countleft = 0;

}

else

{

}

}

else

{

}

}

else

{

}

if(!keydown)

{

delay();

if(!keydown)

{

if(countleft == 1)

{

sec--;

if(sec == 60)

sec = 0;

writedate(10,sec);

WriteIIC(0xa0,1,sec);

writecmd(0x80+0x40+10);

}

else

if(countleft == 2)

{

min--;

if(min == 60)

min = 0;

writedate(7,min);

WriteIIC(0xa0,2,min);

writecmd(0x80+0x40+7);

}

else

if(countleft == 2)

{

hour--;

if(hour == 24)

hour = 0;

writedate(4,hour);

WriteIIC(0xa0,3,hour);

writecmd(0x80+0x40+4);

}

else

{

}

}

else

{

}

}

else

{

}

if(!keyright)

{

delay();

if(!keyright)

{

if(countleft == 1)

{

sec++;

if(sec == 60)

sec = 0;

writedate(10,sec);

writecmd(0x80+0x40+10);

}

else

if(countleft == 2)

{

min++;

if(min == 60)

min = 0;

writedate(7,min);

writecmd(0x80+0x40+7);

}

else

if(countleft == 2)

{

hour++;

if(hour == 24)

hour = 0;

writedate(4,hour);

writecmd(0x80+0x40+4);

}

else

{

}

}

else

{

}

}

else

{

}

}

void main()

{

Init();

while(1)

{

keyscan();

}

}

void Time0(void) interrupt 1

{

times++;

if(times == 3686)

{

times = 0;

sec++;

if(sec == 60)

{

sec = 0;

min++;

if(min == 60)

{

min = 0;

hour++;

if(hour == 24)

{

hour = 0;

}

writedate(4,hour);

WriteIIC(0xa0,3,hour);

}

writedate(7,min);

WriteIIC(0xa0,2,min);

}

writedate(10,sec);

WriteIIC(0xa0,1,sec);

}

}