rs485.c

这是一个有关C8051F020单片机的实验教学材料,相信对于单片机的研究人员会有很大的帮助.

//-----------------------------------------------------------------------------
// 版权归新华龙电子公司所有
//-----------------------------------------------------------------------------
//
//文件名：	RS485.c
//
//编写人：	LC
//
//编写时间：2005/03/10
//
//目标器件: C8051F02x
//
//编译工具: Silicon Laboratories IDE
//
//程序说明:	此程序用UART1外扩MAX485实现RS-485通信，运行前将TX1和P00 短接，RX1和
//			P01短接，当接收到一个数据后，再将接收到的数据送出。
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f020.h>                 /*SFR定义*/
#include <intrins.h>

//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------

#define SYSCLK       11059200          /*系统频率*/
#define BAUDRATE     9600              /*波特率*/
sbit	BUZ = P3^5;
sbit	P32 = P3^2;						/*接收/发送控制*/
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void SYSCLK_Init (void);
void PORT_Init (void);
void UART1_Init (void);
void UART1_ISR (void);

bit	ReceiveBit;
unsigned char temp;

/*延时子程序*/
void delay(unsigned int m)
{
	unsigned int n;
	n=0;
	while(n < m)
	{n++;}
	return;
}
//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void) {
   unsigned char i;
   WDTCN = 0xde;                       /*关看门狗*/
   WDTCN = 0xad;
   ReceiveBit=0;
   SYSCLK_Init ();                     /*初始化系统时钟*/
   PORT_Init ();                       /*初始化I/O口*/
   UART1_Init ();                      /*初始化UART1*/
   EA = 1;                             /*开总中断*/
   EIE2  |= 0x40;                      /*UART1中断*/
   P32 = 0;								/*接收模式*/
	while(1){
		while (ReceiveBit==1) {			/*接收到一个数据*/
			EIE2  &= 0xbf;              /*无效UART1中断*/
			EA=0;						/*关总中断*/
			ReceiveBit=0;				/*清接收位*/
			P32=1;						/*发送模式*/
			delay(60000);				/*延时*/
			SBUF1=temp;
			while(SCON1&0x02==0);		/*发送中断模式是否产生*/
			SCON1 = SCON1&0xfd;			/*清发送中断标志*/
			delay(60000);				/*延时*/
			P32 = 0;
			BUZ=0;						/*蜂鸣器响*/
			for(i=0; i<3; i++)
			{
				delay(60000);
			}
			BUZ=1;						/*蜂鸣器灭*/
			EIE2  |= 0x40;              /*使能UART1中断*/
			EA=1;
		}
		_nop_();
	}
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// This routine initializes the system clock to use an 22.1184MHz crystal
// as its clock source.
//
void SYSCLK_Init (void)
{
   int i;                              /*延时计数器*/

   OSCXCN = 0x67;                      /*开始外部22.1184MHz晶体*/

   for (i=0; i < 256; i++) ;           /*等待外部晶体起振稳定*/

   while (!(OSCXCN & 0x80)) ;          /*查询标志位*/

   OSCICN = 0x88;                      /*用外部晶体频率作为系统时钟，并使能时钟丢失检测*/
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Configure the Crossbar and GPIO ports
//
void PORT_Init (void)
{
   XBR2    |= 0x44;                    /*使能UART1和交叉开关，弱上拉*/
   P0MDOUT |= 0x01;                    /*使能TX1推挽输出*/
   P1MDOUT |= 0x40;                    /*使能LED作为推挽输出*/
   P3MDOUT |= 0xdf;
}

//-----------------------------------------------------------------------------
// UART1_Init
//-----------------------------------------------------------------------------
//
// Configure UART1 using Timer1, for <baudrate> and 8-N-1.
//
void UART1_Init (void)
{
   SCON1  = 0x50;                      /*SCON1:模式1, 8-bitUART,使能RX*/
   TMOD   = 0x20;                      /*TMOD: 定时器1,定时器2, 8位重载*/
   TH1    = -(SYSCLK/BAUDRATE/16);     /*设置定时器1作为波特率的重载值*/
   TR1    = 1;                         /*开定时器1*/
   CKCON |= 0x10;                      /*定时器1用系统时钟作为时基*/
   PCON  |= 0x10;                      /*SMOD1 = 1*/
   //EIE2  |= 0x40;                    /*使能UART1中断*/
}

//-----------------------------------------------------------------------------
// Interrupt Handlers
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// UART1_ISR
//-----------------------------------------------------------------------------
void UART1_ISR (void) interrupt 20 using 3
{
	if((SCON1 & 0x01)==0x01)
	{
		SCON1 &= ~0x01;					/*请接收标志位*/
		temp = SBUF1;					/*保存接收数据*/
		ReceiveBit=1;					/*置接收位*/
	}
	SCON1 &= ~0x02;						/*清发送标志位*/
}