//MAX485的使能轉(zhuǎn)換時會出很麻煩的問題！！！
//通信協(xié)議：主機發(fā)地址信息，相應(yīng)從機發(fā)地址應(yīng)答信息（地址+0x80）
//??????????主機發(fā)命令信息，相應(yīng)從機發(fā)命令應(yīng)答信息（命令+0x80）
//??????????命令a（主發(fā)從收命令），命令號：0x0a，主機首先發(fā)數(shù)據(jù)數(shù)量N，緊接著發(fā)N個數(shù)據(jù)，最后發(fā)2字節(jié)CRC校驗（高位在前）
//?????????????????????????????????從機無需應(yīng)答，只需把數(shù)據(jù)連同檢驗存入接收緩沖區(qū)即可，接著進行校驗，校驗正確發(fā)肯定應(yīng)答（0xaa）
//?????????????????????????????????否則發(fā)否定應(yīng)答（0xee），主機若收到否定應(yīng)答，則全部從發(fā)（從地址開始）
#include
#include

#define?uchar?unsigned?char
#define?uint??unsigned?int

uchar*??receive_buffer_head=0xa0;		??//接收數(shù)據(jù)緩沖區(qū)
uchar*??send_buffer_head=0x60;			??//發(fā)送數(shù)據(jù)緩沖區(qū)
uchar*??current_receive_pointer;??????????//當(dāng)前接收指針
uchar*??current_send_pointer;			??//當(dāng)前發(fā)送指針
uchar*??crc_head=0x80;
uchar?receive_buffer_length;??????????????//接收緩沖區(qū)數(shù)據(jù)長度
uchar?send_buffer_length;			??????//發(fā)送緩沖區(qū)數(shù)據(jù)長度
uchar?respon;?????????????????????????????//應(yīng)答信息
uchar?slave1adress=0x01;				??//從機1地址
uchar?slave2adress=0x02;				??//從機2地址
uchar?slave3adress=0x03;				??//從機3地址
uchar?crc_high;
uchar?crc_low;
uint??crc;
uchar?command_a=0x0a;

sbit?sending=P2^0;????????????????????????//發(fā)送指示燈??
sbit?receiveing=P2^1;?????????????????????//接收指示燈
sbit?test=P2^2;
sbit?send_enable=P2^7;????????????????????//發(fā)送使能，只有發(fā)送時為高，其余時間為低
sbit?receive_enable_inv=P2^6;?????????????//接收使能，低電平有效




//***********************************************************
//??????????????????????延時函數(shù)，延時x毫秒
//***********************************************************
void?DelayMS（uint?ms）	????????		???
{
???uchar?i;
???while（ms--）
???for（i=0;i<120;i++）;
}



//***********************************************************
//?????????????????寫主機的發(fā)送緩沖區(qū)數(shù)據(jù)
//這里簡單地往發(fā)送緩沖區(qū)寫入a~z
//***********************************************************
void?Write_Send_Buffer（）
{??	
???uchar?i;
???uchar*?temp_pointer;
???temp_pointer=send_buffer_head;
???for（i=0x00;i<0x1a;i++）
???{
????*temp_pointer=i+0x41;
	?temp_pointer++;
???}??
}



//***********************************************************
//		?????????????RS-485初始化
//***********************************************************
void?RS485_initial（）
{
?????sending=0;?????????????????????//發(fā)送指示燈??
?????receiveing=0;??????????????????//接收指示燈
	?test=0;
?????current_receive_pointer=receive_buffer_head;????//初始化當(dāng)前的接收緩沖區(qū)指針指向接收緩沖區(qū)首地址
?????current_send_pointer=send_buffer_head;??????????//初始化當(dāng)前的發(fā)送緩沖區(qū)指針指向發(fā)送緩沖區(qū)首地址??????????????
	?receive_buffer_length=0;?????????//接收緩沖區(qū)數(shù)據(jù)長度初始化為0
?????send_buffer_length=0;			??//發(fā)送緩沖區(qū)數(shù)據(jù)長度初始化為0
	?send_enable=1;???????????????????//初始化發(fā)送有效
	?receive_enable_inv=1;????????????//接收無效
	?REN=0;???????????????????????????//初始化為不允許接收
	?P1=0x88;
			??

}


//***********************************************************
//UART初始化
//***********************************************************
void?UART_initial（）
{
???EA=1;????????????????????????//開總中斷
???ES=1;????????????????????????//開串行口中斷
???ET1=1;???????????????????????//開定時計數(shù)器1中斷
???SCON=0xd0;	????????????????//設(shè)置串行方式，1101?0000?方式3，不允許多機，允許接收
???TMOD=0x20;	????????????????//設(shè)置計數(shù)器方式，

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件????????477??2012-12-16?14:42??RS_485_多機通信\RS-485說明文檔.txt

?????文件?????126001??2012-12-16?14:27??RS_485_多機通信\rs485.DSN

?????文件??????12569??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485

?????文件???????8898??2012-12-16?14:29??RS_485_多機通信\主機host\again_rs485.c

?????文件???????3129??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.hex

?????文件?????????39??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.lnp

?????文件??????14396??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.LST

?????文件??????14472??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.M51

?????文件??????14185??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.OBJ

?????文件???????4203??2012-12-16?14:20??RS_485_多機通信\主機host\again_rs485.plg

?????文件??????55227??2012-12-16?14:30??RS_485_多機通信\主機host\again_rs485.uvopt

?????文件??????13245??2012-12-13?21:58??RS_485_多機通信\主機host\again_rs485.uvproj

?????文件??????55230??2012-12-16?14:29??RS_485_多機通信\主機host\again_rs485_uvopt.bak

?????文件??????13241??2012-12-13?20:54??RS_485_多機通信\主機host\again_rs485_uvproj.bak

?????文件??????12568??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1

?????文件??????12280??2012-12-16?14:29??RS_485_多機通信\從機1\again_rs485_slave1.c

?????文件???????3319??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.hex

?????文件?????????53??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.lnp

?????文件??????20101??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.LST

?????文件??????14986??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.M51

?????文件??????14070??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.OBJ

?????文件???????4332??2012-12-16?14:19??RS_485_多機通信\從機1\again_rs485_slave1.plg

?????文件??????55252??2012-12-16?14:30??RS_485_多機通信\從機1\again_rs485_slave1.uvopt

?????文件??????13266??2012-12-13?21:58??RS_485_多機通信\從機1\again_rs485_slave1.uvproj

?????文件??????55254??2012-12-16?14:29??RS_485_多機通信\從機1\again_rs485_slave1_uvopt.bak

?????文件??????????0??2012-12-13?20:54??RS_485_多機通信\從機1\again_rs485_slave1_uvproj.bak

?????文件??????11837??2012-12-16?14:19??RS_485_多機通信\從機2\again_rs485_slave2

?????文件??????11950??2012-12-16?14:19??RS_485_多機通信\從機2\again_rs485_slave2.c

?????文件???????3213??2012-12-16?14:19??RS_485_多機通信\從機2\again_rs485_slave2.hex

?????文件?????????53??2012-12-16?14:19??RS_485_多機通信\從機2\again_rs485_slave2.lnp

............此處省略15個文件信息