//*------------------------------------------------------*/
//*    Cexp8s.cpp(查詢方式半雙工串行通信接口實驗-發送端程序)*/
//*    查詢方式半雙工串行通信發送程序 Source File          */
//*    Copyright (c) 2001 by HUST                        */
//*------------------------------------------------------*/
#include <conio.h>     //kbhit();
#include <stdio.h>     //printf();
#include <dos.h>       //delay();

#define data51 0x318    //8251A數據口
#define ctrl51 0x319	   //8251A命令/狀態口
#define ctrl55 0x313    //8255命令口
#define timer2 0x316    //8253的2號計數器端口
#define timctl 0x317    //8253命令口
//#define clk    1193182 
#define factor 16	   //波特率因子16

unsigned long int clk = 1193182;//8251輸入時鐘頻率（十六進制表示）
//定時常數數組
int tc_table[8]={
	110,	// 0=110bps
	150,    // 1=150b/s
	300,    // 2=300b/s
	600,    // 3=600b/s
	1200,     // 4=1200b/s
	2400,     // 5=2400b/s
	4800,     // 6=4800b/s
	9600      // 1=9600b/s
};

void int51();           //初始化8251a
void set_bps(int bps);		   //8253-5記數初值計算與裝入

void main()
{
	int getvalue=0;
	int temp=-1;
	int sletter,rletter,status;
	for(;;)
	{
		clrscr();
		printf("\n 0---110\n 1---150\n 2---300\n 3---600\n 4---1200\n 5---2400\n 6---4800\n 7---9600\n");
     printf("\n please take one of Baud-rates\n");
		getvalue=getch();
		if((getvalue<'0') || (getvalue>'7'))
		{
			printf("\n Input error! try again please! \n");	//error message
			getch();
			continue;
		}
		else
		{
			break;
		}
	}
	temp = getvalue - '0';
	set_bps(tc_table[temp]);
	int51();
	printf("\n now enter the serial communication");
	printf("\n end with 'Esc'\n");
	outportb(ctrl55,0x80);//置PC6=1，打開8253-5的GATE2，開始輸出方波
	outportb(ctrl55,0x0d);
	for(;;)//判斷是否Esc鍵
	{
		if (kbhit()){//若無鍵按下，則轉接收
			if((sletter=getche())==0x1b)//是ESC？是，則退出，并返回DOS
			{
				outport(ctrl55,0x0c);//關閉8253
				return;
			}
			else{
				status=inportb(ctrl51);//獲取8253 TXRDY 狀態
				if((status&0x01)!=0)//已準備好，則將鍵入的字符發送出去
				{
					outportb(data51,sletter);
				}
			}
		}
		else{
			status=inportb(ctrl51);//已準備好，即有數據傳送過來，則接收1個字符
			if((status&0x02)!=0)
			{
				rletter=inportb(data51);
				printf("\n%c",rletter);
			}
		}
	}

}

void int51()
{
	outportb(ctrl51,0x00);
	delay(100);
	outportb(ctrl51,0x40);//8251復位
	delay(100);
	outportb(ctrl51,0x4a);//8251A方式命令
	delay(100);
	outportb(ctrl51,0x27);//8251A工作命令
}

void set_bps(int bps)
{
	int i,sendhigh,sendlow;
	i=clk/bps;
	i=i/factor;//計算計數初值
	sendhigh = (i>>8)&0x00ff;
	sendlow  = i & 0x00ff;
	outportb(timctl,0xb6);
	outportb(timer2,sendlow);//裝計數初值低字節
	outportb(timer2,sendhigh);//裝計數初值高字節
}