深入浅出VC++串口编程之DOS的串口编程

发布时间：2006-02-20 10:42:19　来源：天极开发网友评论 0 条

　　3.硬件查询

　　通过读取和写入串口UART对应的硬件端口，我们可以控制串口的收发。请看下面的例子：

/* Name : Sample Comm's Program - Polled Version - termpoll.c */
/* Written By : Craig Peacock <cpeacock@senet.com.au> */
#include <dos.h>
#include <stdio.h>
#include <conio.h>

００００００００００００００００００００#define PORT1 0x3F8

/* Defines Serial Ports Base Address */
/* COM1 0x3F8 */
/* COM2 0x2F8 */
/* COM3 0x3E8 */
/* COM4 0x2E8 */

void main(void)
{
　int c;
　int ch;
　outportb(PORT1 + 1, 0); /* Turn off interrupts - Port1 */

　/* PORT 1 - Communication Settings */

　outportb(PORT1 + 3, 0x80); /* SET DLAB ON */
　outportb(PORT1 + 0, 0x03); /* Set Baud rate - Divisor Latch Low Byte */
　/* Default 0x03 = 38,400 BPS */
　/* 0x01 = 115,200 BPS */
　/* 0x02 = 57,600 BPS */
　/* 0x06 = 19,200 BPS */
　/* 0x0C = 9,600 BPS */
　/* 0x18 = 4,800 BPS */
　/* 0x30 = 2,400 BPS */
　outportb(PORT1 + 1, 0x00); /* Set Baud rate - Divisor Latch High Byte */
　outportb(PORT1 + 3, 0x03); /* 8 Bits, No Parity, 1 Stop Bit */
　outportb(PORT1 + 2, 0xC7); /* FIFO Control Register */
　outportb(PORT1 + 4, 0x0B); /* Turn on DTR, RTS, and OUT2 */

　printf("/nSample Comm's Program. Press ESC to quit /n");

　do
　{
　　c = inportb(PORT1 + 5); /* Check to see if char has been */
　　/* received. */
　　if (c &1)
　　{
　　　ch = inportb(PORT1); /* If so, then get Char */
　　　printf("%c", ch);
　　} /* Print Char to Screen */

　　if (kbhit())
　　{
　　　ch = getch(); /* If key pressed, get Char */
　　　outportb(PORT1, ch);
　　} /* Send Char to Serial Port */
　}
　while (ch != 27); /* Quit when ESC (ASC 27) is pressed */
}

　　程序中的

c = inportb(PORT1 + 5); /* Check to see if char has been */
/* received. */
if (c &1)

　　检查PORT1 + 5端口地址，通过c&1可以判断是否有数据被UART接收到。关于UART对应的端口范围，从图2中也可以直观地看出。

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