16550做串口通信，遇到麻烦了

curious_cat
curious cat
等级:
可用分等级：短工
总技术分：79
总技术分排名：102450

发表于：2008-08-23 00:34:145楼得分:75

读LSR寄存器，如果bit 0等于1，表示FIFO中有数据，需要一直读到LSR的bit0为0；
我做过串口卡，这样处理是没错的，可能是你的芯片设置有问题，初始化时需要使能接受FIFO.
下面例子供参考(基于PC的，PC里面的SUPER IO芯片里面有两个16550兼容UART).

/* Name : Sample Comm's Program - 1024 Byte Buffer - buff1024.c */
/* Written By : Craig Peacock <cpeacock@senet.com.au> */
/* Copyright 1997 CRAIG PEACOCK <cpeacock@senet.com.au> */
/* See http://www.senet.com.au/~cpeacock/serial.htm */
/* For More Information */
#include <dos.h>
#include <stdio.h>
#include <conio.h>
#define PORT1 0x2F8 /* Port Address Goes Here */
/* Defines Serial Ports Base Address */
/* COM1 0x3F8 */
/* COM2 0x2F8 */
/* COM3 0x3E8 */
/* COM4 0x2E8 */
#define INTVECT 0x0B /* Com Port's IRQ here */
/* (Must also change PIC setting) */
int bufferin = 0;
int bufferout = 0;
char ch;
char buffer[1025];
void interrupt (*oldport1isr)();
void interrupt PORT1INT() /* Interrupt Service Routine (ISR) for PORT1 */
{
int c;
do
{
c = inportb(PORT1 + 5);
if (c & 1)
{
buffer[bufferin] = inportb(PORT1);

bufferin++;
if (bufferin == 1024) bufferin = 0;
}
}while (c & 1);
outportb(0x20,0x20);
}

void dumpSioReg(int baseAddr)
{
int i;
printf("\nDump SIO register\n");
for(i = 0; i < 8; i++)
{
printf("baseAddr + %d: 0x%x\n", i, inportb(baseAddr + i));
}
}
void main(void)
{
int c;

outportb(PORT1 + 1 , 0); /* Turn off interrupts - Port1 */
oldport1isr = getvect(INTVECT); /* Save old Interrupt Vector for */
/* later recovery */
setvect(INTVECT, PORT1INT); /* Set Interrupt Vector Entry */
/* COM1 - 0x0C */
/* COM2 - 0x0B */
/* COM3 - 0x0C */
/* COM4 - 0x0B */
/* 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 = 56,700 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 */
outportb(0x21,(inportb(0x21) & 0xF7)); /* Set Programmable Interrupt */
/* Controller */
/* COM1 (IRQ4) - 0xEF */
/* COM2 (IRQ3) - 0xF7 */
/* COM3 (IRQ4) - 0xEF */
/* COM4 (IRQ3) - 0xF7 */
outportb(PORT1 + 1 , 0x01); /* Interrupt when data received */

dumpSioReg(PORT1); /*dump address*/
printf("\nSample Comm's Program. Press ESC to quit \n");
do
{
if (bufferin != bufferout)
{
ch = buffer[bufferout];
bufferout++;
if (bufferout == 1024) bufferout = 0;
printf("%c",ch);
}

if (kbhit())
{
c = getch();
outportb(PORT1, c);
}
} while (c !=27);
outportb(PORT1 + 1 , 0); /* Turn off interrupts - Port1 */
outportb(0x21,(inportb(0x21) | 0x08)); /* MASK IRQ using PIC */
/* COM1 (IRQ4) - 0x10 */
/* COM2 (IRQ3) - 0x08 */
/* COM3 (IRQ4) - 0x10 */
/* COM4 (IRQ3) - 0x08 */
setvect(INTVECT, oldport1isr); /* Restore old interrupt vector */
}

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