放个代码出来请砖家指点下
#include<stdio.h>
#include<sys/io.h>
#include<unistd.h>
#define BASE 0x378
#define wr(data) (data & 0xcf)
#define rd(data) (data | 0x20)
#define b1off(data) (data & 0xfe)
#define b1on(data) (data | 0x01)
unsigned char read_8049(int addr)
{
int data, j, a, b, max;
unsigned char tmp, code;
unsigned char buff[40];
/* we read a byte 40 times. why? because there are errors. the error
rate is as high as 15% when I tested. Inserting delays can lower
the error rate, but won't eliminate it. I removed artificial
delays after implementing "the redundant read and vote" thing.
*/
for (j=0; j<40; j++)
{
tmp = wr(inb(BASE+2)); // Write
tmp = b1off(tmp); // RESET off
outb(tmp, BASE+2);
outb((unsigned char)addr, BASE); // ADDR
// blink reset
outb(b1on(inb(BASE+2)), BASE+2);
outb(b1off(inb(BASE+2)), BASE+2);
tmp = rd(inb(BASE+2)); // Read
outb(tmp, BASE+2);
buff[j] = inb(BASE+4);
}
/* find the most frequent one among 40 reads */
max=0;
for (j=0; j<40; j++)
{
tmp = buff[j];
a = 0;
for (b=j; b<40; b++)
{
if(buff[b]==tmp) a++;
}
if(a > max)
{
code = tmp;
max = a;
}
}
return code;
}
int main()
{
int i;
/* initialize */
if (iopl(3)) return 1;
for(i=0; i <= 0xff; i++)
printf("%c", read_8049(i));
}
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