如何将这个buffer清0

1万 · 2014-1-11 08:56

89S51外扩一个8255的
我设置了8个buffer,8255的PA口每扫描一次，这8个buffer就会有一组数值。然后再扫描。。。当我扫描完一次以后，如何将这个buffer清0

1万 · 2014-1-11 08:57

还有就是我想将每次buffer的值储存起来，当我扫描完N次以后，可以看到这些值。

1万 · 2014-1-11 08:58

做一个FIFO队列。
typedef struct scan_queue_s ｛
   unsigned char read; //  read position
   unsigned char write;//  write positon
   unsigned char num;// buffer size
   unsigned char buffer[8];
｝queue_t;
//put value into queue
unsigned char write_queue(queue_t * queue, unsigned char value)
{
      if(queue->num == 8)//buffer full,return 1;
            return 1;
      queue->buffer[queue->write++] = value;
      queue->num++;
      if(queue->write == 8)
               queue->write =0;
      return 0;
}
//get value from queue
unsigned char read_queue(queue_t *queue, unsigned char *value)
{
      if(queue->num == 0)//buffer is empty,return 1;
            return 1;
      *value = queue->buffer[queue->read--];
      queue->num--;
      return 0;
}