典型的单片机串口程序，你读得懂吗，有问题？

只看该作者 · 2010-11-25 17:36

/*** Initialization of Serial Port(Ex.Baud Rate setting) ***/
void InitSerial(void)
{SCON = 0x50; // SERIAL MODE 1, SM00 = 0, SM01 =1, REN=1
TMOD |= 0x20; // Timer1 MODE 2
PCON |= 0x80; // SMOD0 = 1
TL1 = 0xFC;  // Baud Rate Setting to 115200bps
TH1 = 0xFC;  // Baud Rate Setting to 115200bps
TR1 = 1;  // Timer1 START
txbufrflag = 1;
RI = 0;
TI = 0;
txdptro = 0;
txdptri = 0;
rxdptro = 0;
rxdptri = 0;
ES = 1;  //  1}

void PU_INT4(void) interrupt 4 //中断
{  EA = 0;
   if (RI)
      {  RI = 0;
      uartrxd[rxdptri++] = SBUF; }
   if (TI)
   { TI = 0;
      if (txdptro == txdptri)
         txbufrflag = 1;
      else
         SBUF = uarttxd[txdptro++];
   }
   EA = 1;
}

char putchar(char  accum)  // 串行口输出
{  while (((txdptri+1) & 0x0f) == txdptro);
uarttxd[txdptri++]=accum;
if (txbufrflag)
   {txbufrflag = 0;
   TI = 1;}
return accum;}

unsigned char GetcomLn(unsigned char *temp)
{unsigned char byData,count;
  count = 0;
while(rxdptro != rxdptri)
  {temp[count++]  = uartrxd[rxdptro++];
for(byData = 0; byData < 30; byData++)
   {if (rxdptri == rxdptro)  wait_1us(5);
      else  break;}
}
temp[count] = 0;  //字符串最后加一空格
return count;
}

请教问题：putchar(char accum)中 while (((txdptri+1) & 0x0f) == txdptro);有什么作用？
   以及GetcomLn中那个for循环有什么用？