2808 FIFO receiving problem

hello,

problem's coming when a byte receiving thru 2808 FIFO block. Sometimes a byte is missing.  But in case of normal SCI mode (no FIFO mode), it never happened !!

my code is hereunder, it just waits a byte from RXD pin and returns received byte.

 unsigned char getch()
 { 
        while (!(SCIFFRXA&0x1f00));
        return(SCIRXBUFA);
 }

has something wrong?

original(no fifo function) code was,

 unsigned char getch()
 {
      while (!(0x40&SCIRXSTA));
      return (SCIRXBUFA);
 }

pls let me know.. what's the problem??