unsigned char gSendChar = FALSE;
unsigned char gNextChar = 0U;

#pragma interrupt=UART_TX_ISR
__interrupt void uart_tx_isr(void)
{
  if(gSendChar)
  UART_TX_REG = gNextChar;
  gSendChar = FALSE;
}

void uart_write(unsigned char c)
{
  if(!gSendChar)
  {
  gSendChar = TRUE;
  gNextChar = c;
  }
}

有道理，谢谢！