UART_IIR_FIFO_ENABLED_16750
status1 = serial_in(up, UART_IIR) & UART_IIR_FIFO_ENABLED_16750;
status2 = serial_in(up, UART_IIR) & UART_IIR_FIFO_ENABLED_16750;
status2 == UART_IIR_FIFO_ENABLED_16750) {
status1 = serial_in(up, UART_IIR) & UART_IIR_FIFO_ENABLED_16750;
if (status1 == UART_IIR_FIFO_ENABLED_16750)