UARTn_STATE
u8 status = mps2_uart_read8(port, UARTn_STATE);
while (mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_RX_FULL) {
while (mps2_uart_read8(port, UARTn_STATE) & UARTn_STATE_TX_FULL)
while (readb(port->membase + UARTn_STATE) & UARTn_STATE_TX_FULL)