Serial Ports

        COM 1  COM 2
        3F8h   2F8h    TX-buffer               DLAB=0 (WRITE)
                       RX-buffer               DLAB=0 (READ)
                       Divisor latch LSB       DLAB=1

        3F9h   2F9h    Divisor latch MSB       DLAB=1
                       Interupt enable register

        3FAh   2FAh    Interupt identification registers

        3FBh   2FBh    Line control register

        3FCh   2FCh    Modem control register

        3FDh   2FDh    Line status register

        3FEh   2FEh    Modem status register