INT 14h,  04h    Initialize driver

      Entry:  DX         port number

            ( BX         4F50h

              ES:CX         ^C flag address --- optional )

      Exit:   AX         1954h if successful

              BL         maximum function number supported
                         (not counting functions 7Eh and above)

              BH         rev of FOSSIL doc supported

    This is used to tell the driver to begin  operations,  and to check that
    the driver is installed. This function should be called before any other
    communications calls are made.  At this point all interrupts involved in
    supporting the comm port (specified in DX) should be set up for handling
    by  the  FOSSIL, then  enabled.  If BX contains 4F50h,  then the address
    specified in ES:CX is that of a ☼lag byte in the application program,
    to be incremented when  ↕s detected in the keyboard service routines.
    This is an optional service and only need be supported on machines where
    the keyboard service can't (or won't) perform an INT 1Bh or INT 23h when
    a Control-C is entered.  DTR is raised by this call.  The baud rate must
    NOT be changed by this call.

    NOTE: Should an additional call to this service occur  (2 Inits or Init,
    Read,Init, etc.) the driver should reset all buffers, flow control, etc.
    to the INIT state and return SUCCESS.