NAME
    PRD_QUERY -- query printer port/line status

FUNCTION
    This command returns the status of the printer port's lines and
    registers.  Since the printer port uses either the serial or
    parallel port for i/o, the actual status returned is either the
    serial or parallel port's status.

IO REQUEST
    io_Message      mn_ReplyPort set if quick I/O is not possible
    io_Device       preset by the call to OpenDevice
    io_Command      PRD_QUERY
    io_Data         ptr to 2 UBYTES where result will be stored.

RESULTS
    io_Data       BIT  ACTIVE  FUNCTION (SERIAL DEVICE)

         LSB       0    low    reserved
                   1    low    reserved
                   2    low    reserved
                   3    low    Data Set Ready
                   4    low    Clear To Send
                   5    low    Carrier Detect
                   6    low    Ready To Send
                   7    low    Data Terminal Ready
         MSB       8    high   read buffer overflow
                   9    high   break sent (most recent output)
                  10    high   break received (as latest input)
                  11    high   transmit x-OFFed
                  12    high   receive x-OFFed
               13-15           reserved


    io_Data       BIT  ACTIVE  FUNCTION (PARALLEL DEVICE)

                   0     hi     printer busy (offline)
                   1     hi     paper out
                   2     hi     printer selected
                                  (WARNING: the bit 2 line is also
                                   connected to the serial port's ring
                                   indicator pin on the A500 and A2000)
                 3-7            reserved

    io_Actual     1-parallel, 2-serial