IN               Input Byte or Word                  Flags: not altered

IN accumulator,port

Logic:    accumulator   (port)

IN transfers a byte or a word from a port to AL or AX. The port may be
specified by an immediate byte value (for ports 0 through 255) or by
the DX register (allowing access to all ports).

                                                                          
Operands                  Clocks   Transfers  Bytes   Example
                        byte(word)
accumulator, immed8       10(14)       1        2     IN AL,45h
accumulator, DX           8(12)        1        1     IN AX,DX
                                                                          

Notes:         It is advised that hardware not use I/O ports F8h
through FFh, since these are reserved for
controlling the math coprocessor and future
processor extensions.

See also: OUT

IN Input Byte or Word