def hexa_word(data, separator = ' '):
        """
        Convert binary data to a string of hexadecimal WORDs.

        @type  data: str
        @param data: Binary data.

        @type  separator: str
        @param separator:
            Separator between the hexadecimal representation of each WORD.

        @rtype:  str
        @return: Hexadecimal representation.
        """
        if len(data) & 1 != 0:
            data += '\0'
        return separator.join( [ '%.4x' % struct.unpack('<H', data[i:i+2])[0] \
                                           for i in compat.xrange(0, len(data), 2) ] )