def convert_dec_to_hex_string(decimal_value):
    """
    This function converts a decimal value into 8-byte hex string
    and reverses the order of bytes.
    """
    hex_str = '{:016x}'.format(decimal_value)
    reversed_hex = []
    index = len(hex_str)
    while index > 0:
        reversed_hex += hex_str[index - 2:index].capitalize() + ' '
        index = index - 2
    return ''.join(reversed_hex)