def attn(card, mode=None, files=None, seconds=None, payload=None, start=None):
    """Configure interrupt detection between a host and Notecard.

    Args:
        card (Notecard): The current Notecard object.
        mode (string): The attn mode to set.
        files (array): A collection of notefiles to watch.
        seconds (int): A timeout to use when arming attn mode.
        payload (int): When using sleep mode, a payload of data from the host
            that the Notecard should hold in memory until retrieved by
            the host.
        start (bool): When using sleep mode and the host has reawakened,
            request the Notecard to return the stored payload.

    Returns:
        string: The result of the Notecard request.
    """
    req = {"req": "card.attn"}
    if mode:
        req["mode"] = mode
    if files:
        req["files"] = files
    if seconds:
        req["seconds"] = seconds
    if payload:
        req["payload"] = payload
    if start:
        req["start"] = start
    return card.Transaction(req)