vcan_status_tag
===============

Here is the definition::

  typedef enum
    { VCAN_LINK           = 0, 
      VCAN_UNLINK         = 1, 
      VCAN_START_PER_XFER = 2, 
      VCAN_STOP_PER_XFER  = 3,
      VCAN_OBJECT_MODE    = 4,
      VCAN_OBJECT_SIGNAL  = 5, 
      VCAN_INIT           = 6, 
      VCAN_RESET          = 7, 
      VCAN_READ_OBJ_DATA  = 8,
      VCAN_READ_OBJ_CTRL  = 9,
      VCAN_READ_PBUFFER   =10,
      VCAN_GET_OBJECT_MODE=11
    } vcan_status_tag;

This is the type of the tag-field for the status driver-function.  Since the
status-driver function calls driver-sub-functions, the information which
sub-function to call is passed in a tag-field of this type. A field of this
type is only defined in the ``vcan_status_data`` - structure.

VCAN_LINK
  This sub-function links two objects on the two ports of a VME-CAN2 card.
  By this, the card acts like a router between two separate CAN networks.
  Note that only ports that belong to a single VME-CAN2 card can be linked.
  Note too, that on the first port you have to define a read object and on
  the second port you have to define a write object.

VCAN_UNLINK
  This function removes the link between two objects on two ports. See also
  ``VCAN_LINK``.

VCAN_START_PER_XFER
  With this sub-function, a periodic transfer on a certain CAN object is
  started, data from the object is written periodically to the CAN bus.

VCAN_STOP_PER_XFER
  This sub-function stops the periodic transfer on a certain CAN object. See
  also ``VCAN_START_PER_XFER``.

VCAN_OBJECT_MODE
  With this sub-function, the mode (read or write, remote or not remote) is
  defined for a CAN object.

VCAN_OBJECT_SIGNAL
  With this sub-function, a signal-object is defined.

VCAN_INIT
  Initializes all CAN-Id's of a port.

VCAN_RESET
  Resets the VME-CAN2 card.

VCAN_READ_OBJ_DATA
  read (dump) the card's data-area of an object

VCAN_READ_OBJ_CTRL
  read (dump) the card's control-area of an object

VCAN_READ_PBUFFER
  read (dump) the card's parameter buffer.

VCAN_GET_OBJECT_MODE
  read the mode of an object. This does also show whether the user-program
  is the owner of the object since it returns a VCAN_NOT_OWNER_ERR`` if
  applied to objects that are not owned by the current thread. This function
  basically returns the data (except for the net-number and the CAN-Id) that
  was used with the ``VCAN_OBJECT_MODE`` function to define the object.