Civil Engineering Reference
In-Depth Information
Fig. 1.6
CAN error counting
1.2.4.4
Overload Handling
Another means of exception handling is the so-called
Overload Frame
. The struc-
ture of an
Overload Frame
is exactly the same as that of an Error Frame. The only
difference is that an
Error Frame
overwrites and destroys normal messages while
the
Overload Frame
is exclusively started in the
IFS
(see Fig.
1.7
).
There are two conditions for sending an
Overload Frame
. First, an
Overload
Frame
is sent when a
dominant
bit is seen in the first two bits of the
IFS
. Here,
the
Overload Frame
is used to synchronize all CAN nodes. On the other hand, a
CAN controller may use an
Overload Frame
to notify all other CAN nodes that it is
overloaded (not able to handle a new message immediately), caused by (IC) internal
delay times. The other CAN nodes will see the first
dominant
bit of the
Overload
