Civil Engineering Reference
In-Depth Information
Figure 3.10
Example: CAN gateway for automotive
CPU load will be generated. A message received on bus A will be copied to bus B
and depending on the settings, the transmission request can be set automatically;
the amount of data bytes can be reduced and/or the identifier can be changed au-
tomatically. This feature is quite useful also in combination with the GW feature.
The FIFO/GW combination allows to reroute messages automatically between two
buses running at different speeds, without overwriting message objects, or to buffer
their contents via software.
Figure
3.10
shows an example of the speed; information can be automatically
forwarded from the Powertrain module to the door module, to lock the door at
speeds greater than 30 km/h automatically.
In the following example, a message block of four messages having the same
identifier shall be routed to a bus running at a lower baud rate.
3.4.2.4
FIFO/GW Combination
To route the messages from bus A to bus B (Fig.
3.11
) in an optimal way, a message
object assigned to bus A has to be configured a source GW object and to point to a
four-state FIFO, assigned to bus B. This combination allows rerouting the messages
automatically and it does not cost any CPU performance after initialization. The
received messages are copied to the FIFO and the message will be sent according to
CAN prioritization rules. Software activities are only needed, in case the data bytes
are changed. No software interaction is needed, in case the data length core or the
identifier is changed. Be aware that in case the data length code is increased, the
new data byte will include a 0 × 0, if not changed by software.
