Civil Engineering Reference
In-Depth Information
Fig. 2.48
Partial networking—ECUs can be aimed deactivated and aimed woken up
are able to operate every time, are connected directly to the battery (Clamp 30).
However, ECUs, which are only able to operate after the start of the engine, are
connected to the battery voltage via the ignition key signal (Clamp 15). With this
method, the network is split into only two parts. Further parts can be realized by,
e.g. relays circuits. The disconnection of the supply lines leads to an additional ef-
fort of cabling or to a rigorous splitting in Clamp 15 and Clamp 30 ECUs which
does not meet the requirements of a dynamic wake-up behaviour.
2.5.2.2
Variant 2: Separate Wake Line
Through the integration of a wake line, ECUs can be woken up as well. It must be
distinguished between two different ways of signalling on the wake-up line. In case
of a signalling with voltage levels indicating between sleeping and awake, the same
disadvantages (global wake-up, not selective) of the above-described variant 1 are
given. The case of a pulse sequence indicating which ECU connected to the wake
line shall be woken up brings the advantage of a selective wake-up method but im-
plies high implementation costs. A simple protocol must be implemented to control
the wake conditions of a complex protocol.
2.5.2.3
Variant 3: Bus Levels
Additional cabling effort, lack of flexibility and high implementation costs of the
above-described variants lead to the conception that a solution is needed inside the
existing system. Considering the open system interconnection (OSI) layer 1, the
physical layer, special interpreted bus levels which are not affecting the already
