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CAN-Bus 1 (advantages/disadvantages)
| Read here a short introduction in digital signals. |
| Task |
- All control units dispose of all information of the sensors.
- No differences of information among the control units.
- Less wiring expenditure.
- Improved fault detection, emergency run and
diagnostics.
- Functional elements as for example indicator flashers or fuses
are replaceable.
- After short circuit abolition immediate return to normal
functioning.
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| Complete exchange of information among all control units |
In the good old days a car featured just one control unit, regulating the injection. Today there are vehicles with far more than 50 control units. If some of them are in need of the same information, one sensor should be
sufficient. In this case, the head control unit transmits the signal further via the Controller Area Network Bus (CAN-Bus). This reduces the amount of wire and allows a quicker error analysis which includes even the
plug-in connectors.Theoretically, one sufficiently large service wire would be enough for a whole car - besides of course the available ground - and a thin control wire which would not even have to be shielded. In
theory, because
- the data transfer capacity of the Bus is limited,
- different speeds make sense,
- the (data) safety is not equally important everywhere.
| Different speeds, high transmission safety |
Because only special chips with input and output unit, ROM and RAM (controller) can access the network, every actuator (e.g., the rear light unit) and every switch must have such a controller. The other possibility is a
direct connection to a control device in the Controller Area Network Bus. Because of the vastness of possible demands it is advisable to use CAN - Buses of different speeds. For example, slower Buses for the
comfort electronics, and faster ones for the engine electronics or safety electronics. There are even companies (e.g., Opel) which abolish the second data line for less relevant features all together. In addition, e.g., the
video-transmission technology clearly has higher requirements for the amounts of data to be transferred, for which the Controller Area Network Bus is not suitable. A possible alternative for this is the MOST-Bus. 05/07
| Advantage |
- More reliably, e.g., fewer plug-in connectors that might cause
errors.
- Wiring less complicated, more economic.
- Easy to implement, changes, too.
- Additional elements (e.g.,
control units) are easy to integrate.
- Installation place exchangeable without electric problems.
- Wire may be diagnosed.
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| Disadvantage |
- High software expenditure.
- Undesirable interaction more probable.
- Danger of incomplete technology for the customer.
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| History |
| 1983 | Start of the development |
| 1985 | Presentation by Bosch and Intel |
| 1987 | Completion of the interface |
| 1988 | Intel Chip ready for use |
| 1991 | First CAN-Buses (engine, transmission, dashboard) Mercedes S-class |
| 2001 | CAN-Buses for cars of the lower middle class |
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