The Network

The network

General
Increasing demands for further functionality in the car, both by statutory requirement and customers, have led to an increased complexity in the car.
This, in turn, has encouraged developments towards more flexible electrical systems. The CAN network is a result of this research (CAN = Controller Area Network). The network permits the transmission and receipt of a large number of different commands and messages on the same wires. Every command or message used to require a separate wire. Using networks has allowed functionality to be expanded without increasing the number of wires.
The number of commands and messages that can be handled by the network depends on the speed of the network and the length of the message / command. The Volvo network which is based on a Controller Area Network (CAN), can transmit over 500 different signals and approximately 100 messages (also known as frames). Each message can contain several signals, for example a message to the rear electronic module (REM) can contain all the signals for how the tail lamps should be lit.

Advantages of a network

Easier to add further functions and install accessories.
Because the control modules in the network are already connected to each other and are easy to add more information to, all that is required is:
- to connect the sensors to the nearest control module
- to connect the controlled component to the nearest control module
- to download software to alter the configuration and programming of the network.
The length of the wiring and the number of components which are introduced with the car are less than previously.
An example of this is the addition of cruise control for the car.
Before the introduction of the network the installation of control modules, switches, vacuum pumps, vacuum servos, hoses and cable harnesses was necessary.
With the network only the installation of a switch and the downloading of software which alters the configuration of the car is required.

Easier to introduce logical functions.
Logical functions can be described as "if this happens, the following must take place". For example, the system is programmed so that if a tail lamp breaks, a message is transmitted via the CAN network to the driver information module (DIM) so as to warn the driver.
The only thing you need to do to introduce a logical function is alter the programming of control modules affected - the rear electronic module (REM) and the driver information module (DIM) in the example above.
Introduction of logic functions does not increase the number of components or cables.

Easy to adapt the system to customer and market requirements.
The functions can be altered depending on the requirements/demands of the customer and market. An example of this could be fog tail lamps. Certain markets use two fog tail lamps, others only use one on the driver's side. Previously it was required that different replacement parts were stored for different markets. Now the same replacement part can be used for all markets, by changing the programming depending on the market.

A similar basic system can be used for a whole model programme.
Similar networks (hardware) can be used for a large number of different cars.
The only thing which differentiates the cars is:
- the components (control modules, sensors controlled components etc.) which are connected to the system
- Which components do what
- Which components/functions are standard /optional/accessories
- The configuration /programming of the system.