9-3 FWD (9440) L4-2.0L Turbo (B207R) (2009)
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Information Bus: Description and Operation
Control Modules, General Description
Control Modules, General Description
The task of a control module is to control some type of function, such as fuel quantity, ignition time point or interior lighting. The control module
governs its outputs based on its program and the values from the sensor and bus.
CPU (Central Processing Unit)
The control module microprocessor (CPU) is the unit in the control module that does the work. The CPU performs a calculation each time the internal
clock ticks. Which calculation is to be done is determined by the program stored in ROM (Read Only Memory).
A CPU with 8, 16 or 32 bits is used in cars. In a 16-bit computer, 2 bytes are handled simultaneously with each clock pulse.
The CPU of a control module in the car is normally activated when the ignition is switched ON. The control module can also be activated through
actuation of a button on a panel, a door being opened or the remote receiver getting a radio signal. Control modules connected to the I-bus can be
activated by a voltage pulse. This pulse is close to B+ and is sent by the control module that is doing the "waking", after which it sends its message.
