Freescale Semiconductor M68HC08 series, Руководство по проектированию

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Introduction
LIN-bus
DRM047 — Rev 0 Designer Reference Manual
MOTOROLA Introduction 15
The low beam of today’s headlamps is characterized by a specific shape
and distribution regulated by ECE regulations. Independent of the
speed, the type of road, and the weather conditions, the headlamps of
today are always constant. But we will have next generations Advanced
Front Lighting (AFS) systems soon. A new lighting system can be
adopted to this various conditions. The target is to achieve better
visibility at night, when directing the lights according to the steering
wheel angle or due to the speed. To see where the car is going, rather
than putting the light always straight, is the background of this idea. So
we have horizontal beam control. Other systems use an auxiliary
bending lamp. See
Section 9. References : 3 , 4 , 5 , 6 , 7 , and 8 .
Advanced headlamp systems are quite complex. They need
sophisticated optics, sensors and actuators. So, today the system costs
targets their implementation to high-end car segments. If we lower the
cost, we spread them to all car segments. A key factor in lowering the
system cost is integration and the use of reasonable components and
protocols.
This reference design describes a good solution for headlamp levelling
systems based on stepper motor actuators with a possibility of vertical
and also horizontal beam control. The system can benefit from a single
chip solution and communication via low-cost LIN-bus protocol.
1.4 LIN-bus
All modern car electronic communication is based on serial bus
protocols. These have many advantages over classical wired systems.
For example, a control system with stepper motor actuators can be split
into distributed controllers connected with a single-wire bus. There is no
doubt that this bus system saves on wiring and connectors, so the
system cost is significantly reduced.
The LIN-bus serial communication protocol (see Section 9.
References , 2 ) was designed for automotive applications, but it can also
be used for other devices (white-goods, printers, and copiers, for
example). In the case of car-body electronics, it is used for
air-conditioning, mirror control, seat control, and light levelling. The
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