Daimler Chrysler Ag

Temic Telefunken Microelectronic Gmbh

Manfred Ammler

Guenter Anton Fendt

Peter Hora

Christian Lehrach

Norbert Mueller

The invention relates to a circuit layout for a serial transmission and reception interface, in particular for a vehicle occupant protection system, as well as a procedure for controlling the same. Existing central units, in particular vehicle occupant protection systems, featured in most cases separate serial transmission and reception interfaces for the various modules to be connected, causing costs to increase whenever an additional diagnosis module is to be connected. By means of a switchable circuit layout for the interface, this will be connected either to a communication module or to the diagnosis module. The circuit layout is particularly simple and space-saving, being set up by means of diode switches, and preferably features a potential tapping point for automatic switchover into diagnosis mode.

Circuit layout for a serial transmission and reception interface in

In a method and system for transmitting digital data, a data acceptance clock signal generator that has a controllable clock frequency in a peripheral module is correspondingly adapted to clock frequency information derived from a synchronization pulse train transmitted by a central unit. The same oscillator is used as a frequency source for determining the clock frequency information and for generating the data acceptance clock pulse. In this manner, simple RC oscillators are adequate to fulfill any requirements of long time accuracy of the oscillator. The clock frequency can be changed in that the central unit simply transmits altered clock frequency information. It is also possible to carry out an adjustment or adaptation in the case of deviations of the oscillator frequency in the peripheral unit. Preferably, the clock frequency information is derived from the reciprocal value of the time duration of at least one synchronization pulse, which is determined in a quantized manner by a first counter in a clock frequency information acquisition circuit which counts the number of oscillator pulses occurring during the synchronization pulse. The resulting count value is provided to a data acceptance clock signal generator, which is clocked by the same oscillator and counts the number of oscillator pulses until reaching a prescribed threshold value, whereupon it outputs a corresponding clock signal. By properly adapting numerical elements, it is also possible to process pulse width modulated signals using the present method and apparatus.

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Bergheim, Germany

Manfred Ammler