Pulse or digital communications – Synchronizers – Self-synchronizing signal
Reexamination Certificate
1999-03-29
2001-06-19
Tse, Young T. (Department: 2734)
Pulse or digital communications
Synchronizers
Self-synchronizing signal
C375S282000, C375S333000
Reexamination Certificate
active
06249558
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 198 13 965.9, filed in the German Patent Office on Mar. 28, 1998. The entire disclosure of the German application is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a method for transmitting digital data impulses between a transmitter and a receiver. The receiver includes a data acquisition signal generator (DASG) which is controllable in an open-loop manner for synchronizing the DASG with the data transmission.
BACKGROUND INFORMATION
European Patent Publication EP 0,813,321 A2 which claims the priority of two German Patent Publications DE 196 23 750 and DE 196 43 205, discloses a method for transmitting digital data impulses having two logic levels “0” and “1”. The just mentioned publication teaches the provision of a data acquisition frequency with the help of a high frequency oscillator clock signal, whereby the high frequency clock signal is ascertained from an impulse duration. According to the known method it is possible to cause a data acquisition signal generator (DASG), the acquisition frequency of which is controllable in an open loop manner, to track the transmission frequency of a transmitted signal or to equalize any frequency tolerance fluctuations by means of simple RC-oscillators. On the one hand, the high frequency clock signals, simply referred to as clock signals or clock frequency are used for acquiring a time duration of an impulse from which the acquisition frequency is derived. On the other hand, the clock signals are also serving as a stepping frequency for advancing counters which generate, upon reaching of threshold values, the system and data acquisition frequency. The threshold values on their part may also be derived from the clock signals, for example as portions of the time duration of one impulse.
However, a permanent follow-up or intermediate synchronization is not possible with a conventional bit sequence of digital data impulses having unknown impulse levels. Thereby, it is conventionally necessary to repeatedly perform a new synchronization after a known number of data impulses, by using new synchronization impulses.
The disclosure of EP 0,813,321 also discloses a further development for pulse width modulated signals, whereby each data impulse is provided with its pulse flank change which in turn makes possible a follow-up synchronization through the data impulses. A transformation of digital data impulses into a pulse width modulation, however, is rather subject to a substantial effort and expense and is thus not feasible for all applications.
Moreover, encoding methods for digital data impulses are known in the art which involve encoding that permits clock signal recovery. Especially the Manchester encoding method involves recoverable clock signals. Manchester encoding combines timing or synchronizing signals with data signals.
European Patent Publication EP 0,178,622 A2 discloses a method for the clock signal recovery in connection with a Manchester encoded data transmission with a voltage controlled oscillator (VCO) including a frequency divider, selector means and a phase detector. European Patent Publication EP 0,185,556 A2 and European Patent Publication 0,425,302 A2 disclose methods for the clock signal recovery for Manchester encoded signals or for a digital closed loop phase decoder (Phasenregelschleifendecoder).
The Manchester encoding method is very advantageous due to its ability to recover clock signals. However, Manchester encoding cannot be employed in certain prior art methods that transmit digital data impulses to a data acquisition signal generator (DASG). In the Manchester encoding method the impulse flank change takes place within a data impulse width between an inverted impulse half and a non-inverted impulse half. A flank change may not take place at the beginning or end of an impulse width if Manchester encoding is to be applied. For the above mentioned conventional method it is necessary that the impulse flank change takes place at the beginning or at the end of a data impulse width for ascertaining the clock frequency from the time duration of an impulse width. Hence, in the above described conventional methods it is not possible to use Manchester encoding.
OBJECTS OF THE INVENTION
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to cause a follow-up or intermediate synchronization of the data acquisition signal generator, whereby such follow-up synchronization is derived from synchronization impulses or a sync frequency or from data impulses or a data frequency by simple steps;
to avoid the need for using the time duration between the beginning and end of a single synchronization or data impulse as the base for deriving a clock frequency and/or an acquisition frequency;
to perform the synchronization centrally within a synchronization or data impulse where the impulse flank change takes place, so that a time duration between two impulse flank changes for counting stepping pulses from a stepping oscillator may extend over two consecutive impulses;
to use the point of time where an impulse flank change takes place as a synchronization point of time;
to use the time duration between two synchronization points of time for ascertaining a clock frequency or acquisition frequency even if these points of time are positioned in the center of two consecutive impulses;
to derive a current clock frequency or acquisition frequency by counting oscillator generated stepping pulses falling within the duration between two impulse flank changes, whereby the stepping pulse frequency is higher than the clock frequency and the acquisition frequency; and
to provide a digital data transmission method which is especially suitable for use in digital signal bus systems as part of passenger protection devices in passenger vehicles.
SUMMARY OF THE INVENTION
The method of the invention combines the following steps for transmitting digital data impulses having two logic levels “0” or “1” from a transmitter (T) to a receiver (R), wherein the receiver includes a data acquisition signal generator (DASG) having a controllable data acquisition frequency.
(a) Manchester encoding said data impulses so that each data impulse has a not inverted impulse half and an inverted impulse half with an impulse flank change between the two data impulse halves,
(b) providing and Manchester encoding synchronization impulses so that each synchronization impulse has a not inverted impulse half and an inverted impulse half with an impulse flank change between the two synchronization impulse halves,
(c) sending, prior to any data impulse transmission, at least one Manchester encoded synchronization impulse for synchronizing said data acquisition signal generator with respect to time and with respect to a sync frequency provided by said at least one synchronization impulse, which remains current for at least one data impulse next to be transmitted,
(d) defining by each impulse flank change a synchronization time point, whereby a time duration determined by two sequential synchronization time points represents a current impulse frequency,
(e) generating a stepping frequency to provide counter stepping pulses SP, so that said stepping frequency is larger than said current impulse frequency,
(f) performing said synchronizing of said data acquisition signal generator by stepping a counter with said stepping pulses during said time duration to provide a count of stepping pulses,
(g) deriving from said count of stepping pulses a current accepted sync frequency (T
akt
),
(h) deriving from said current accepted sync frequency a current data acquisition frequency for controlling said data acquisition signal generator,
(i) scanning said logic levels of said data impulses in response to said current data acquisition frequency and said synchronization time points, and
(j) performing a follow-up or intermediate synchronization of said data acquisition signal generator
Bauer Joachim
Bischoff Michael
Fendt Guenter
Karl Otto
Nitschke Werner
Fasse W. F.
Fasse W. G.
Temic Telefunken microeletronic GmbH
Tse Young T.
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