Device and Method for Transmitting Data Between Two Physical Interfaces

Abstract

The invention is a device and a method for transmitting data between two physical interfaces which in motion in relation to one another along a trajectory. The device has a data transmission unit disposed between the physical interfaces, and a local oscillator is assigned to the physical interfaces to inject a local system time prevailing at the location of one of the physical interfaces. The local oscillator has at least one of the physical interfaces for receiving and generating at least one clock signal which is transmitted to the data transmitter and the local oscillator at least at the other physical interface which has a receiver for the at least one clock signal transmittable via the data transmission unit and a synchronizer of the local system times based on the received clock signal; and a buffer memory located at the physical interface which receives the data transmitted by the data transmitter to be temporarily stored.

Claims

1.-16. (canceled)

17. A device for transmitting digital data, comprising: physical interfaces comprising a first interface attached to a rotating device and a second physical interface attached to a stationary device; an annular data transmitter, disposed between the physical interfaces which transmits the digital data on a data transmission channel; a local oscillator, assigned to the physical interfaces, for injecting a local system time at a location of one of the physical interfaces, wherein the local oscillator includes at least at one of the physical interfaces for generating at least one clock signal and which transmits the at least one clock signal to the annular data transmitter and the local oscillator located at the other physical interface includes a receiver for receiving the at least one clock signal which is transmitted by the data transmitter on the data transmission channel, and a synchronizer for synchronizing the local system times based on the received at least one clock signal; and a buffer memory, located at the physical interface, for temporarily storing the digital data transmitted by the data transmitter.

18. The device as claimed in claim 17, wherein; the physical interfaces are identical.

19. The device as claimed in claim 17, wherein; the buffer memory has a memory capacity which is chosen depending on a temporal phase shift occurring in the digital data transmitted during the data transmission between the first device rotating relative to the stationary second device.

20. The device as claimed in claim 19, comprising: means for detecting the phase shift occurring during data transmission and means for defining the memory capacity depending on the phase shift during the data transmission.

21. The device as claimed in claim 17, wherein: the buffer memory is a ring memory.

22. The device as claimed in claim 17, wherein: the physical interfaces transmit and forward data bits.

23. The device as claimed in claim 17, wherein: the data transmitter transmits digital data contactlessly.

24. The device as claimed in claim 23, wherein: the data transmitter that transmits data contactlessly is one of a capacitive, inductive, acoustic, electromagnetic or optical coupling device.

25. The device as claimed in claim 17, wherein: the physical interface is one of an electrical, electromagnetic, acoustic or optical interface via which the digital data are transmittable with a standardized communication protocol.

26. The device as claimed in claim 17, wherein the physical interfaces are connected to a coupling element which is connected to one of the oscillators.

27. The device as claimed in claim 17, comprising; a converter for converting a parallel data stream into a serial data stream to enable the data transmission unit and the physical interfaces to transmit the digital data in a serial data sequence via the data transmitter.

28. A method for transmitting digital data via a data transmission channel between two physical interfaces each having a local system time with a first physical interface being fitted to a rotating unit and a second physical interface being fitted to a stationary unit, comprising: Generating and receiving a clock signal by one of the two physical interfaces; transmitting the clock signal occurs via the data transmission channel; receiving the clock signal by another of the two physical interfaces; synchronizing the local system times occurs at both physical interfaces; transmitting the digital data occurs via the data transmission channel; temporarily storing of the transmitted digital data occurred at one of the physical interfaces receiving the digital data; and reading the digital data from a memory and providing the digital data at the other physical interface.

29. The method as claimed in claim 28, comprising; temporarily storing the digital data in a cyclical manner with a ring memory.

30. The method as claimed in claim 28, wherein: transmitting the data contactlessly.

31. The method as claimed in claim 28, wherein: temporarily storing the transmitted digital data in a memory having storage capacity chosen according to a maximum temporal phase shift occurring in digital data transmitted during the data transmission between the first rotating device relative to the second stationary device.

32. The method as claimed in claim 28, wherein; Obtaining the clock signal with the digital data at one of the two physical interfaces.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0023] The device according to the invention and the method on which the device is based are explained in detail with reference to the drawings described below.

[0024] The invention is described below by way of example on the basis of example embodiments with reference to the drawings without restricting the general inventive concept. In the drawings:

[0025] FIG. 1 shows a block diagram for data transmission in real time,

[0026] FIG. 2 shows a block diagram for data transmission via a data transmission unit according to the prior art, and

[0027] FIG. 3a-b show eye diagrams.

DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1 shows a block diagram which represents a device according to the invention for transmitting data between two physical interfaces 1, 2 which are in each case are of identical design. A contactless data transmission unit 3 is disposed along the transmission channel connecting the two physical interfaces 1, 2. The data transmission unit 3 is designed, for example, in the form of a capacitively or inductively operating electrical data transmission unit which is disclosed, for example, in DE 44 129 58 A1. In one example embodiment described, there for transmitting data between two coupling units 31, 32 mounted rotatably in relation to one another, one coupling unit 31 provides an annular-shaped conductor structure which is disposed separated by a gap S from the other coupling unit 32 which provides stationary electrical electrode arrangement. Alternative design forms for configuring the data transmission unit 3 are obviously also conceivable, for example in the form of a contactless optical or electromagnetic or acoustic data transmission unit 3 or in the form of a contact-based data transmission unit 3 designed in the form a loop.

[0029] Oscillators 41, 42 are disposed in each case at each of the physical interfaces 1, 2 in order to be able to perform the data transmission between both physical interfaces 1, 2 in an error-free manner. Both oscillators 41, 42 need to be synchronized in order to perform the data transmission with only a short delay time and with high bus loads, such as if possible using the entire transmission capacity of the transmission channel. The time synchronization of both oscillators is performed according to the invention using at least one generated clock signal, for example at the location of the oscillator unit 41. The clock signal is transmitted via the same transmission channel via by which the payload is also transmitted from one physical interface to the other.

[0030] In the case of the example embodiment illustrated in FIG. 1, it is assumed that both physical interfaces 1, 2 are designed as parallel interfaces. In order to obtain a conversion of the parallel data format into a serial data format suitable for transmitting the data via the data transmission unit 3, a serializer/deserializer, SerDes, is disposed in each case between the physical interface 1, 2 and the data transmission unit 3 via which the at least one clock signal is also transmitted for the purposes of the time synchronization of the local system times on both oscillator units 41, 42.

[0031] The phase shift which randomly develops during the data transmission of the digital payload signals and which changes, particularly in the case of a rotating data transmission unit 3, is equalized for its compensation using a buffer memory 5 disposed at the receiving end. To do this, the payload is temporarily stored in a cyclical manner in the buffer memory 5 which is preferably designed in the form of a ring memory before being forwarded via the local clock to the physical interface 2 at the receiving end.

[0032] In the case of a unidirectional data transmission, for example from the physical interface 1 to the physical interface 2, the oscillator 41 serves as a master oscillator and the oscillator 42 disposed at the receiving end serves as a slave oscillator. A corresponding synchronizer for time synchronization is disposed on the slave oscillator 42 for synchronization purposes. Similarly, the buffer memory 5 is also disposed at the receiving end.

[0033] In the case of a bidirectional data transmission, at least one buffer memory 5 is to be provided on both sides of the data transmission unit 3. See also the buffer memory 5 on the side of the physical interface 1 indicated by a broken line in FIG. 1. In the case of a bidirectional data transmission, both oscillator units 41, 42 are not necessarily, but are advantageously also are designed for the generation and reception of clock signals. Conversely, if the clock signal is also made available on the customer side along with the data to be transmitted, the generation of a clock signal by the oscillator is not required. In this case of the external feed of the clock signal separately or jointly with the data to be transmitted, the externally fed clock signal can be used for the synchronization of the local system times in each case at the first and second interface.

[0034] With the device according to the invention, data could be transmitted error-free under real-time conditions via a rotatable data transmission unit 3. Cycle times of 1.12 s could be implemented which are far below the cycle time of 250 s or the minimum of 31.25 s required by the Profinet CC-C application. The empirically proven jitter of 25 ns is furthermore far below the maximum jitter of <1 s specified by the Profinet CC-C application. The device according to the invention therefore has a largely unrestricted compatibility with existing network structures.

REFERENCE NUMBER LIST

[0035] 1, 2 Physical interface [0036] 3 Data transmitter [0037] 31, 32 Coupling device [0038] 41, 42 Oscillator [0039] 5, 5 Buffer memory [0040] Transmission channel [0041] A Eye aperture [0042] SerDes Serializer/Deserializer