Patent Application
20130182783
This application claims the priority of European Patent Application EP11165972.8 filed 13. May 2011, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.
The present invention relates to a method for serial transmission of data between at least one sender and at least one receiver.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Serial data transmission methods are known in the art. Frequently, however, the necessity arises as well as sending the transmitted data, which will also be referred to as payload data below by way of distinction, to be able to send additional data. Such additional data is referred to in technical terminology as sideband data, by way of distinguishing it from other data. Sideband data can be used for diagnostic purposes, to encode a communication link quality, etc.
Two approaches have previously been considered for the transmission of sideband data. On the one hand, separate interfaces or interfaces with additional lines are used. However in a disadvantageous manner this increases the costs of the communication link between two or more communication users. On the other hand, consideration has also been given to packing the sideband data into telegrams transferred during data transmission between two communication users and normally only containing payload data or appending it to such telegrams. However the definition of the payload data telegrams must be modified or expanded for this purpose. In addition the transmission of sideband data in payload data telegrams requires the transfer of payload data telegrams to be functioning. This can however be a significant disadvantage in the transmission of diagnostic information in the sideband data for example. In addition appending sideband data to a payload data telegram reduces the amount of payload data able to be transmitted in a unit of time.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method for the transmission of sideband data.
According to one aspect of the present invention, a method for serial transmission of data in form of telegrams and symbols between at least one sender and at least one receiver, includes the steps of converting on the sender side an item of data into a symbol, converting on the receiver side the symbol into an item of data, identifying a telegram with special symbols, transmitting at least one first and one second pause symbol different from the special symbols for encoding a pause between telegrams, and deriving information from a sequence of the pause symbols.
According to another aspect of the invention, an automation device in a communication system connecting at least two automation devices via a serial link, includes means for converting on a sender side of the at least two automation devices an item of data into a symbol, means for converting on the receiver side of the at least two automation devices the symbol into an item of data, means for identifying a telegram with special symbols, means for transmitting at least one first and one second pause symbol different from the special symbols for encoding a pause between telegrams, and means for deriving information from a sequence of the pause symbols.
The received sideband data is the derived information or refers back to the derived information. The sideband data on the sender side to be transferred are encoded by pause symbols. To this end, a definition of the symbols provided for serial data transmission is expanded. In transmission, telegram or send pauses—referred to overall as a pause or transmission pause—modern serial data transmission protocols send a pause symbol provided to identify such pauses and for synchronizing the communication users, which is also referred to in specialist terminology as an idle symbol. The approach proposed here makes provision for a first and a second pause symbol to be used instead of the previous individual pause symbols. With respect of the identification of the transmission, pause and/or for synchronization all pause symbols, i.e. at least the first and second pause symbol, are evaluated by the serial data transmission protocol like the previous individual pause symbol. For transmission, sideband data are encoded as a sequence of pause symbols. The pause symbols or also a transition between pause symbols are thus now given information content.
Advantageously, symbols which are typically sent in the transmission pauses in modern serial data transmission protocols are used to transfer the sideband data, so that, with the approach proposed here, the transmission of the sideband data is possible without loss of bandwidth. In addition the sideband data can be transmitted without physical modification of the interface, such as additional lines or the like, so that the approach proposed here can be used at low cost and can easily be used for existing communication systems.
In respect of the derivation of information from a sequence of pause symbols, each pause symbol may be assigned a status value, i.e. for two pause symbols for example “0” or “1”, “high” or “low”, and the information is produced from the sequence of the resulting status values.
According to another advantageous feature of the present invention, a status value may be assigned to a transition between a pause symbol and another pause symbol, especially a transition between the first and the second pause symbol and the second and the first pause symbol, i.e. “0” or “1 “,” high” or “low” for example, and the information is again produced from the sequence of the resulting status values. If a transition is also detected from one pause symbol to a next identical pause symbol, four possible transitions are produced, with two pause symbols to which a separate status value can be assigned in each case, i.e. “00”, “01”, “10” and “11” for example.
Advantageously, instead of two pause symbols, more than two pause symbols may be used, with four pause symbols a consideration is for example to assign the first second third and fourth pause symbols then produces the following status values in binary notation: “00”, “01”, “10” and “11”. When the status value is encoded by the transition between two pause symbols, 16 possible transitions are already produced for four pause symbols and thereby sixteen different status values. If only transitions between different pause symbols are to encode a permitted status value, twelve different status values are still produced for four pause symbols.
According to another advantageous feature of the present invention, the symbol may be converted into an item of data by a so-called 4B/5B encoding. 4B/5B encoding is a largely direct-current-free encoding. In addition, it is also ensured that sufficient flank changes are present in the signal in order to make clock recovery possible. Alternatively, for converting a symbol into a data item, a so-called 8B/10B encoding or generally any encoding operating with symbols may be used, wherein 8B/10B encoding, as well as the properties of 4B/5B encoding, also has the property of being direct current-free. 8B/10B is widespread and is used for example in USB2.0, USB3.0, Firewire800; PCIe 1.x and 2.x, DVI, etc. further encoding processes operating with symbols and thus to be considered are especially 64b/66b (10 Gbit-Ethernet), 128b/130b (PCIe 3.0) and Eight-to-Fourteen (Compact Disc).
According to another advantageous feature of the present invention, the method may be implemented in software or in software and firmware. The invention also relates to a computer program with program code instructions able to be executed by a computer for implementing the method and on the other hand a storage medium with such a computer program and finally also an automation device, in the memory of which or in the hardware provided therefor, e.g. in the form of an ASIC, as a means for executing the method and its embodiments, such a computer program is loaded or is able to be loaded. The method can also be implemented in hardware, e.g. in the form of an interface component expanded by a functionality in accordance with the method proposed here for a serial link. The invention is thus also such an interface component or an automation device with such an interface component. A controller, e.g. a programmable logic controller or a decentralized peripheral device, a sensor or an actuator, a drive control device, etc. are considered as an automation device. Accordingly, the term automation device should include all devices, components or systems, i.e. as well as for example controls such as programmable logic controls, process computers, (industry) computers and the like, also drive controllers, frequency converters and suchlike, as are used or can be used for open-loop, closed-loop control and/or monitoring of technological processes, e.g. for reshaping or transporting material, energy or information, etc., wherein energy is especially applied to or converted through suitable technical facilities such as sensors or actuators for example.
Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:
Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Turning now to the drawing, and in particular to
Additional automation devices 24, 26, 28 are linked to individual automation devices 14, 16, 18 via a serial link 22, wherein a field bus 20 can also be basically embodied as a serial link with serial data transmission. The serial link 22 shown should thus expressly only serve as an example of a possible serial link in an automation system 10. The additional automation devices, in the configuration shown in
During sending, a sender, namely one of the automation devices 14-18, creates a telegram frame with the special symbols 34 “J” and “K” to identify the beginning of the telegram and later the special symbols 34 “T” and “R” to identify the end of the telegram and in between, as payload data of the telegram 32 for each item of data 36 to be transmitted, the associated symbol 34 (payload data symbol). A receiver of such a telegram 32 recognizes the beginning and the end of the telegram 32 from the special symbols 34, namely “J” and “K” or “T” and “R”, and converts the symbols 34 (payload data symbols) included in the telegram 32 into an item of data 36 in each case. Transmitted in between two telegrams 32 are special symbols 36 encoding a pause (transmission pause) which are referred to below as pause symbols 38. The transmission of a number of pause symbols 38 in a send or receive pause is usual. In the Fast Ethernet Standard IEEE802.3, for example, a number of twenty-two pause symbols 38 between two telegrams 32 is defined. As with the symbols 34 and the respective associated item of data 36, in
To implement the method each device connected to a serial link 22 has an interface component 46, 48, or the functionality of such an interface component 46, 48 integrated into another functional unit, especially a semiconductor component. An example of such an interface component 46, 48 is the interface component known by the abbreviation UART. Such an interface component 46, 48 is a possible location for implementing the method, namely for transmission of data wherein, during the telegram pauses, at least one first and one second symbol 40, 42 encoding a pause is transmitted, and for deriving information from a sequence of such pause symbols 40, 42. The generation and transmission of the pause symbols 40, 42 in accordance with the information to be transferred as sideband data 44, e.g. diagnostic information, is undertaken in this case by the respective sender. The derivation of information from a sequence of such pause symbols 40, 42, i.e. an indirect or direct derivation of the respective sideband data 44, is undertaken by the respective receiver. For this purpose the respective interface component 46 of the sender receives input signals 50 in respect of the information to be transmitted as sideband data 44 and the respective interface component 48 of the receiver makes available the received sideband data 44 as output signals 52. Not shown in the figure in this case is that the respective interface component 46, 48 on the sender side also receives input signals in respect of the payload data to be transferred and on the receiver side on the basis of the received payload data generates output signals relating to said data.
An interface component 46, 48 as shown in
Individual aspects of the description given here can thus be summarized briefly as follows: A method is specified as serial transmission of data between the at least one sender and at least one receiver, wherein the data transmission is undertaken in the form of telegrams 32 and with symbols 34, by an item of data 36 being converted into a symbol 34 on the sender side and the symbol 34 being converted into an item of data 36 on the receiver side wherein, to identify a telegram 32, special symbols 34 are used and wherein, in telegram pauses, a symbol 38, 40, 42 encoding a pause is transmitted, wherein the method is characterized in particular by the fact that for transmission of data during the telegram pauses at least one first in one second symbol encoding a pause—first and second pause symbol 40, 42—is transmitted and that information is derived from a sequence of pause symbols 40, 42.
While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein:
| Number | Date | Country | Kind |
|---|---|---|---|
| EP11165972.8 | May 2011 | EP | regional |
