Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1996-02-02
2001-04-03
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S522000
Reexamination Certificate
active
06212198
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for the common transmission of digital source and control data between data sources and sinks being connected through data lines, in which source and control data are transmitted in a format prescribing a clocked sequence of individual bit groups of equal length.
The present invention shows a network with ring-like architecture, in which subscribers forming data sources and data sinks are connected through a single data line. Through that data line, the source and control data are transferred in a continuous data stream which is synchronous to a clock signal. The clock signal is generated by a single subscriber. All other subscribers synchronize themselves to the clock signal. Purely asynchronous data transmission methods have to be differentiated therefrom as packet or package-oriented data transmission methods, for example ATM-methods.
Such methods are used wherever different electrical and electronic devices that are intended to exchange information with one another are linked to one another through the use of data lines in what is sometimes a complicated way. In the audio field, for instance, communication between interlinked data sources on one hand, such as CD players, radio receivers and cassette tape recorders, and the data sinks connected with them on the other hand, such as amplifier-speaker combinations, can be controlled by such a method.
In the course of development of CD players, the so-called SPDIF format (Sony/Philips Digital Interface Format), which is also known by the designation IEC 958, has become established as the standard. That format prescribes transmission of the data in a frame that includes two subframes or bit groups. Each subframe includes a preamble of four bits for control data, followed by 24 bits for source data and ending with four bits for special control data. One subframe of each frame is assigned to the left audio channel, and the other subframe is assigned to the right audio channel.
Since the rigid structure of that format has proved to be disadvantageous for data transmission in complex communications systems, co-pending U.S. application Ser. No. 08/595,838 now U.S. Pat. No. 5,844,953) entitled “Method for Common Transmission of Digital Source and Control Data Between Data Sources and Data Sinks Connected through Data Lines” has been filed simultaneously with the instant application, in which a substantially more-flexible format for data transmission is described.
Fundamentally, all of those methods have in common the fact that both source and control data must be converted into a fixedly specified format prior to transmission. On one hand, that can be time-consuming and can cause unacceptable delays in time-critical applications. On the other hand, with a specified transmission format, only control data that are defined for transmission with that format, or in other words that are contained in the “instruction set” of the particular transmission format, which set includes the individual control data, can be transmitted. Moreover, the length of the data words that can be transmitted is restricted by the length of the individual bit groups.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for the common transmission of digital source and control data between data sources and data sinks connected through data lines, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and with which data of an arbitrary type and length can be transmitted quickly and flexibly from one device to another.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for the common transmission of digital source and control data between data sources and sinks being connected through data lines, which includes transmitting the source and control data in a format prescribing a clocked sequence of individual bit groups of equal length, which comprises reserving at least one bit position in each bit group for the transmission of unformatted data, allocating the unformatted data bitwise to the reserved bit positions of successive bit groups, and assigning the unformatted data to a certain data source/data sink as a function of the control data.
On one hand, data of arbitrary length can be transmitted through the use of the unformatted transmission of the data at reserved bit positions of successive bit groups. On the other hand, no conversion of the data to a structure adapted to the transmission format takes place, thus eliminating a time lag in transmission caused by conversion. Moreover, control data that are not contained in the transmission format “instruction set” which includes the individual control data can also be transmitted. These control data, which are unknown to the transmission format, are associated with one or more specific receiving devices as a function of the “regular” control data of the transmission format and are evaluated directly by these devices.
The method is not limited to the transmission of audio data. It can also be used to transmit arbitrary data, such as fax data, status data, telephone card data or other control data. For instance, besides the audio devices mentioned at the outset, video cameras, video-CD players, telephones, fax machines, microphones, CD-ROMs, or computer hard disks can be linked together. Furthermore, particularly in motor vehicles, control and monitoring units can also be included in the network. For example, it is possible to incorporate devices for monitoring the function of outside lights or tire pressure or of devices for measuring or controlling engine rpm or charge pressure of a turbocharger. In this way, if the tire pressure is dropping, for instance, the audio system can issue a warning in the form of a memorized text over the speaker.
In accordance with another mode of the invention, at the beginning of transmission of unformatted data each time, a starting identification code is transmitted as a control datum. Thus the start of the unformatted data is apparent to each receiver in a simple way.
In accordance with a further mode of the invention, at the beginning of transmission of unformatted data each time, the length of the unformatted data sequence is transmitted as a control datum. In this way, the end of the unformatted data can be determined for each receiver in a simple way.
In accordance with an added mode of the invention, at the end of transmission of unformatted data each time, an ending identification code can be transmitted as a control datum, so that in this way the end of the unformatted data is identified. If not only the starting identification code and the length but also an ending identification code are transmitted, then the redundant information can be used to detect transmission errors.
In accordance with an additional mode of the invention, each data sink is assigned a unique address, and at the beginning of the transmission of unformatted data each time, the address of the data sink for which the unformatted data are intended is transmitted as a control datum. The corresponding data sink can thus tell from the transmitted address that it is the receiver of the unformatted data, and begins with the readout of these data.
If the unformatted data are intended for various data sinks in common, then advantageously at the beginning of the transmission the addresses of these data sinks intended as receivers are transmitted as control data.
In accordance with yet another mode of the invention, and in particular in addition, each data source is assigned a unique address, and at the beginning of the transmission of unformatted data each time, the address of the data source which outputs the unformatted data is transmitted as a control datum.
If the data of a certain data source are always to be transmitted to the same data sinks, then these data sinks can tell from the transmitted address of the data source that they are intended as receivers of the unformatted d
Heck Patrick
Hetzel Herbert
Becker GmbH
Greenberg Laurence A.
Lee Chiho Andrew
Lerner Herbert L.
Nguyen Chau
LandOfFree
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