DATA NETWORK WITH A TIME SYNCHRONIZATION SYSTEM

• US 20090100189A1
• Filed: 10/02/2008
• Published: 04/16/2009
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Original Assignee: Harman Becker Automotive Systems GmbH (Samsung Electronics Co. Ltd.)
• Inventors: Bahren, Frank, Schopp, Harald
• Granted Patent: US 9,319,239 B2
• Time in Patent Office: Days
• US Class Current: 709/231
• CPC Class Codes: H04L 12/422 Synchronisation for ring networks Time Division Multiplex ring networks, e.g. SDH/SONET H04J3/085
• CPC Class Codes: H04L 12/423 with centralised control, e.g. polling
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion
• CPC Class Codes: H04L 12/437 Ring fault isolation or reconfiguration for SDH/SONET ring networks H04J3/085

Abstract

A system matches frame counter values between a timing master and one or more slave devices in a synchronous network. To detect synchronization losses, a timing master counts transmitted frames of a continuous data stream. When a synchronization loss occurs, the timing master transmits a message to the slave devices that includes a synchronization frame counter value. The message synchronizes the frame counter value of the timing master to the frame counter value of the slave devices.

Claims

1. A method for matching frame counter values of a timing master and at least one slave device in a synchronous network having a ring topology comprising:

counting a continuous data stream transmitted by a timing master through a frame counter in communication,

counting frames of the continuous data stream received from the timing master by the at least one slave device through a local frame counter in the ring topology,

transmitting a message comprising a synchronization frame counter value when the timing master detects a loss of synchronization or loss of a transmitted frame in the continuous data stream by the timing master, and

setting the frame counter value of the at the at least one slave device to the synchronization frame counter value received from the timing master.

2. The method of claim 1, where the synchronization frame counter value is processed to synchronize the frame counter value of the timing master and the frame counter value of the at least one slave device.

3. The method of claim 2, where the frame at which the loss of synchronization has been detected by the timing master, corresponds to the frame counter value n, and the synchronization frame counter value corresponds to the frame counter value n+1.

4. The method of claim 1, where the synchronization frame counter value corresponds to the number of frames that have been successfully transmitted by the timing master before a loss of synchronization is detected.

5. The method of claim 1, further comprising detecting whether a loss of synchronization in the continuous data stream has occurred by the timing master.

6. The method of claim 1, where detecting whether a loss of synchronization in the continuous data stream has occurred comprises determining when a preamble of a transmitted frame is not received by the timing master at an expected time of day.

7. The method of claim 1, further comprising detecting whether a loss of a transmitted frame in the continuous data stream has occurred.

8. The method of claim 1, where detecting whether a loss of a transmitted frame in the continuous data stream has occurred comprises determining a change in the number of slave devices during the operation of the synchronous network.

9. The method of claim 1, where the timing master transmits the message, comprising a local synchronization frame counter value, periodically in time.

10. The method of claim 1, where the timing master transmits the message comprising a local synchronization frame counter value with a timestamp of a timing master'"'"'s reference clock.

11. The method of claim 1, where the synchronization frame counter value or the synchronization frame counter value and a timestamp is comprised in a respective field of a control data section of a transmitted frame.

12. The method of claim 1, where frames are transmitted periodically in time by the timing master.

13. The method of claim 12, where the at least one slave device synchronizes with the timing master'"'"'s clock reference by determining a real-time clock reference based on the last received timestamp of the timing master'"'"'s clock reference and the number of frames that have been received since the reception of the timestamp of the timing master'"'"'s clock reference.

14. The method of claim 13, further comprising enabling an application programmable code retained in a storage media to be executed by the at least one slave device to access the determined real-time reference.

15. The method of claim 1, further comprising enabling an application program retained in a storage media to be executed by the at least one slave device to access the frame counter value of the slave device.

16. The method of claim 1, where a network controller of the slave device provides the frame counter.

17. The method of claim 1, where changes in the states of the at least one slave device or any events that occur at the at least one slave device are monitored and stored in a local memory with a respective frame counter value, and where the application executed by the at least one slave device is enabled to access the respective stored information on changes in the states of the at least one slave device or any events that occur at the at least one slave device together with the frame counter values.

18. The method of claim 1, where the synchronous network has a ring topology and comprises a Media Oriented Systems Transport (MOST) network implemented in an automotive environment.

19. A timing master in a synchronous network having a ring topology comprising:

a processor that maintains a frame counter adapted to count frames of a continuous data stream transmitted by a transmitter of a timing master, where the processor is further adapted to detect a loss of a synchronization or a loss of a transmitted frame in the continuous data stream, and where

the transmitter is further adapted to transmit a message comprising a synchronization frame counter value when the processor detects the loss of synchronization or the loss of a transmitted frame in the continuous data stream.

20. A slave device in a synchronous network comprising:

a processor that maintains a frame counter adapted to count frames of a continuous data stream received from a timing master;

where the processor is further adapted to set the frame counter value of at least one slave device to a synchronization frame counter value received from the timing master.

23. A computer-readable medium storing instructions that, when executed by a timing master, cause the timing master to initiate matching frame counter values of the timing master and at least one slave device, by

counting frames of a continuous data stream transmitted by a transmitter of the timing master,

detecting a loss of synchronization or a loss of a transmitted frame in the continuous data stream, and

transmitting a message comprising a synchronization frame counter value when a loss of synchronization or loss of a transmitted frame in the continuous data stream is detected.

24. A computer-readable medium storing instructions that, when executed by the at least one slave device, cause the at least one slave device to adapt its frame counter value, by

counting frames of the continuous data stream received from a timing master, and

setting the frame counter value of at least one slave device to a synchronization frame counter value received from the timing master.