Communication system and method for synchronizing a plurality of network nodes after a network lock condition occurs

• US 8,861,664 B2
• Filed: 06/15/2012
• Issued: 10/14/2014
• Est. Priority Date: 06/15/2012
• Status: Active Grant

• Current Assignee: Smsc Holdings Sarl (Microchip Technology Incorporated)
• Original Assignee: Smsc Holdings Sarl (Microchip Technology Incorporated)
• Inventors: Akkihal, Shivanand I., Mueller, Rainer
• Primary Examiner(s): NGUYEN, LEON VIET Q
• Application Number:
  US13/524,323
• Publication Number:
  US 20130336435A1
• Time in Patent Office: 851 Days
• Field of Search: 370/503, 375/356, 713/400
• US Class Current: 375/356
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0647 Synchronisation among TDM nodes
• CPC Class Codes: H04J 3/0673 using intermediate nodes, e.g. modification of a received timestamp before further transmission to the next packet node, e.g. including internal delay time or residence time into the packet

Abstract

A communication system and method is provided herein for synchronizing a plurality of network nodes after a network lock condition occurs within a network. According to one embodiment, the method may generate a local trigger signal simultaneously at each of the plurality of network nodes by compensating for unique phase delays attributed to each of the plurality of network nodes. As described herein, the local trigger signals may be used for synchronizing devices, such as multimedia devices, which may be coupled to the network nodes. More specifically, the local trigger signals may be used to synchronize events occurring within devices, which are coupled to different nodes of the network.

Claims

1. A method for synchronizing a plurality of network nodes after a network lock condition occurs within a network, the method comprising:

calculating a unique phase delay at each of the plurality of network nodes after the network lack condition occurs, wherein each unique phase delay consists of an amount of phase delay needed for a data frame to travel between a receive pin of a network node to a transmit pin of the same network node; and

generating a local trigger signal simultaneously at each of the plurality of network nodes by compensating for the unique phase delays calculated at each of the plurality of network nodes, and wherein the local trigger signals are used to synchronize events occurring at each of the plurality of network nodes.

2. The method as recited in claim 1, further comprising:

storing an accumulated phase delay within each of the plurality of network nodes, wherein the accumulated phase delay stored within each of the plurality of network nodes is computed by combining the unique phase delays attributed to the network nodes arranged between a source node of the network and each respective network node.

3. The method as recited in claim 2, wherein after the step of calculating the unique phase delays and before the step of storing an accumulated phase delay, the method further comprises:

transmitting the unique phase delays calculated at each of the plurality of network nodes to all network nodes; and

calculating the accumulated phase delay at each of the plurality of network nodes by combining the unique phase delays attributed to the network nodes arranged between the source node and each respective network node.

4. The method as recited in claim 2, wherein after the step of calculating the unique phase delays and before the step of storing an accumulated phase delay, the method further comprises transmitting the accumulated phase delay computed at each network node to a next downstream network node.

5. The method as recited in claim 2, further comprising:

measuring an offset value between a source trigger signal received by or generated within the source node and a predetermined byte of a data frame generated by a master node of the network; and

transmitting the offset value across the network to each of the plurality of network nodes.

6. The method as recited in claim 5, wherein after the step of measuring and before the step of transmitting, the method further comprises adding a jitter value calculated at the source node to the offset value and transmitting the combined jitter and offset values across the network to each of the plurality of network nodes.

7. The method as recited in claim 5, wherein the offset value is transmitted within the predetermined byte of the data frame to each of the plurality of network nodes.

8. The method as recited in claim 7, further comprising:

receiving data frames transmitted by the master node at each of the plurality of network nodes;

wherein if a particular network node detects the offset value within the predetermined byte of one of the received data frames, the method as performed by the particular network node further comprises;

initiating a countdown timer from a predetermined value;

generating a local trigger signal once a count value of the countdown timer is equivalent to the predetermined value minus a combined delay of the offset value and the accumulated phase delay stored within the particular network node; and

synchronizing an event at the particular network node to the local trigger signal.

9. The method as recited in claim 8, wherein prior to the step of transmitting the offset value the method comprises transmitting an indication of a valid trigger across the network to each of the plurality of network nodes, and wherein prior to the step of detecting the offset value the method comprises detecting the indication of the valid trigger.

10. The method as recited in claim 1, wherein the method enables the events occurring at each of the plurality of network nodes to be synchronized to a common time marker.

11. The method as recited in claim 10, wherein the events comprise generation of clock signals at each of the plurality of network nodes.

12. The method as recited in claim 10, wherein the events comprise data sampling at each of the plurality of network nodes.

13. The method as recited in claim 10, wherein the events comprise generation of input/output (I/O) signals at each of the plurality of network nodes.

14. The method as recited in claim 13, wherein the I/O signals are used to synchronize display screens coupled to each of the plurality of network nodes.

15. The method as recited in claim 13, wherein the I/O signals are used to synchronize image capture by cameras coupled to each of the plurality of network nodes.

16. The method as recited in claim 13, wherein the I/O signals are used to synchronize audio signals supplied to speakers coupled to each of the plurality of network nodes.