Reference time distribution over a network

• US 20010024455A1
• Filed: 02/16/2001
• Published: 09/27/2001
• Est. Priority Date: 02/18/2000
• Status: Active Grant

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Smsc Holdings Sarl
• Inventors: Roth, Eric, Heidelberger, Christoph, Dickmann, Georg, Thaler, Thomas
• Granted Patent: US 8,014,423 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock
• CPC Class Codes: H04L 12/40052 High-speed IEEE 1394 serial bus bus transfer protocol on a daisy chain bus using an embedded synchronisation G06F13/426
• CPC Class Codes: H04L 12/40091 Bus bridging LAN interconnection over a bridge based backbone H04L12/462; single bridge functionality H04L12/462
• CPC Class Codes: H04L 12/40097 Interconnection with other networks LAN interconnection over a bridge based backbone H04L12/462; single bridge functionality H04L12/462
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge

Abstract

A reference time distribution system and method use a data transmission network having a plurality of nodes to distribute the House Sync signal. A network-wide time signal is generated using a reference time generator, and the network-wide time signal is then distributed over the network to the plurality of nodes. At each node, the network-wide time signal is converted to a local synchronization signal for use in performing synchronization of the timing of each node. Either network-inherent timing and/or additional time signaling is used to provide the nodes attached to this network with a network-wide notion of time. The time information is converted locally into synchronization signals or time information as required by a respective application. When data is transported over the network, delay compensation is performed to simultaneously output different data streams that have been synchronously input into the network, regardless of the data path.

Claims

1. A method for distributing a reference time in a network having a plurality of nodes, the method comprising the steps of:

generating a network-wide time signal using a reference time generator;

distributing the network-wide time signal over the network to the plurality of nodes;

converting, at each respective node, the network-wide time signal to a local synchronization signal; and

synchronizing the timing of each node using the local synchronization signal.

2. The method of

claim 1

, further comprising the step of:

tracking signal propagation delay at each node of the network using the network-wide time signal; and

wherein the step of converting includes the step of;

generating the local synchronization signal using the signal propagation delay of the respective node.

3. The method of

claim 2

, wherein the step of tracking further comprises the steps of:

maintaining a network-wide time signal as a network cycle master signal at a designated cycle master node of the plurality of nodes of the network;

maintaining a local cycle master signal at each respective node of the network; and

determining the signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal.

4. The method of

claim 3

, wherein the network cycle master signal and each local cycle master signal is stored in a respective network cycle master register and local cycle master register, respectively, at each respective node.

5. The method of

claim 1

, wherein the network-wide time signal is a house synchronization (synch) signal.

6. The method of

claim 1

, wherein the local synchronization signal has an associated frequency.

7. The method of

claim 1

, wherein the step of synchronizing includes the step of:

phase locking the local synchronization signal to a predetermined cycle value.

8. The method of

claim 1

, wherein the step of synchronizing includes the step of:

performing delay compensation at each respective node.

9. The method of

claim 8

, wherein the delay compensation is performed by adding an extra signal delay to the local synchronization signal.

10. The method of

claim 1

, wherein the plurality of nodes includes:

at least one IEEE 1394-compliant node.

11. The method of

claim 1

, wherein the step of generating the network-wide time signal includes the step of:

utilizing a rubidium reference signal generator.

12. The method of

claim 1

, wherein the step of generating the network-wide time signal includes the step of:

utilizing a global positioning system (GPS)-based reference signal generator.

13. A system comprising:

a network including a plurality of nodes; and

a reference time generator for generating a network-wide time signal;

wherein a designated node of the plurality of nodes is connected to the reference time generator, and distributes the network-wide time signal over the network to the plurality of nodes; and

wherein each node of the plurality of nodes of the network converts the network-wide time signal to a local synchronization signal, and synchronizes the timing of each node using the local synchronization signal.

14. The system of

claim 13

, wherein each node tracks signal propagation delay using the network-wide time signal, and converts the network-wide time signal by generating the local synchronization signal using the signal propagation delay of the respective node.

15. The system of

claim 14

, wherein the designated node maintains the network-wide time signal as a network cycle master signal;

and

wherein each respective node of the plurality of nodes maintains a local cycle master signal, and determines a respective signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal.

16. The system of

claim 15

, wherein designated node includes a network cycle master register for storing the network cycle master signal;

and

each node of the plurality of nodes of the network includes a respective local cycle master register for storing the local cycle master signal.

17. The system of

claim 13

, wherein the plurality of nodes includes:

at least one IEEE 1394-compliant node.

18. A system for facilitating timing functions in a network, the system comprising:

a plurality of nodes forming the network, with each node performing local timing control;

a reference time generator for generating the network-wide time signal; and

a plurality of applications operating using timing functions under local timing control, with each node of the plurality of nodes associated with at least one application;

wherein a designated node of the plurality of nodes is connected to the reference time generator, and distributes the network-wide time signal over the network to the plurality of nodes; and

wherein each node of the plurality of nodes of the network converts the network-wide time signal to a local synchronization signal, and synchronizes the timing of each node and the at least one application associated with the respective node using the local synchronization signal.

19. The system of

claim 18

, wherein the designated node maintains the network-wide time signal as a network cycle master signal in a network cycle master register;

and

wherein each node tracks signal propagation delay using the network-wide time signal, and converts the network-time signal by generating the local synchronization signal using the signal propagation delay of the respective node, to maintain a respective local cycle master signal in a respective local cycle master register, and to determine a respective signal propagation delay at each respective node from the difference between the respective local cycle master signal and the network cycle master signal.

20. The system of

claim 18

, wherein the plurality of nodes includes:

at least one IEEE 1394-compliant node.