Communications network and method of controlling the communication network

• US 20030067873A1
• Filed: 09/06/2002
• Published: 04/10/2003
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Future Link Systems, LLC (Vector Capital Corporation)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Zinke, Manfred, Fuhrmann, Peter
• Granted Patent: US 7,583,692 B2
• Time in Patent Office: Days
• US Class Current: 370/230
• CPC Class Codes: H04J 3/0652 Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] bus network with centralized control in which slots are of a TDMA packet structure H04L12/4035
• CPC Class Codes: H04J 3/0694 Synchronisation in a TDMA node, e.g. TTP
• CPC Class Codes: H04L 12/40013 Details regarding a bus controller
• CPC Class Codes: H04L 12/40026 Details regarding a bus guardian
• 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 12/44 Star or tree networks
• CPC Class Codes: H04L 5/1484 operating bytewise

Abstract

The invention relates to a communications network with at least two network nodes, between which data may be transmitted via a transmission medium,

in which a communications schedule is provided which allots time slots to the network nodes for access to the transmission medium,

in which the network nodes each comprise at least one communication controller with a first scheduler for controlling access by the network nodes to the transmission medium according to the communications schedule,

in which the communications network comprises at least one bus guardian with a second scheduler for monitoring accesses by the network nodes to the transmission medium according to a monitoring schedule,

in which the communication controller comprises means for generating a local, independent clock signal and a global clock signal, which may be influenced by at least one parameter of the communications system and

in which the global clock signal is provided both to control the first schedulers of the communication controllers and to control the second scheduler of the bus guardian.

Claims

1. A communications network with at least two network nodes, between which data may be transmitted via a transmission medium,

in which a communications schedule is provided which allots time slots to the network nodes for access to the transmission medium,

in which the network nodes each comprise at least one communication controller with a first scheduler for controlling access by the network nodes to the transmission medium according to the communications schedule,

in which the communications network comprises at least one bus guardian with a second scheduler for monitoring accesses by the network nodes to the transmission medium according to a monitoring schedule,

in which the communication controller comprises means for generating a local, independent clock signal and a global clock signal, which may be influenced by at least one parameter of the communications system and

in which the global clock signal is provided both to control the first schedulers of the communication controllers and to control the second scheduler of the bus guardian.

2. A communications network as claimed in claim 1, characterized in that the bus guardian comprises a first monitoring circuit, which monitors the global clock signal of the communication controller by means of the local clock signal of the communication controller.

3. A communications network as claimed in claim 1, characterized in that the bus guardian comprises a bus guardian oscillator, which supplies a local clock signal to a second monitoring circuit, and in that the second monitoring circuit monitors the local clock signal of the communication controller by means of the local clock signal of the bus guardian.

4. A communications network as claimed in claim 3, characterized in that the bus guardian oscillator is an RC oscillator.

5. A communications network as claimed in claim 3, characterized in that the bus guardian comprises a failure monitoring circuit, which monitors failure of the bus guardian oscillator and in that, in the event of failure of the bus guardian oscillator, the failure monitoring circuit causes blocking of access by the node associated with this bus guardian to the transmission medium or generates an error message.

6. A communications network as claimed in claim 1, characterized in that an algorithm is implemented in the communication controller of the network, by means of which algorithm the global clock signals of the communication controllers are adjusted to one another or in relation to a reference signal.

7. A communications network as claimed in claim 2, characterized in that the first monitoring circuit comprises a counter, which determines the number of periods of the local clock signal over one or more periods of the global clock signal and in that the first monitoring circuit causes blocking of access by the node associated with the bus guardian or by the nodes associated with the bus guardian to the transmission medium, if the number of counted periods lies outside a predeterminable tolerance zone.

8. A communications network as claimed in claim 3, characterized in that the second monitoring circuit comprises a counter, which determines the number of periods of the local clock signal of the communication controller over one or more periods of the local clock signal and in that the second monitoring circuit causes blocking of access by the node associated with the bus guardian or by the nodes associated with the bus guardian to the transmission medium, if the number of counted periods lies outside a predeterminable tolerance zone.

9. A communications network as claimed in claim 1, characterized in that the communication controllers comprise a quartz oscillator, in that the local clock signal of the communication controllers is derived by means of a fixed divider from the signal of the quartz oscillator and in that the global clock signal of the communication controllers is derived by means of a variable divider from the signal of the quartz oscillator, wherein the divider ratio of the variable divider may be influenced by at least one parameter of the communications system.

10. A communication controller for a communications network, in which the communication controller is provided with a first scheduler for controlling access by a network node to a transmission medium of the network according to a communications schedule,

in which the communication controller comprises means for generating a local, independent clock signal and a global clock signal, which may be influenced by at least one parameter of the communications network,

in which the global clock signal is provided both to control the first scheduler of the communication controller and to control a second scheduler of a bus guardian.

11. A bus guardian for a communications network for monitoring access by at least one network node to the transmission medium according to a monitoring schedule, in which the bus guardian comprises a first monitoring circuit, which is provided to monitor a global clock signal of the communication controller by means of a local clock signal of a communication controller.

12. A method of controlling a communications network with at least two network nodes, between which data may be transmitted via a transmission medium,

in which a communications schedule is provided which allots time slots to the network nodes for access to the transmission medium,

in which the network nodes each comprise at least one communication controller with a first scheduler for controlling access by the network nodes to the transmission medium according to the communications schedule,

in which the communications network comprises at least one bus guardian with a second scheduler for monitoring accesses by the network nodes to the transmission medium according to a monitoring schedule,

in which the communication controller generates a local, independent clock signal and a global clock signal, which may be influenced by at least one parameter of the communications system and

in which the global clock signal controls both the first schedulers of the communication controllers and the second scheduler of the bus guardian.