Method and apparatus for can bus auto-termination

• US 20070120574A1
• Filed: 11/29/2005
• Published: 05/31/2007
• Est. Priority Date: 11/29/2005
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Houston, Timothy, Garrafa, Carlos, Browder, Charles
• Granted Patent: US 7,312,628 B2
• Time in Patent Office: Days
• US Class Current: 326/30
• CPC Class Codes: H04L 25/0298 Arrangement for terminating transmission lines

Abstract

A cable area network (CAN) bus termination (100) is provided by an interface 104 operably coupling a cable detection input pin (3), a switch (120) and a termination resistance (130) to detect the presence and absence of one or more cables (108). The termination resistance (130) is automatically enabled to create terminations at end nodes and is automatically disabled to provide a daisy-chain connection between interim nodes of a multi-cable system.

Claims

1. A CAN bus termination circuit, comprising:

a cable detection input pin, a switch and a termination resistance operably coupled to detect the presence and absence of one or more cables and to automatically enable and disable the termination resistance to the one or more cables in response thereto.

2. The CAN bus termination circuit of claim 1, wherein the cable detection input pin provides a logic level to the switch to provide auto-termination upon cable contact to the node.

3. The CAN bus termination of claim 1, wherein the switch comprises a transistor circuit.

4. The CAN bus termination of claim 1, wherein the switch comprises a multiplexer.

5. The CAN bus termination of claim 1, wherein the switch comprises a logic gate.

6. The CAN bus termination of claim 1, wherein the switch comprises an electrical relay.

7. The CAN bus termination of claim 1, wherein the switch comprises an optical relay.

8. A cable area network (CAN) bus termination, comprising:

an interface for receiving at least one cable connector;

a circuit coupled to the interface; and

the circuit automatically providing a resistive termination by default in the absence of a cable connect or being coupled to the interface, and the circuit automatically providing a resistive termination in response to a single cable connector being coupled to the interface, and the circuit automatically providing a series connection between two connectors being coupled to the interface.

9. The CAN bus termination of claim 8, wherein the interface comprises a single interface for receiving a Y-split cable.

10. The CAN bus termination of claim 8, wherein the interface comprises first and second interface portions for receiving connectors of two straight cables.

11. The CAN bus termination of claim 8, wherein the circuit comprises an electrical circuit.

12. The CAN bus termination of claim 8, wherein the series connection is provided by disabling the resistive termination.

13. A cable area network (CAN) bus termination circuit, comprising:

first and second interfaces for receiving a least one cable connector;

a switch coupled to the first and second interfaces; and

a termination resistance being selectively controlled by the switch so as to couple to the first and second interfaces when one cable connector is attached to one of the first and second interfaces, and the termination resistance being disabled by the switch when two cable connectors are coupled to the first and second interfaces.

14. A communication system, comprising:

a plurality of cable area network (CAN) components;

a plurality of cables daisy-chaining the plurality of CAN components such that two end nodes are separated by a plurality of interim nodes, the plurality of cables being provided with terminations by an electrical switching circuit that automatically enables termination resistances to the two end nodes while disabling termination resistances to the interim nodes.

15. The communication system of claim 14, wherein the plurality of CAN components are high-speed data components.

16. The communication system of claim 15, wherein the high-speed data components operate over a high-frequency transmission line requiring impedance matching termination for multiple node architectures.

17. The communication system of claim 14, wherein the electrical switching circuit includes a cable detection pin.

18. The communication system of claim 14, wherein the two end nodes require no information from any of the interim nodes.

19. The communication system of claim 14, wherein the two end nodes are provided with termination resistances without sensing any activity of the interim nodes.