System and method for terminating a bus

• US 6,970,953 B2
• Filed: 01/04/2002
• Issued: 11/29/2005
• Est. Priority Date: 01/04/2002
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Osuna, Ricardo, Gregory, Paul E.
• Primary Examiner(s): Gaffin, Jeffrey
• Assistant Examiner(s): KIM, HAROLD J
• Application Number:
  US10/039,106
• Publication Number:
  US 20030131159A1
• Time in Patent Office: 1,425 Days
• Field of Search: 710/15, 710/32, 710/62, 710/200, 710/300, 710/104, 710/106
• US Class Current: 710/15
• CPC Class Codes: G06F 13/4086 Bus impedance matching, e.g. termination
• CPC Class Codes: H04L 12/40019 Details regarding a bus master
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

An exemplary system includes a bus (such as CAN bus) having at least two end points. A first and/or a second set of an undetermined number of devices may be connected to the bus. A controller is also connected to the bus, and is configured to establish a termination of the bus at one of the end points relative to the first and second sets of devices, dependent upon whether the controller receives a reply message in response to a communication test message sent to the first and second sets of devices at different times. If the controller discovers that devices are connected to the bus in both sets, the controller is relieved of establishing an end point on either end of the bus. Otherwise, if the controller discovers that devices are only connected to the bus in one of the two sets, the controller is therefore, configured to terminate an end of the bus.

Claims

1. A method of terminating a bus comprising:

activating a termination load across a controller device;

enabling a first set of potential devices connected to said bus;

attempting to establish communication with any of said first set of potential devices;

deactivating said termination load across said controller device, if communication is established between said controller and at least one of said potential devices in said first set of potential devices;

enabling a second set of potential devices connected to said bus;

attempting to establish communication with any of said second set of potential devices; and

reactivating said termination load across said controller device, if communication is not established between said controller and at least one of said potential devices in said second set of devices.

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

leaving enabled said first set of potential devices while attempting to establish communication with any of said second set of potential devices.

3. The method as recited in claim 1, wherein said termination load is a resistor coupled in parallel to said controller and is activated and deactivated by a switch controlled by said controller.

4. The method as recited in claim 1, wherein said bus is a CAN bus.

5. The method as recited in claim 1, wherein said controller is a paper handling controller for a printer device.

6. The method as recited in claim 1, wherein said first set of potential devices includes at least one paper handling device.

7. The method as recited in claim 1, wherein said second set of potential devices includes at least one paper handling device.