Active bus termination device

• US 5,442,305 A
• Filed: 09/14/1994
• Issued: 08/15/1995
• Est. Priority Date: 10/03/1991
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Martin, Stephen R., Mooney, Randall O. Jr.
• Primary Examiner(s): Hudspeth, David R.
• Application Number:
  US08/306,010
• Time in Patent Office: 335 Days
• Field of Search: 326/30-31, 326/38
• US Class Current: 326/30
• CPC Class Codes: G01R 31/31915 In-circuit Testers
• CPC Class Codes: G06F 11/22 Detection or location of defective computer hardware by testing during standby operation or during idle time, e.g. start-up testing
• CPC Class Codes: G06F 11/221 to test buses, lines or interfaces, e.g. stuck-at or open line faults
• CPC Class Codes: G06F 11/2294 by remote test
• CPC Class Codes: G06F 11/261 by simulating additional hardware, e.g. fault simulation
• CPC Class Codes: G06F 11/2736 using a dedicated service processor for test

Abstract

A diagnostic apparatus for testing devices such as computer systems, and computer system components such as disk drives or printers. The device comprises a main unit, the main unit having a central processing unit for executing instructions, issuing commands, and receiving data from a first device. The apparatus also has a first peripheral unit coupled to the main unit, the first peripheral unit having ports for interfacing with the first device, the first peripheral unit being interchangeable with a second peripheral unit for interfacing with a second device. The apparatus also comprises a first non-volatile memory unit coupled to the main unit. The first non-volatile memory unit comprising a first set of tests for the first device, the first non-volatile memory unit being interchangeable with a second non-volatile memory unit comprising a second set of tests for a second device. These interchangeable parts are provided so that the user may test various types of hardware. The apparatus further comprises software means for providing termination on a bus and methods for simulating devices on a bus for remote entry into diagnostic programs.

Claims

1. A device for terminating a bus comprising:

a. first means for activating termination of the bus;

b. second means coupled to the first means for supplying power, the second means supplying power upon activation of the first means;

c. third means coupled to the second means for limiting voltage received from the second means; and

d. fourth means coupled to the third means for limiting transient voltages on the bus.

2. The device of claim 1 wherein the first means comprises a flag.

3. The device of claim 1 wherein tile second means comprises a MOS-FET wherein the source of the MOS-FET coupled to a power supply, drain is coupled to the third means, and tile gate is coupled to the first means.

4. The device of claim 1 wherein the third means comprises a low dropout voltage regulator.

5. The device of claim 1 wherein the fourth means comprises at least one diode.