System for reducing distortion of signals transmitted over a bus

• US 20020173925A1
• Filed: 03/29/2002
• Published: 11/21/2002
• Est. Priority Date: 03/30/2001
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sugawara, Takashi, Komiyama, Hirohide
• Granted Patent: US 6,778,930 B2
• Time in Patent Office: Days
• US Class Current: 702/107
• CPC Class Codes: G06F 13/4086 Bus impedance matching, e.g. termination

Abstract

A computer system measures bus signal distortion and then adjusts certain characteristics of the signal transmitted over the bus, or adjusts other characteristics of the bus or the load on the bus so that signal distortion is reduced. Distortion characteristics that may be measured include signal voltage overshoot and undershoot, and data setup and hold times. Characteristics of the signal and the system that may be adjusted include changing the slew rate of the signal, changing the data setup and hold times, and changing the load impedance on the bus.

Claims

1. A data processing system, comprising:

a bus;

a signal transmitter for transmitting a data signal over said bus;

a signal receiver for receiving the data signal transmitted by said signal transmitter over said bus;

a signal diagnostic unit for detecting a distortion in the signal; and

an adjustment unit for adjusting a characteristic of the data processing system in response to the distortion detected by said signal diagnostic unit.

2. The data processing system of claim 1, wherein the characteristic of the data processing system adjusted by said adjustment unit includes a slew rate of the signal as transmitted by said signal transmitter.

3. The data processing system of claim 1, wherein the characteristic of the data processing system adjusted by said adjustment unit includes a resistance value of a terminating resistor provided in one or both of said signal transmitter and said signal receiver.

4. The data processing system of claim 1 wherein:

said signal transmitter includes said signal diagnostic unit and said adjustment unit; and

further comprising a feedback circuit coupled between said signal receiver and said signal transmitter for feeding back the signal as received by said signal receiver to said signal transmitter, wherein said signal diagnostic unit detects distortion in the signal as received from said feedback circuit.

5. The data processing system of claim 1, wherein:

said signal receiver includes said signal diagnostic unit, said signal diagnostic unit detecting distortion in the signal as received by said signal receiver; and

said signal transmitter includes said adjustment unit.

6. The data transfer apparatus of claim 5, wherein said diagnostic unit transfers a command over said bus to said adjustment unit, said commend being indicative of the distortion detected by said diagnostic unit;

and

wherein said adjustment unit adjusts the characteristic of the data processing system in response to said command.

7. The data processing system of claim 5, further comprising a diagnostic information transfer circuit disposed between said signal diagnostic unit and said adjustment unit, for transferring to said adjustment unit a signal indicative of the distortion detected by said signal diagnostic unit.

8. The data processing system of claim 5, further comprising:

a diagnostic information storage memory in which diagnostic information produced by said signal diagnostic unit is stored;

a signal characteristic information storage memory in which information about a characteristic of the signal transmitted by said signal transmitter is stored; and

a signal characteristic information update unit for reading said diagnostic information from said diagnostic information storage memory and for updating information stored in said signal characteristic information storage memory based on said diagnostic information.

9. A computer system comprising:

a bus;

a host device including a signal transmitter for transmitting a signal over said bus, and further including a slew rate adjustment unit for adjusting the slew rate of the signal as transmitted by said signal transmitter;

a peripheral device including a signal receiver for receiving signals transmitted over said bus by said signal transmitter; and

a signal waveform diagnostic unit for detecting distortion in the signal as received by said signal receiver.

10. The computer system of claim 9, wherein said peripheral device comprises:

a peripheral device side signal transmission part for transmitting a signal to said bus; and

a peripheral device side slew rate adjustment part for adjusting a slew rate of the signal transmitted from said device side signal transmission part;

said host device comprises a host side signal reception part for receiving the signal from said bus, and

said system further comprises a host side signal waveform diagnostic part for detecting a distortion in the signal received by the host side signal reception part.

11. The computer system of claim 9, wherein said signal waveform diagnostic part comprises a circuit for detecting at least one of an undershoot, an overshoot, a data setup time, and a data hold margin of said signal.

12. The computer system of claim 9, wherein said host part further comprises a calibration execution part for executing with a predetermined time a calibration process to adjust with said slew rate adjustment part the slew rate of the signal transmitted by said signal transmission part, by transmitting a predetermined signal from said signal transmission part of the host part and diagnosing with said signal waveform diagnostic part the waveform of the signal received by said signal reception part of said peripheral device.

13. The computer system of claim 12, wherein said peripheral device can be removably attached to said bus, and said calibration execution part executes said calibration process upon detection of attachment of said peripheral device to said bus.

15. The computer system of claim 14, wherein a peripheral device is attached to said interface and comprises a waveform diagnostic part for detecting distortion in the signal that is outputted from said host part.

16. The computer system of claim 14, further comprising:

a docking station, said docking station including a docking station bus connected to said bus through said interface;

a docking station connector for attaching said peripheral device to said docking station bus; and

a waveform diagnostic part for detecting distortion in the signal transmitted by said host part through said bus and received on said docking station bus.

14. A computer system comprising:

a host part;

a bus for transferring a data signal; and

an interface for attaching a peripheral device to said bus,

wherein said host part adjusts a slew rate of the signal based on the waveform of the signal as detected at said interface.

17. A device for attachment to a computer system comprising:

a waveform diagnostic part for diagnosing a waveform of a signal that is transmitted from a bus provided in the computer system and is received by said device; and

a correction information output part for delivering information for correcting the waveform of the signal received by said device, to the computer system based on a diagnosis by said waveform diagnostic part.

18. A docking station for removable attachment to a computer system, said docking station comprising:

a docking bus connectable to a computer bus provided in the computer system;

a waveform diagnostic part for diagnosing a waveform of a signal transmitted from the compter bus and received on said docking bus; and

a correction information output part for delivering information for correcting the waveform of the signal that is outputted from said bus, to the computer system based on a diagnosis by said waveform diagnosis part.