Device and method for matching output impedance in signal transmission system Number:7,164,286 from the United States Patent and Trademark Office (PTO) owispatent A signal transmission system includes a transmitter and a receiver connected via a transmission line. When a control circuit 103 in the transmitter 200 outputs a test signal to a transmission line 123, a voltage detection section 112 in the receiver 210 determines whether a voltage value on a terminal 115 falls within a given range or not. Based on the result, the control signal generation section 113 generates an instruction as to whether or not to change the current amount of the driving current. The control circuit 103 in the transmitter 100 drives the transmission line 123 with the driving current increased or decreased based on the instruction, and again outputs a test signal. This process is repeated until the voltage on the terminal 115 of the receiver 210 comes into the range. As a result, an optimum output impedance for the control circuit 103 of the transmitter 200 can be obtained. When transmitting a signal via the line, matching is dynamically established between the output impedance of the driving circuit and that of the line, whereby a fast signal transmission can be realized.<H transmission, impedance, Device, and, meth, 7164286.html, Patent, pto, 7164286

Title: Device and method for matching output impedance in signal transmission system

Abstract: A signal transmission system includes a transmitter and a receiver connected via a transmission line. When a control circuit 103 in the transmitter 200 outputs a test signal to a transmission line 123, a voltage detection section 112 in the receiver 210 determines whether a voltage value on a terminal 115 falls within a given range or not. Based on the result, the control signal generation section 113 generates an instruction as to whether or not to change the current amount of the driving current. The control circuit 103 in the transmitter 100 drives the transmission line 123 with the driving current increased or decreased based on the instruction, and again outputs a test signal. This process is repeated until the voltage on the terminal 115 of the receiver 210 comes into the range. As a result, an optimum output impedance for the control circuit 103 of the transmitter 200 can be obtained. When transmitting a signal via the line, matching is dynamically established between the output impedance of the driving circuit and that of the line, whereby a fast signal transmission can be realized.

Patent Number: 7,164,286 Issued on 01/16/2007 to Yaguchi

Inventors: Yaguchi; Yoshitaka (Takatsuki, JP)
Assignee: Matsushita Electric Industrial Co., Ltd. (Kadoma, JP)

Appl. No.: 10/560,797

Filed: June 18, 2004

PCT Filed: June 18, 2004

PCT No.: PCT/JP2004/008962

371(c)(1),(2),(4) Date: December 15, 2005

PCT Pub. No.: WO20/04/114522

PCT Pub. Date: December 29, 2004

Foreign Application Priority Data


Jun 24, 2003 [JP]			2003-179738

Current U.S. Class: 326/30 ; 326/31

Current International Class: H03K 19/003 (20060101)

Field of Search: 326/30-31,33-34,26-27

References Cited [Referenced By]

U.S. Patent Documents


5585741	December 1996	Jordan
6487250	November 2002	Kato et al.
2001/0015882	August 2001	Yanagawa

Foreign Patent Documents


10-50070	Feb., 1998	JP
10-261948	Sep., 1998	JP
11-017518	Jan., 1999	JP
2001-127614	May., 2001	JP
2003-008419	Jan., 2003	JP
2003-008421	Jan., 2003	JP

Other References

International Search Report for corresponding Application No. PCT/JP2004/008962, mailed Jul. 27, 2004. cited by other.

Primary Examiner: Cho; James H.
Attorney, Agent or Firm: Renner, Otto, Boisselle & Sklar, LLP

Claims

The invention claimed is:

1. A transmitter to be connected to a receiver via a transmission line, the transmitter composing a signal transmission system together with the receiver, the transmitter comprising: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing current amount of the driving current based on a control signal, wherein, as the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not.

2. The transmitter of claim 1, wherein, if the signal value falls within the predetermined range, the communication section receives as the control signal an instruction signal instructing to stop changing the current amount of the driving current, and based on the control signal, the driving current control section retains a present setting value of the current amount of the driving current.

3. The transmitter of claim 1, wherein, if the signal value is smaller than a lower limit value of the predetermined range, the communication section receives as the control signal an instruction signal instructing to increase the driving current, and based on the control signal, the driving current control section increases the driving current.

4. The transmitter of claim 1, wherein, if the signal value is greater than an upper limit value of the predetermined range, the communication section receives as the control signal an instruction signal instructing to decrease the driving current, and based on the control signal, the driving current control section decreases the driving current.

5. The transmitter of claim 1, wherein the communication section includes a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

6. The transmitter of claim 1, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal are performed by time division.

7. The transmitter of claim 1, wherein an output impedance value when the driving current control section drives the transmission line is smaller than an output impedance value of the receiver outputting the instruction signal.

8. The transmitter of claim 1, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal is faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

9. The transmitter of claim 1, wherein the transmission line is detachable from the communication section.

10. A receiver to be connected to a transmitter via a transmission line, the receiver composing a signal transmission system together with the transmitter, the transmitter being connected to a first end of the transmission line, the receiver comprising: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change current amount of the driving current, wherein the communication section outputs the instruction signal to the transmitter.

11. The receiver of claim 10, wherein, if a detection signal indicating that the signal value falls within the predetermined range is generated by the detection section, the signal generation section generates an instruction signal instructing to stop changing the current amount of the driving current.

12. The receiver of claim 10, wherein if a detection signal indicating that the signal value is smaller than a lower limit value of the predetermined range is generated by the detection section, the signal generation section generates an instruction signal instructing to increase the driving current.

13. The receiver of claim 10, wherein if a detection signal indicating that the signal value is greater than an upper limit value of the predetermined range is generated by the detection section, the signal generation section generates an instruction signal instructing to decrease the driving current.

14. The receiver of claim 10, wherein the communication section includes a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

15. The receiver of claim 10, wherein, the transmitter is capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal are performed by time division.

16. The receiver of claim 10, wherein an output impedance value of the transmitter driving the transmission line with the predetermined driving current is smaller than an output impedance value from the terminal portion to the signal generation section.

17. The receiver of claim 10, wherein a rate with which a signal is transmitted when the receiver outputs the instruction signal is slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

18. The receiver of claim 10, wherein the transmission line is detachable from the communication section.

19. A transmitting-end interface to be used in a transmitter to be connected to a receiving-end interface of a receiver via a transmission line, the transmitter composing a signal transmission system together with the receiver, the transmitting-end interface comprising: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing current amount of the driving current based on a control signal, wherein, as the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not.

20. The transmitting-end interface of claim 19, wherein the communication section includes a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

21. The transmitting-end interface of claim 19, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal are performed by time division.

22. The transmitting-end interface of claim 19, wherein an output impedance value when the driving current control section drives the transmission line is smaller than an output impedance value of the receiver outputting the instruction signal.

23. The transmitting-end interface of claim 19, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal is faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

24. A receiving-end interface to be used in a receiver to be connected to a transmitting-end interface of a transmitter via a transmission line, the receiver composing a signal transmission system together with the transmitter, the transmitting-end interface being connected to a first end of the transmission line, the receiving-end interface comprising: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal received at the communication section, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change current amount of the driving current, wherein the communication section outputs the instruction signal to the transmitter.

25. The receiving-end interface of claim 24, wherein the communication section includes a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

26. The receiving-end interface of claim 24, wherein, the transmitter is capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal are performed by time division.

27. The receiving-end interface of claim 24, wherein an output impedance value of the transmitter driving the transmission line with the predetermined driving current is smaller than an output impedance value from the terminal portion to the signal generation section.

28. The receiving-end interface of claim 24, wherein a rate with which a signal is transmitted when the receiving-end interface outputs the instruction signal is slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

29. An interface system comprising a transmitting-end interface to be used in a transmitter and a receiving-end interface to be used in a receiver, the transmitting-end interface and the receiving-end interface being connected via a transmission line, the transmitter and the receiver composing a signal transmission system, wherein the transmitting-end interface comprises: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing current amount of the driving current based on a control signal, wherein the receiving-end interface comprises: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with the predetermined amount of driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal received at the communication section, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not, the instruction signal to be output by the communication section of the receiving-end interface, and wherein, as the control signal, the communication section of the transmitting-end interface receives from the receiver the instruction signal.

30. A transmitting-end chip to be connected to a receiving-end chip via a transmission line, the transmitting-end chip composing a signal transmission system together with the receiving-end chip, the transmitting-end chip comprising: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing current amount of the driving current based on a control signal, wherein, as the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not.

31. The transmitting-end chip of claim 30, wherein the communication section includes a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

32. The transmitting-end chip of claim 30, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal are performed by time division.

33. The transmitting-end chip of claim 30, wherein an output impedance value when the driving current control section drives the transmission line is smaller than an output impedance value of the receiver outputting the instruction signal.

34. The transmitting-end chip of claim 30, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal is faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

35. A receiving-end chip to be connected to a transmitting-end chip via a transmission line, the receiving-end chip composing a signal transmission system together with the transmitting-end chip, the transmitting-end chip being connected to a first end of the transmission line, the receiving-end chip comprising: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal received at the communication section, generating an instruction signal for instructing whether or not to change current amount of the driving current, wherein the communication section outputs the instruction signal to the transmitter.

36. The receiving-end chip of claim 35, wherein the communication section includes a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

37. The receiving-end chip of claim 35, wherein, the transmitter is capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal are performed by time division.

38. The receiving-end chip of claim 35, wherein an output impedance value of the transmitter driving the transmission line with the predetermined driving current is smaller than an output impedance value from the terminal portion to the signal generation section.

39. The receiving-end chip of claim 35, wherein a rate with which a signal is transmitted when the receiving-end chip outputs the instruction signal is slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

40. A chip-mounted board comprising a transmitting-end chip of and a receiving-end chip, the transmitting-end chip and the receiving-end chip being connected via the transmission line, wherein the transmitting-end chip comprises: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing current amount of the driving current based on a control signal, wherein the receiving-end chip comprises: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with the predetermined amount of driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not, the instruction signal to be output by the communication section of the receiving-end chip, and wherein, as the control signal, the communication section of the transmitting-end chip receives from the receiving-end chip the instruction signal.

41. An impedance matching method for setting an output impedance of a transmitter which is connected to a receiver via a transmission line and composes a signal transmission system together with the receiver, the transmitter including: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line, the receiver being connected to a second end of the transmission line, the method comprising the steps of: operating the driving current control section to drive the transmission line with a predetermined amount of driving current; receiving, as a control signal for instructing whether or not to change the current amount of the driving current, an instruction signal generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not; and changing the current amount of the driving current based on the control signal.

42. The impedance matching method of claim 41, wherein, the communication section includes a first terminal connected to the first end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the step of receiving receives the instruction signal at the second terminal.

43. The impedance matching method of claim 41, wherein, the step of driving operates the driving current control section to transmit a signal by driving the transmission line, and wherein the method further comprises a step of performing, by time division, transmission of a signal from the driving current control section and reception of the control signal.

44. The impedance matching method of claim 41, wherein an output impedance value when the driving current control section drives the transmission line is smaller than an output impedance value of the receiver outputting the instruction signal.

45. The impedance matching method of claim 41, wherein, the step of driving operates the driving current control section to transmit a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal is faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

46. An output impedance setting assisting method for, in a receiver which is connected to a transmitter via a transmission line and composes a signal transmission system together with the transmitter, assisting in setting an output impedance of the transmitter, the transmitter being connected to a first end of the transmission line, the receiver including: a communication section connected to a second end of the transmission line; and a detection section for detecting a signal value at a predetermined position, the method comprising the steps of: receiving, via the communication section, a signal from the transmission line being driven with a predetermined driving current; detecting, by using the detection section, a signal value at the second end of the transmission line based on the signal; generating a detection signal indicating whether the signal value falls within a predetermined range or not; based on the detection signal, determining whether or not to change the current amount of the driving current with which the transmission line is driven; generating an instruction signal indicating the result of determination; and outputting the instruction signal to the transmitter via the communication section.

47. The output impedance setting assisting method of claim 46, wherein, the communication section includes a first terminal connected to the second end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the step of receiving receives the instruction signal at the second terminal.

48. The output impedance setting assisting method of claim 46, wherein, the transmitter is capable of transmitting a signal by driving the transmission line with the predetermined driving current, and wherein the method further comprises a step of performing, by time division, reception of a signal from the transmission line and transmission of the instruction signal.

49. The output impedance setting assisting method of claim 46, wherein an output impedance value of the transmitter driving the transmission line with the predetermined driving current is smaller than an output impedance value from the terminal portion to the signal generation section.

50. The output impedance setting assisting method of claim 46, wherein a rate with which a signal is transmitted when the receiver outputs the instruction signal is slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

51. A product of a computer program, the computer program to be executed in a transmitter which is connected to a receiver via a transmission line and composes a signal transmission system together with the receiver, the transmitter including: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line, the receiver being connected to a second end of the transmission line, the computer program comprising the steps of: operating the driving current control section to drive the transmission line with a predetermined amount of driving current; causing the communication section to receive, as a control signal for instructing whether or not to change the current amount of the driving current, an instruction signal generated at the receiver based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not; and changing the current amount of the driving current based on the control signal.

52. The product of a computer program of claim 51, wherein, the communication section includes a first terminal connected to the first end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the instruction signal is received at the second terminal.

53. The product of a computer program of claim 51, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line, and the transmitter is caused to perform, by time division, transmission of a signal from the driving current control section and reception of the control signal.

54. The product of a computer program of claim 51, wherein an output impedance value when the driving current control section drives the transmission line is smaller than an output impedance value of the receiver outputting the instruction signal.

55. The product of a computer program of claim 51, wherein, the driving current control section is capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal is faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

56. A product of a computer program, the computer program to be executed in a receiver which is connected to a transmitter via a transmission line and composes a signal transmission system together with the transmitter, the transmitter being connected to a first end of the transmission line, the receiver including: a communication section connected to a second end of the transmission line; and a detection section for detecting a signal value at a predetermined position, the computer program comprising the steps of: receiving, via the communication section, a signal from the transmission line being driven with a predetermined driving current; detecting, by using the detection section, a signal value at the second end of the transmission line based on the signal; generating a detection signal indicating whether the signal value falls within a predetermined range or not; based on the detection signal, determining whether or not to change the current amount of the driving current with which the transmission line is driven; generating an instruction signal indicating the result of determination; and outputting the instruction signal to the transmitter via the communication section.

57. The product of a computer program of claim 56, wherein, the communication section includes a first terminal connected to the second end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the instruction signal is received at the second terminal.

58. The product of a computer program of claim 56, wherein, the transmitter is capable of transmitting a signal by driving the transmission line with the predetermined driving current, and the receiver is caused to perform, by time division, reception of a signal from the transmission line and transmission of the instruction signal.

59. The product of a computer program of claim 56, wherein an output impedance value of the transmitter driving the transmission line with the predetermined driving current is smaller than an output impedance value from the terminal portion to the signal generation section.

60. The product of a computer program of claim 56, wherein a rate with which a signal is transmitted when the receiver outputs the instruction signal is slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

Description

TECHNICAL FIELD

The present invention relates to a technique of, when transmitting a signal between devices which are connected via a transmission line, establishing matching between the output impedance of a driving circuit for driving the transmission line and the impedance of the transmission line. In particular, the present invention relates to a technique of output impedance adjustment for reducing waveform distortion caused by reflection at the time of signal transmission, and transmission of a waveform distortion detection signal.

BACKGROUND ART

When transmitting a signal between home appliances which are connected via a cable, or between semiconductor integrated circuits on a board that are connected via printed wiring, it is necessary to establish matching between the output impedance of the driving circuit and the impedance of the transmission line. The reason is that, if matching is not established, waveform distortion will occur due to reflection of the transmitted signal, thus hindering correct transmission of the signal. Furthermore, extra time is required until the signal reflection becomes subsided, thus making fast signal transmission difficult.

Conventionally, various methods for establishing matching between the output impedance of a driving circuit at the signal-transmitting end and the impedance of a transmission line have been known. Japanese Laid-Open Patent Publication No. 2003-8419, Japanese Laid-Open Patent Publication No. 10-261948, and Japanese Laid-Open Patent Publication No. 11-17518 describe techniques of establishing impedance matching when transmitting a signal between semiconductor integrated circuits. To describe the content of Japanese Laid-Open Patent Publication No. 2003-8419 as an example, separately in addition to a transmission line used for actual signal transmission, a reference transmission line is provided in loop fashion and terminated at the semiconductor integrated circuit which outputs a signal, the reference transmission line having equivalent characteristics to those of the transmission line. By utilizing the reference transmission line to establish matching between the output impedance of the driving circuit and the impedance of the transmission line, it is considered that impedance matching is also established with respect to the actual transmission line.

However, the conventional impedance matching techniques have various problems.

A first problem is that there may be an error between the characteristics of the transmission line which is used for transmitting an actual signal and the characteristics of the reference transmission line. In the case where the transmission line is a printed wiring board, naturally, the transmission line used for transmitting an actual signal and the reference transmission line are to be disposed at different positions on the printed wiring board. Even on the same printed wiring board, depending on the position, there may be variations in the characteristics (dielectric constant and the like) which determine impedance. Therefore, even if impedance matching is established by using the reference transmission line, optimal matching cannot be guaranteed with respect to the impedance of the actual transmission line. In other words, even by using the reference transmission line, it is difficult to determine the optimum impedance of the actual transmission line.

A second problem is that, since the reference transmission line must be provided separately in addition to the transmission line used for transmitting an actual signal, increases in area and volume may result. Especially in the case where there are plural signal transmission lines, and where precise impedance matching must be established, the same number or a close number of reference wiring patterns will have to be provided corresponding to the plural transmission lines, thus resulting in a great increase in wiring area. Such would be contrary to the trend for chip downsizing in the recent years, and therefore is impractical.

A third problem is that the aforementioned impedance matching techniques are not applicable to impedance matching between home appliance devices which are connected via a cable. In the case where a personal computer (PC) and a USB device are to be connected via a USB cable, for example, it will be impossible and impractical to provide a reference transmission line. Moreover, since the home appliance devices to be connected are diversified and it is impossible to establish impedance matching in advance, it will be necessary to establish impedance matching in a dynamic manner upon each connection. Especially in the case where signals are to be rapidly transmitted between home appliance devices, if matching between the impedance of a driving circuit and the impedance of a cable cannot be established, fast transmission may not be possible depending on the particular cable used, thus detracting from reliability.

An objective of the present invention is to, when transmitting a signal via a transmission line, establish matching between the output impedance of a driving circuit and the impedance of the transmission line in a dynamic manner, thus realizing fast signal transmission and improving transmission efficiency. Another objective of the present invention is to adapt the power consumption at the time of signal transmission to the transmission line, thus reducing power consumption to the bear minimum.

DISCLOSURE OF INVENTION

A transmitter according to the present invention is to be connected to a receiver via a transmission line, the transmitter composing a signal transmission system together with the receiver. The transmitter includes: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing the current amount of the driving current based on a control signal. As the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not. Thus, the aforementioned objectives are attained.

If the signal value falls within the predetermined range, the communication section may receive as the control signal an instruction signal instructing to stop changing the current amount of the driving current, and based on the control signal, the driving current control section may retain a present setting value of the current amount of the driving current.

If the signal value is smaller than a lower limit value of the predetermined range, the communication section may receive as the control signal an instruction signal instructing to increase the driving current, and based on the control signal, the driving current control section may increase the driving current.

If the signal value is greater than an upper limit value of the predetermined range, the communication section may receive as the control signal an instruction signal instructing to decrease the driving current, and based on the control signal, the driving current control section may decrease the driving current.

The communication section may include a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal may be performed by time division.

An output impedance value when the driving current control section drives the transmission line may be smaller than an output impedance value of the receiver outputting the instruction signal.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal may be faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

The transmission line may be detachable from the communication section.

A receiver according to the present invention is to be connected to a transmitter via a transmission line, the receiver composing a signal transmission system together with the transmitter. The transmitter is connected to a first end of the transmission line. The receiver includes: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change the current amount of the driving current. The communication section outputs the instruction signal to the transmitter. Thus, the aforementioned objectives are attained.

If a detection signal indicating that the signal value falls within the predetermined range is generated by the detection section, the signal generation section may generate an instruction signal instructing to stop changing the current amount of the driving current.

If a detection signal indicating that the signal value is smaller than a lower limit value of the predetermined range is generated by the detection section, the signal generation section may generate an instruction signal instructing to increase the driving current.

If a detection signal indicating that the signal value is greater than an upper limit value of the predetermined range is generated by the detection section, the signal generation section may generate an instruction signal instructing to decrease the driving current.

The communication section may include a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

The transmitter may be capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal may be performed by time division.

An output impedance value of the transmitter driving the transmission line with the predetermined driving current may be smaller than an output impedance value from the terminal portion to the signal generation section.

A rate with which a signal is transmitted when the receiver outputs the instruction signal may be slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

The transmission line may be detachable from the communication section.

A transmitting-end interface according to the present invention is to be used in a transmitter to be connected to a receiving-end interface of a receiver via a transmission line, the transmitter composing a signal transmission system together with the receiver. The transmitting-end interface includes: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing the current amount of the driving current based on a control signal. As the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal may be performed by time division.

An output impedance value when the driving current control section drives the transmission line may be smaller than an output impedance value of the receiver outputting the instruction signal.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal may be faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

A receiving-end interface according to the present invention is to be used in a receiver to be connected to a transmitting-end interface of a transmitter via a transmission line, the receiver composing a signal transmission system together with the transmitter. The transmitting-end interface is connected to a first end of the transmission line. The receiving-end interface includes: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal received at the communication section, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal, generating an instruction signal for instructing whether or not to change the current amount of the driving current. The communication section outputs the instruction signal to the transmitter. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

The transmitter may be capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal may be performed by time division.

An output impedance value of the transmitter driving the transmission line with the predetermined driving current may be smaller than an output impedance value from the terminal portion to the signal generation section.

A rate with which a signal is transmitted when the receiving-end interface outputs the instruction signal may be slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

An interface system comprising the aforementioned transmitting-end interface and the aforementioned receiving-end interface may be constructed, wherein the transmitting-end interface and the receiving-end interface are connected via the transmission line.

A transmitting-end chip according to the present invention is to be connected to a receiving-end chip via a transmission line, the transmitting-end chip composing a signal transmission system together with the receiving-end chip. The transmitting-end chip includes: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line with a predetermined amount of driving current, the driving current control section changing the current amount of the driving current based on a control signal. As the control signal, the communication section receives from the receiver being connected to a second end of the transmission line an instruction signal for instructing whether or not to change the current amount of the driving current, the instruction signal being generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the first end of the transmission line and a second terminal for being connected to a control signal line to receive the instruction signal, the control signal line being different from the transmission line.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and transmission of a signal from the driving current control section and reception of the control signal may be performed by time division.

An output impedance value when the driving current control section drives the transmission line may be smaller than an output impedance value of the receiver outputting the instruction signal.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal may be faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

A receiving-end chip according to the present invention is to be connected to a transmitting-end chip via a transmission line, the receiving-end chip composing a signal transmission system together with the transmitting-end chip. The transmitting-end chip is connected to a first end of the transmission line. The receiving-end chip includes: a communication section connected to a second end of the transmission line, the communication section receiving a signal from the transmission line being driven with a predetermined driving current; a detection section for detecting a signal value at the second end of the transmission line based on the signal, and for generating a detection signal indicating whether the signal value falls within a predetermined range or not; and a signal generation section for, based on the detection signal received at the communication section, generating an instruction signal for instructing whether or not to change the current amount of the driving current. The communication section outputs the instruction signal to the transmitter. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the second end of the transmission line and a second terminal for being connected to a control signal line to output the instruction signal, the control signal line being different from the transmission line.

The transmitter may be capable of transmitting a signal by driving the transmission line with the predetermined driving current; and reception of a signal from the transmission line and transmission of the instruction signal may be performed by time division.

An output impedance value of the transmitter driving the transmission line with the predetermined driving current may be smaller than an output impedance value from the terminal portion to the signal generation section.

A rate with which a signal is transmitted when the receiving-end chip outputs the instruction signal may be slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

A chip-mounted board comprising the aforementioned transmitting-end chip and the aforementioned receiving-end chip may be constructed, wherein the transmitting-end chip and the receiving-end chip are connected via the transmission line.

An output impedance setting method according to the present invention sets an output impedance of a transmitter which is connected to a receiver via a transmission line and composes a signal transmission system together with the receiver. The transmitter includes: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line, the receiver being connected to a second end of the transmission line. The method includes the steps of: operating the driving current control section to drive the transmission line with a predetermined amount of driving current; receiving, as a control signal for instructing whether or not to change the current amount of the driving current, an instruction signal generated based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not; and changing the current amount of the driving current based on the control signal. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the first end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the step of receiving may receive the instruction signal at the second terminal.

The step of driving may operate the driving current control section to transmit a signal by driving the transmission line, and a step of performing, by time division, transmission of a signal from the driving current control section and reception of the control signal may be further comprised.

An output impedance value when the driving current control section drives the transmission line may be smaller than an output impedance value of the receiver outputting the instruction signal.

The step of driving may operate the driving current control section to transmit a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal may be faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

An output impedance setting, assisting method according to the present invention is to be used in a receiver which is connected to a transmitter via a transmission line and composes a signal transmission system together with the transmitter. The transmitter is connected to a first end of the transmission line, the receiver including: a communication section connected to a second end of the transmission line; and a detection section for detecting a signal value at a predetermined position. The method includes the steps of: receiving, via the communication section, a signal from the transmission line being driven with a predetermined driving current; detecting, by using the detection section, a signal value at the second end of the transmission line based on the signal; generating a detection signal indicating whether the signal value falls within a predetermined range or not; based on the detection signal, determining whether or not to change the current amount of the driving current with which the transmission line is driven; generating an instruction signal indicating the result of determination; and outputting the instruction signal to the transmitter via the communication section. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the second end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the step of receiving may receive the instruction signal at the second terminal.

The transmitter may be capable of transmitting a signal by driving the transmission line with the predetermined driving current, and a step of performing, by time division, reception of a signal from the transmission line and transmission of the instruction signal may be further comprised.

An output impedance value of the transmitter driving the transmission line with the predetermined driving current may be smaller than an output impedance value from the terminal portion to the signal generation section.

A rate with which a signal is transmitted when the receiver outputs the instruction signal may be slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

A computer program according to the present invention is to be executed in a transmitter which is connected to a receiver via a transmission line and composes a signal transmission system together with the receiver. The transmitter includes: a communication section to be connected to a first end of the transmission line; and a driving current control section for driving the transmission line, the receiver being connected to a second end of the transmission line. The computer program includes the steps of: operating the driving current control section to drive the transmission line with a predetermined amount of driving current; receiving of causing the communication section to receive, as a control signal for instructing whether or not to change the current amount of the driving current, an instruction signal generated at the receiver based on whether a signal value detected at the second end of the transmission line falls within a predetermined range or not; and changing the current amount of the driving current based on the control signal. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the first end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the instruction signal may be received at the second terminal.

The driving current control section may be capable of transmitting a signal by driving the transmission line, and the transmitter may be caused to perform, by time division, transmission of a signal from the driving current control section and reception of the control signal.

An output impedance value when the driving current control section drives the transmission line may be smaller than an output impedance value of the receiver outputting the instruction signal.

The driving current control section may be capable of transmitting a signal by driving the transmission line; and a rate with which the driving current control section transmits a signal may be faster than a rate with which a signal is transmitted when the receiver outputs the instruction signal.

A computer program according to the present invention is to be executed in a receiver which is connected to a transmitter via a transmission line and composes a signal transmission system together with the transmitter. The transmitter is connected to a first end of the transmission line, the receiver including: a communication section connected to a second end of the transmission line; and a detection section for detecting a signal value at a predetermined position. The computer program includes the steps of: receiving, via the communication section, a signal from the transmission line being driven with a predetermined driving current; detecting, by using the detection section, a signal value at the second end of the transmission line based on the signal; generating a detection signal indicating whether the signal value falls within a predetermined range or not; based on the detection signal, determining whether or not to change the current amount of the driving current with which the transmission line is driven; generating an instruction signal indicating the result of determination; and outputting the instruction signal to the transmitter via the communication section. Thus, the aforementioned objectives are attained.

The communication section may include a first terminal connected to the second end of the transmission line and a second terminal connected to a control signal line, the control signal line being different from the transmission line; and the instruction signal may be received at the second terminal.

The transmitter may be capable of transmitting a signal by driving the transmission line with the predetermined driving current, and the receiver may be caused to perform, by time division, reception of a signal from the transmission line and transmission of the instruction signal.

An output impedance value of the transmitter driving the transmission line with the predetermined driving current may be smaller than an output impedance value from the terminal portion to the signal generation section.

A rate with which a signal is transmitted when the receiver outputs the instruction signal may be slower than a rate with which the driving current control section transmits a signal by driving the transmission line.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a) and (b) show variations of signal transmission systems 1, where (a) is a diagram showing the constitution of a signal transmission system 1 having a PC 100 and a hard disk drive 110, and FIG. 1(b) is a diag