Cable tester with indicator

• US 6,977,507 B1
• Filed: 12/30/2002
• Issued: 12/20/2005
• Est. Priority Date: 06/07/2002
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Lo, William, Guo, Yiqing, Pannell, Donald
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Dole, Timothy J.
• Application Number:
  US10/331,221
• Time in Patent Office: 1,086 Days
• Field of Search: 324532-535, 324/522, 324/523, 324/527, 324/538
• US Class Current: 324/534
• CPC Class Codes: G01R 31/11 using pulse reflection methods
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72
• CPC Class Codes: H04M 3/28 Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor

Abstract

A system comprises a physical layer device that is adapted to communicate with a cable medium and that includes a first input/output terminal. A first transceiver communicates with the first input/output terminal and the cable medium. A cable tester tests the cable medium and determines a cable status. An indicator communciates with the physical layer device and identifies at least one of link presence, link abscence, link activity, link duplex and or link speed of the first input/output terminal during normal operation. The cable tester also uses the indicator to indicate at least one of cable testing status during the test and/or the cable status after the test.

Claims

1. A system comprising:

a physical layer device that is adapted to communicate with a cable medium and that includes;

a first input/output terminal;

a first transceiver that communicates with said first input/output terminal and the cable medium; and

a cable tester that tests the cable medium and determines a cable status; and

an indicator that communicates with said physical layer device and that identifies at least one of link presence, link absence, link activity, link duplex and/or link speed of said first input/output terminal during normal operation,

wherein said cable tester also uses the indicator to indicate at least one of cable testing status during said test and/or said cable status after said test.

2. The system of claim 1 wherein said cable tester includes a pretest module that senses activity on the cable medium and enables testing if activity is not detected for a first period, and a test module that is enabled by said pretest module, transmits a test pulse on the cable medium, measures a reflection amplitude and calculates a cable length, wherein said cable tester determines said status based on said measured amplitude and said calculated cable length.

3. The system of claim 2 wherein said pretest module enables testing if, during said first period, activity is detected and is subsequently not detected for a second period after said activity is detected.

4. The system of claim 2 further comprising an analog to digital converter (ADC) that measures said reflection amplitude, wherein said test module measures offset at said ADC, subtracts said offset from said reflection amplitude, and zeroes said reflection amplitude below a floor, wherein said floor has a first value during a first period after said test pulse and a second value during a second period after said first period.

5. The system of claim 1 further comprising a lookup table that includes a plurality of sets of reflection amplitudes as a function of cable length, wherein said cable tester determines said cable status using said lookup table, said reflection amplitude and said cable length.

6. The system of claim 5 wherein said sets of reflection amplitudes define a plurality of windows including a first window that is defined by first and second thresholds, wherein said first threshold is based on a first set of reflection amplitudes that are measured as a function of cable length when a test cable type is an open circuit, and wherein said second threshold is based on a second set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a first impedance having a first impedance value.

7. The system of claim 6 wherein a second window is defined by third and fourth thresholds, wherein said third threshold is based on a third set of reflection amplitudes that are measured as a function of cable length when said test cable type is a short circuit, wherein said fourth threshold is based on a fourth set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a second impedance having a second impedance value.

8. The system of claim 7 wherein a third window is defined between said second and fourth thresholds.

9. The system of claim 8 wherein the cable medium is declared an open circuit when said reflection amplitude is in said first window for said cable length and wherein the cable medium is declared a short circuit when said reflection amplitude is in said second window for said cable length, and wherein the cable medium is declared normal when said reflection amplitude is in said third window for said cable length.

10. The system of claim 5 wherein said cable status includes good, open and short cable statuses.

11. The system of claim 1 wherein said physical layer device includes a plurality of input/output terminals and said cable tester includes a test actuator that triggers said test during operation of said physical layer device for unlinked input/output terminals but not linked input/output terminals.

12. The system of claim 1 wherein said cable tester enters a test fail status when the cable medium is active for a period greater than a test fail period.

13. The system of claim 1 wherein said cable tester is integrated with said transceiver in a single integrated circuit.

14. The system of claim 1 wherein the indicator includes at least one of an audio indicator and/or a visual indicator.

15. The system of claim 1 wherein the indicator includes at least one of a speaker, a light emitting diode (LED), and/or an incandescent light.

16. The system of claim 1 further comprising:

a detector that detects a power over Ethernet (POE) device;

a power supply; and

a switching device that selectively provides power from said power supply over the cable medium when said detector detects said POE device, wherein said cable tester delays testing of the cable medium when said detector detects said POE device until said switching device provides said power.

17. The system of claim 1 wherein said physical layer device forms part of one of a switch, a router, a computer, a laptop, a smart videocassette recorder, an IP telephone, a fax machine, a modem, a television, a stereo, or a hand-held device.

18. The system of claim 1 wherein said physical layer device is implemented in an Ethernet network device.

19. The system of claim 18 wherein said Ethernet network device operates at at least one 10 Megabits per second (Mbps), 100 Mbps and/or 1000 Mbps.

20. A system comprising:

a physical layer device that is adapted to communicate with a cable medium and that includes;

comprising;

first input/output means for communicating with the cable medium;

first transceiver means for communicating with said first input/output terminal and the cable medium; and

cable testing means for testing the cable medium and for determining a cable status; and

indicating means, that communicates with said physical layer device, for indicating at least one of link presence, link absence, link activity, link duplex and/or link speed during normal operation,

wherein said cable testing means also uses the indicating means to indicate at least one of cable testing status during said test and/or said cable status after said test.

21. The system of claim 20 wherein said cable testing means includes pretest means for sensing activity on the cable medium and enabling testing if activity is not detected for a first period, and test means that is enabled by said pretest module, for transmitting a test pulse on the cable medium, for measuring a reflection amplitude and calculates a cable length, wherein said cable testing means determines said status based on said measured amplitude and said calculated cable length.

22. The system of claim 21 wherein said pretest means enables testing if, during said first period, activity is detected and is subsequently not detected for a second period after said activity is detected.

23. The system of claim 21 further comprising converting means for measuring said reflection amplitude, wherein said test means measures offset at said converting means, subtracts said offset from said reflection amplitude, and zeroes said reflection amplitude below a floor, wherein said floor has a first value during a first period after said test pulse and a second value during a second period after said first period.

24. The system of claim 20 further comprising lookup means for storing a plurality of sets of reflection amplitudes as a function of cable length, wherein said cable testing means determines said cable status using said lookup means, said reflection amplitude and said cable length.

25. The system of claim 24 wherein said sets of reflection amplitudes define a plurality of windows including a first window that is defined by first and second thresholds, wherein said first threshold is based on a first set of reflection amplitudes that are measured as a function of cable length when a test cable type is an open circuit, and wherein said second threshold is based on a second set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a first impedance having a first impedance value.

26. The system of claim 25 wherein a second window is defined by third and fourth thresholds, wherein said third threshold is based on a third set of reflection amplitudes that are measured as a function of cable length when said test cable type is a short circuit, wherein said fourth threshold is based on a fourth set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a second impedance having a second impedance value.

27. The system of claim 26 wherein a third window is defined between said second and fourth thresholds.

28. The system of claim 27 wherein the cable medium is declared an open circuit when said reflection amplitude is in said first window for said cable length and wherein the cable medium is declared a short circuit when said reflection amplitude is in said second window for said cable length, and wherein the cable medium is declared normal when said reflection amplitude is in said third window for said cable length.

29. The system of claim 20 wherein said cable status includes good, open and short cable statuses.

30. The system of claim 20 wherein said physical layer device includes a plurality of said input/output means and said cable testing means includes test actuating means for triggering said test during operation of said physical layer device for linked input/output means but not linked input/output means.

31. The system of claim 20 wherein said cable testing means enters a test fail status when the cable medium is active for a period greater than a test fail period.

32. The system of claim 20 wherein said cable testing means is integrated with said transceiver means in a single integrated circuit.

33. The system of claim 20 wherein the indicator includes at least one of an audio indicator and/or a visual indicator.

34. The system of claim 20 wherein the indicator includes at least one of a speaker, a light emitting diode (LED), and/or an incandescent light.

35. The system of claim 20 further comprising:

detecting means for detecting a power over Ethernet (POE) device;

power supply means for supplying power to the POE device; and

switching means for selectively providing power from said power supply means over the cable medium when said detecting means detects said POE device, wherein said cable testing means delays testing of the cable medium when said detecting means detects said POE device until said switching means provides said power.

36. The system of claim 20 wherein said physical layer device forms part of one of a switch, a router, a computer, a laptop, a smart videocassette recorder, an IP telephone, a fax machine, a modem, a television, a stereo, or a hand-held device.

37. The system of claim 20 wherein said physical layer device is implemented in an Ethernet network device.

38. The system of claim 37 wherein said Ethernet network device operates at at least one 10 Megabits per second (Mbps), 100 Mbps and/or 1000 Mbps.

39. A method of operating a physical layer device that is adapted to communicate with a cable medium comprising:

using an indicator to identify at least one of link presence, link absence, link activity, link duplex and/or link speed of said first input/output terminal during normal operation;

testing the cable medium using a cable tester that is associated with the physical layer device;

determining a cable status; and

using the indicator to indicate at least one of cable testing status during said test and/or said cable status after said test.

40. The method of claim 39 further comprising:

sensing activity on said cable medium;

enabling testing if said activity is not detected for a first period;

transmitting a test pulse on said cable medium;

measuring a reflection amplitude;

calculating a cable length; and

determining said cable status based on said measured amplitude and said calculated cable length.

41. The method of claim 40 wherein said enabling step enables testing if, during said first period, activity is detected and is subsequently not detected for a second period after said activity is detected.

42. The method of claim 39 further comprising:

using a lookup table that includes a plurality of sets of reflection amplitudes as a function of cable length; and

determining said status using said lookup table, said reflection amplitude and said cable length.

43. The method of claim 42 wherein said sets of reflection amplitudes define a plurality of windows including a first window that is defined by first and second thresholds, wherein said first threshold is based on a first set of reflection amplitudes that are measured as a function of cable length when a test cable type is an open circuit, and wherein said second threshold is based on a second set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a first impedance having a first impedance value.

44. The method of claim 43 wherein a second window is defined by third and fourth thresholds, wherein said third threshold is based on a third set of reflection amplitudes that are measured as a function of cable length when said test cable type is a short circuit, wherein said fourth threshold is based on a fourth set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a second impedance having a second impedance value.

45. The method of claim 44 wherein a third window is defined between said second and fourth thresholds.

46. The method of claim 45 further comprising:

declaring said cable medium an open circuit when said reflection amplitude is within said first window for said cable length;

declaring said cable medium a short circuit when said reflection amplitude is within said second window for said cable length; and

declaring said cable medium normal when said reflection amplitude is within said third window for said cable length.

47. The method of claim 39 wherein said status includes good, open and short statuses.

48. The method of claim 39 further comprising:

transmitting said test pulse when a common wire is used to transmit and receive;

measuring offset;

subtracting said offset from said reflection amplitude; and

detecting peaks, wherein if a second peak is not detected after a first peak and said reflection amplitude of said first peak is greater than a first threshold, a second test pulse having a second amplitude that is less than a first amplitude of said first test pulse is transmitted and wherein said second amplitude is one-half of said first amplitude.

49. The method of claim 48 further comprising:

declaring a close open status if said reflection amplitude of a first peak after transmitting said second test pulse is greater than a second threshold; and

declaring an open status if said first peak is detected after a predetermined period after transmitting said second test pulse.

50. The method of claim 49 further comprising:

declaring a perfectly terminated status if said first peak is not detected within said predetermined period after transmitting said second test pulse.

51. The method of claim 48 further comprising canceling said test pulse when said cable medium transmits and receives on a common wire.

52. The method of claim 48 further comprising:

measuring said reflection amplitude;

measuring offset;

subtracting said offset from said reflection amplitude; and

setting said reflection amplitude below a floor equal to zero.

53. The method of claim 52 wherein said floor has a first value during a first period after said test pulse and a second value during a second period after said first period.

54. The method of claim 39 further comprising:

generating a test fail status when said cable medium is active for a period greater than a test fail period.

55. The method of claim 39 further comprising implementing a cable tester and a transceiver in a single integrated circuit.

56. The method of claim 39 wherein the indicator includes at least one of an audio indicator and/or a visual indicator.

57. The method of claim 39 wherein the indicator includes at least one of a speaker, a light emitting diode (LED), and/or an incandescent light.

58. The method of claim 39 further comprising:

detecting a power over Ethernet (POE) device before performing said cable test.

59. The method of claim 58 further comprising:

selectively providing power over the cable medium when said detector detects said POE device; and

delaying testing of the cable medium when said POE device is detected until power is provided over the cable medium.

60. The method of claim 39 wherein said physical layer device is implemented in an Ethernet network device.

61. The method of claim 60 wherein said Ethernet network device operates at at least one 10 Megabits per second (Mbps), 100 Mbps and/or 1000 Mbps.

62. A physical layer device that is adapted to communicate with a cable medium and an indicator, comprising:

a first input/output terminal;

a first transceiver that communicates with said first input/output terminal and the cable medium;

a cable tester that tests the cable medium and determines a cable status; and

an indicator output circuit that communicates with said cable tester, that has first and second modes, that generates output signals for the indicator during said first mode that indicate at least one of said cable testing status during said test and/or said cable status after said test, and that generates said output signals for the indicator during said second mode that indicate at least one of link presence, link absence, link activity, link duplex and link speed of said first input/output terminal.

63. The physical layer device of claim 62 wherein said cable tester includes a pretest module that senses activity on the cable medium and enables testing if activity is not detected for a first period, and a test module that is enabled by said pretest module, transmits a test pulse on the cable medium, measures a reflection amplitude and calculates a cable length, wherein said cable tester determines said status based on said measured amplitude and said calculated cable length.

64. The physical layer device of claim 63 wherein said pretest module enables testing if, during said first period, activity is detected and is subsequently not detected for a second period after said activity is detected.

65. The physical layer device of claim 63 further comprising an analog to digital converter (ADC) that measures said reflection amplitude, wherein said test module measures offset at said ADC, subtracts said offset from said reflection amplitude, and zeroes said reflection amplitude below a floor, wherein said floor has a first value during a first period after said test pulse and a second value during a second period after said first period.

66. The physical layer device of claim 62 further comprising a lookup table that includes a plurality of sets of reflection amplitudes as a function of cable length, wherein said cable tester determines said cable status using said lookup table, said reflection amplitude and said cable length.

67. The physical layer device of claim 66 wherein said sets of reflection amplitudes define a plurality of windows including a first window that is defined by first and second thresholds, wherein said first threshold is based on a first set of reflection amplitudes that are measured as a function of cable length when a test cable type is an open circuit, and wherein said second threshold is based on a second set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a first impedance having a first impedance value.

68. The physical layer device of claim 67 wherein a second window is defined by third and fourth thresholds, wherein said third threshold is based on a third set of reflection amplitudes that are measured as a function of cable length when said test cable type is a short circuit, wherein said fourth threshold is based on a fourth set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a second impedance having a second Impedance value.

69. The physical layer device of claim 68 wherein a third window is defined between said second and fourth thresholds.

70. The physical layer device of claim 69 wherein the cable medium is declared an open circuit when said reflection amplitude is in said first window for said cable length and wherein the cable medium is declared a short circuit when said reflection amplitude is in said second window for said cable length, and wherein the cable medium is declared normal when said reflection amplitude is in said third window for said cable length.

71. The physical layer device of claim 62 wherein said cable status includes good, open and short cable statuses.

72. The physical layer device of claim 62 wherein said physical layer device includes a plurality of input/output terminals and said cable tester includes a test actuator that triggers said test during operation of said physical layer device for unlinked input/output terminals but not linked input/output terminals.

73. The physical layer device of claim 62 wherein said cable tester enters a test fail status when the cable medium is active for a period greater than a test fail period.

74. The physical layer device of claim 62 wherein said cable tester is integrated with said transceiver in a single integrated circuit.

75. A system comprising the physical layer device of claim 62 and further comprising said indicator wherein said indicator includes at least one of an audio indicator and a visual indicator.

76. A system comprising the physical layer device of claim 62 and further comprising said indicator, wherein said indicator includes at least one of a speaker, a light emitting diode (LED), and/or an incandescent light.

77. The physical layer device of claim 62 wherein said physical layer device forms part of one of a switch, a router, a computer, a laptop, a smart videocassette recorder, an IP telephone, a fax machine, a modem, a television, a stereo, and/or a hand-held device.

78. The physical layer device of claim 62 wherein said physical layer device is implemented in an Ethernet network device.

79. The physical layer device of claim 78 wherein said Ethernet network device operates at at least one 10 Megabits per second (Mbps), 100 Mbps and/or 1000 Mbps.

80. The physical layer device of claim 62 wherein said output signals include signals that alter at least one of an on/off state and/or a color of the indicator.

81. A system comprising the physical layer device of claim 62 and further comprising said indicator, wherein said indicator includes an array of light emitting diodes.

82. A physical layer device that is adapted to communicate with a cable medium and an indicator, comprising:

first input/output means for communicating with the cable medium;

first transceiver means for communicating with said first input/output means and the cable medium;

cable testing means for communicating for testing the cable medium and for determining a cable status; and

indicator output means that communicates with said cable testing means, that has first and second modes, for generating first output signals for the indicator during said first mode that indicate at least one of said cable testing status during said test and/or said cable status after said test, and for generating second output signals for the indicator during said second mode that indicate at least one of link presence, link absence, link activity, link duplex and/or link speed of said first input/output terminal.

83. The physical layer device of claim 82 wherein said cable testing means includes pretest means for sensing activity on the cable medium and enabling testing if activity is not detected for a first period, and test means that is enabled by said pretest module, for transmitting a test pulse on the cable medium, for measuring a reflection amplitude and calculates a cable length, wherein said cable testing means determines said status based on said measured amplitude and said calculated cable length.

84. The physical layer device of claim 83 wherein said pretest means enables testing if, during said first period, activity is detected and is subsequently not detected for a second period after said activity is detected.

85. The physical layer device of claim 83 further comprising converting means for measuring said reflection amplitude, wherein said test means measures offset at said converting means, subtracts said offset from said reflection amplitude, and zeroes said reflection amplitude below a floor, wherein said floor has a first value during a first period after said test pulse and a second value during a second period after said first period.

86. The physical layer device of claim 82 further comprising lookup means for storing a plurality of sets of reflection amplitudes as a function of cable length, wherein said cable testing means determines said cable status using said lookup means, said reflection amplitude and said cable length.

87. The physical layer device of claim 86 wherein said sets of reflection amplitudes define a plurality of windows including a first window that is defined by first and second thresholds, wherein said first threshold is based on a first set of reflection amplitudes that are measured as a function of cable length when a test cable type is an open circuit, and wherein said second threshold is based on a second set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a first impedance having a first impedance value.

88. The physical layer device of claim 87 wherein a second window is defined by third and fourth thresholds, wherein said third threshold is based on a third set of reflection amplitudes that are measured as a function of cable length when said test cable type is a short circuit, wherein said fourth threshold is based on a fourth set of reflection amplitudes that are measured as a function of cable length when said test cable type is terminated using a second impedance having a second impedance value.

89. The physical layer device of claim 88 wherein a third window is defined between said second and fourth thresholds.

90. The physical layer device of claim 89 wherein the cable medium is declared an open circuit when said reflection amplitude is in said first window for said cable length and wherein the cable medium is declared a short circuit when said reflection amplitude is in said second window for said cable length, and wherein the cable medium is declared normal when said reflection amplitude is in said third window for said cable length.

91. The physical layer device of claim 82 wherein said cable status includes good, open and short cable statuses.

92. The physical layer device of claim 82 wherein said physical layer device includes a plurality of said input/output means and said cable testing means includes test actuating means for triggering said test during operation of said physical layer device for linked input/output means but not linked input/output means.

93. The physical layer device of claim 82 wherein said cable testing means enters a test fail status when the cable medium is active for a period greater than a test fail period.

94. The physical layer device of claim 82 wherein said cable testing means is integrated with said transceiver means in a single integrated circuit.

95. A system comprising the physical layer device of claim 82 and further comprising said indicator, wherein said indicator includes at least one of an audio indicator and/or a visual indicator.

96. A system comprising the physical layer device of claim 82 and further comprising said indicator, wherein said indicator includes at least one of a speaker, a light emitting diode (LED), and/or an incandescent light.

97. The physical layer device of claim 82 further comprising:

detecting means for detecting a power over Ethernet (POE) device;

power supply means for supplying power to the POE device; and

switching means for selectively providing power from said power supply means over the cable medium when said detecting means detects said POE device, wherein said cable testing means delays testing of the cable medium when said detecting means detects said POE device until said switching means provides said power.

98. The physical layer device of claim 82 wherein said physical layer device forms part of one of a switch, a router, a computer, a laptop, a smart videocassette recorder, an IP telephone, a fax machine, a modem, a television, a stereo, or a hand-held device.

99. The physical layer device of claim 82 wherein said physical layer device is implemented in an Ethernet network device.

100. The physical layer device of claim 99 wherein said Ethernet network device operates at at least one 10 Megabits per second (Mbps), 100 Mbps and/or 1000 Mbps.

101. The physical layer device of claim 82 wherein said first and second output signals include signals that alter at least one of an on/off state and/or a color of the indicator.

102. A system comprising the physical layer device of claim 82 and further comprising said indicator, wherein said indicator includes an array of light emitting diodes.