Three phase and polarity encoded serial interface

• US 9,083,598 B2
• Filed: 03/14/2013
• Issued: 07/14/2015
• Est. Priority Date: 03/02/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wiley, George Alan
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Perez, James M
• Application Number:
  US13/826,546
• Publication Number:
  US 20130215991A1
• Time in Patent Office: 852 Days
• Field of Search: 341/50, 341/58, 341 68- 70, 375259-264, 375284-288, 375290-293
• US Class Current: 1/1
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/0282 Provision for current-mode coupling
• CPC Class Codes: H04L 25/0294 Provision for current-mode coupling
• CPC Class Codes: H04L 25/0298 Arrangement for terminating transmission lines
• CPC Class Codes: H04L 25/4917 using multilevel codes
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 5/20 using different combinations of lines, e.g. phantom working
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop

Abstract

A high speed serial interface is provided. In one aspect, the high speed serial interface uses three phase modulation for jointly encoding data and clock information. Accordingly, the need for de-skewing circuitry at the receiving end of the interface is eliminated, resulting in reduced link start-up time and improved link efficiency and power consumption. In one embodiment, the high speed serial interface uses fewer signal conductors than conventional systems having separate conductors for data and clock information. In another embodiment, the serial interface allows for data to be transmitted at any speed without the receiving end having prior knowledge of the transmission data rate. In another aspect, the high speed serial interface uses polarity encoded three phase modulation for jointly encoding data and clock information. This further increases the link capacity of the serial interface by allowing for more than one bit to be transmitted in any single baud interval.

Claims

1. A method for encoding data, comprising:

transmitting a three-phase signal on each of three conductors of a communication link, wherein the three-phase signal transmitted on each of the three conductors is in a different phase than the three-phase signals transmitted on the other conductors, and wherein transmitting the three-phase signal on the three conductors includes;

during a first of two sequential time intervals in a plurality of sequential time intervals,

disallowing a current flow in a first conductor of the three conductors while causing a current to flow between a second conductor of the three conductors and a third conductor of the three conductors; and

during a second of the two sequential time intervals,

disallowing a current flow in the second conductor while causing a current to flow between the first conductor and the third conductor when data to be encoded at a transition between the two sequential time intervals has a first value, and

disallowing a current flow in the third conductor while causing a current to flow between the first conductor and the second conductor when the data to be encoded at the transition between the two sequential time intervals has a second value,

wherein N encoding states are defined for the communications link, including at least three encoding states defined by flow of current in the three conductors,

wherein a change of encoding state to one of N−

1 available encoding states occurs at each transition between sequential time intervals, and

wherein N is an integer greater than or equal to six.

2. The method of claim 1, wherein the second conductor is open-circuited when a first bit of the data to be encoded at the transition between the two sequential time intervals is in a first binary state, and the third conductor is open-circuited when the first bit of the data is in a second binary state different from the first binary state.

3. The method of claim 2, wherein the current flows are caused by applying a first voltage level to one conductor and a second voltage level to another conductor, the first voltage level having a different polarity from the second voltage level.

4. The method of claim 3, further comprising:

encoding a second bit of the data to be encoded in a selection of polarities for the first voltage level and the second voltage level at the transition between the two sequential time intervals based on the data to be encoded.

5. The method of claim 4, wherein the polarities of the first voltage level and the second voltage level are selected based on the binary state of the second bit of the data to be encoded.

6. The method of claim 2, wherein two bits of data are encoded at each transition between the plurality of sequential time intervals.

7. The method of claim 1, wherein one bit of data is encoded at each transition between sequential pairs of the plurality of sequential time intervals.

8. The method of claim 1, wherein during the second of the two sequential time intervals, transmitting the three-phase signal further includes:

disallowing a current flow in the first conductor; and

reversing a direction of current flow between the second conductor and the third conductor when the data to be encoded at a transition between the two sequential time intervals has a third value.

9. The method of claim 8, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

10. The method of claim 1, wherein:

current flow is disallowed in one of the first conductor, the second conductor, and the third conductor during each of the plurality of sequential time intervals,

a voltage differential is provided to the other two of the first conductor, the second conductor, and the third conductor, and

the voltage differential has a polarity that is one of a positive polarity or a negative polarity, thereby providing six signaling states using three conductors.

11. The method of claim 10, wherein a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, and two bits of data are encoded at the each transition.

12. The method of claim 10, wherein at least one of a change of polarity of the voltage differential and a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, thereby providing 5 possible state changes at the each transition.

13. The method of claim 12, wherein log₂(5) bits are encoded per transition between sequential ones of the plurality of sequential time intervals.

14. The method of claim 12, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

15. The method of claim 1, wherein the three-phase signal transmitted in each of the plurality of sequential time intervals comprises one of two three-phase signals that have different phase rotation directions.

16. The method of claim 1, wherein transmitting the three-phase signal includes transmitting a different phase of the three-phase signal on each of the first conductor, the second conductor, and the third conductor.

17. The method of claim 1, wherein transmitting the three-phase signal includes transmitting a phase-shifted version of the three-phase signal on each of three conductors with a phase of 120°

between each pair of the three conductors.

18. An apparatus for encoding data, comprising:

means for transmitting a three-phase signal on each of at least three conductors, wherein the three-phase signal transmitted on each of the three conductors is in a different phase than the three-phase signals transmitted on the other conductors; and

means for driving each of the at least three conductors responsive to the means for transmitting the three-phase signal, wherein;

during a first of two sequential time intervals in a plurality of sequential time intervals, the means for driving;

disallows a current flow in a first conductor of the at least three conductors; and

causes a current to flow between a second conductor of the at least three conductors and a third conductor of the at least three conductors; and

during a second of the two sequential time intervals the means for driving;

disallows a current flow in the second conductor and causes the current to flow between the first conductor and the third conductor when data to be encoded at a transition between the two sequential time intervals has a first value; and

disallows a current flow in the third conductor and causes the current to flow between the first conductor and the second conductor when the data to be encoded at the transition between the two sequential time intervals has a second value,

wherein N encoding states are defined for the communications link, including at least three encoding states defined by flow of current in the three conductors,

wherein a change of encoding state to one of N−

1 available encoding states occurs at each transition between sequential time intervals, and

wherein N is an integer greater than or equal to six.

19. The apparatus of claim 18, wherein the second conductor is open-circuited when a first bit of the data to be encoded at the transition between the two sequential time intervals is in a first binary state, and the third conductor is open-circuited when the first bit of the data is in a second binary state different from the first binary state.

20. The apparatus of claim 19, wherein the current flows are caused by applying a first voltage level to one conductor and a second voltage level to another conductor, the first voltage level having a different polarity from the second voltage level.

21. The apparatus of claim 20, further comprising:

means for encoding a second bit of the data to be encoded in a selection of polarities for the first voltage level and the second voltage level at the transition between the two sequential time intervals based on the data to be encoded.

22. The apparatus of claim 21, wherein the polarities of the first voltage level and the second voltage level are selected based on the binary state of the second bit of the data to be encoded.

23. The apparatus of claim 19, wherein two bits of data are encoded at each transition between the plurality of sequential time intervals.

24. The apparatus of claim 18, wherein one bit of data is encoded at each transition between sequential pairs of the plurality of sequential time intervals.

25. The apparatus of claim 18, wherein during the second of the two sequential time intervals, the means for driving disallows a current flow in the first conductor and reverses a direction of current flow between the second conductor and the third conductor when the data to be encoded at a transition between the two sequential time intervals has a third value.

26. The apparatus of claim 25, wherein the means for transmitting encodes 16 bits of data using less than 8 transitions between sequential time intervals.

27. The apparatus of claim 18, wherein:

current flow is disallowed in one of the first conductor, the second conductor, and the third conductor during each of the plurality of sequential time intervals,

a voltage differential is provided to the other two of the first conductor, the second conductor, and the third conductor, and

the voltage differential has a polarity that is one of a positive polarity or a negative polarity, thereby providing six signaling states using three conductors.

28. The apparatus of claim 27, wherein a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, and two bits of data are encoded at the each transition.

29. The apparatus of claim 27, wherein at least one of a change of polarity of the voltage differential and a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, thereby providing 5 possible state changes at the each transition.

30. The apparatus of claim 29, wherein log₂(5) bits are encoded per transition between sequential ones of the plurality of sequential time intervals.

31. The apparatus of claim 29, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

32. The apparatus of claim 18, wherein the three-phase signal transmitted in each of the plurality of sequential time intervals comprises one of two three-phase signals that have different phase rotation directions.

33. The apparatus of claim 18, wherein the means for transmitting the three-phase signal transmits a different phase of the three-phase signal on each of the first conductor, the second conductor, and the third conductor.

34. The apparatus of claim 18, wherein the means for transmitting the three-phase signal transmits the three-phase signal on three conductors with a phase shift of 120°

between each pair of the three conductors.

35. An apparatus that encodes data, comprising:

a processing system configured to;

transmit a three-phase signal on each of three conductors of a communication link, wherein the three-phase signal transmitted on each of the three conductors is in a different phase than the three-phase signals transmitted on the other conductors,

wherein during a first of two sequential time intervals in a plurality of sequential time intervals the processing system is configured to;

cause a current flow in a first conductor of the three conductors to be disallowed; and

cause a current to flow between a second conductor of the three conductors and a third conductor of the three conductors; and

wherein during a second of the two sequential time intervals, the processing system is configured to;

cause a current flow in the second conductor to be disallowed, and cause the current to flow between the first conductor and the third conductor when data to be encoded at a transition between the two sequential time intervals has a first value, and

cause a current flow in the third conductor to be disallowed, and cause the current to flow between the first conductor and the second conductor when the data to be encoded at the transition between the two sequential time intervals has a second value,

wherein N encoding states are defined for the communications link, including at least three encoding states defined by flow of current in the three conductors,

wherein a change of encoding state to one of N−

1 available encoding states occurs at each transition between sequential time intervals, and

wherein N is an integer greater than or equal to six.

36. The apparatus of claim 35, wherein the second conductor is open-circuited when a first bit of the data to be encoded at the transition between the two sequential time intervals is in a first binary state, and the third conductor is open-circuited when the first bit of the data is in a second binary state different from the first binary state.

37. The apparatus of claim 36, wherein current flows are caused by applying a first voltage level to one conductor and a second voltage level to another conductor, the first voltage level having a different polarity from the second voltage level.

38. The apparatus of claim 37, wherein the processing system is configured to:

encode a second bit of the data to be encoded in a selection of polarities for the first voltage level and the second voltage level at the transition between the two sequential time intervals based on the data to be encoded.

39. The apparatus of claim 38, wherein the polarities of the first voltage level and the second voltage level are selected based on the binary state of the second bit of the data to be encoded.

40. The apparatus of claim 36, wherein two bits of data are encoded at each transition between the plurality of sequential time intervals.

41. The apparatus of claim 35, wherein one bit of data is encoded at each transition between sequential pairs of the plurality of sequential time intervals.

42. The apparatus of claim 35, wherein during the second of the two sequential time intervals, the three-phase signal is transmitted by:

disallowing a current flow in the first conductor; and

reversing a direction of current flow between the second conductor and the third conductor when the data to be encoded at a transition between the two sequential time intervals has a third value.

43. The apparatus of claim 42, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

44. The apparatus of claim 35, wherein:

current flow is disallowed in one of the first conductor, the second conductor, and the third conductor during each of the plurality of sequential time intervals,

a voltage differential is provided to the other two of the first conductor, the second conductor, and the third conductor, and

the voltage differential has a polarity that is one of a positive polarity or a negative polarity, thereby providing six signaling states using three conductors.

45. The apparatus of claim 44, wherein a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, and two bits of data are encoded at the each transition.

46. The apparatus of claim 44, wherein at least one of a change of polarity of the voltage differential and a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, thereby providing 5 possible state changes at the each transition.

47. The apparatus of claim 46, wherein log₂(5) bits are encoded per transition between sequential ones of the plurality of sequential time intervals.

48. The apparatus of claim 46, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

49. The apparatus of claim 35, wherein the three-phase signal transmitted in each of the plurality of sequential time intervals comprises one of two three-phase signals that have different phase rotation directions.

50. The apparatus of claim 35, wherein a different phase of the three-phase signal is transmitted on each of the first conductor, the second conductor, and the third conductor.

51. The apparatus of claim 35, wherein the three-phase signal is transmitted on three conductors with a phase shift of 120°

between each pair of the three conductors.

52. A non-transitory machine-readable storage medium having instructions stored thereon for encoding data, which when executed by at least one processor causes the at least one processor to:

transmit a three-phase signal on each of three conductors of a communication link, wherein the three-phase signal transmitted on each of the three conductors is in a different phase than the three-phase signals transmitted on the other conductors, including code for;

disallowing a current flow in a first conductor of the three conductors, and causing a current to flow between a second conductor of the three conductors and a third conductor of the three conductors during a first of two sequential time intervals in a plurality of sequential time intervals; and

disallowing a current flow in the second conductor and causing a current to flow between the first conductor and the third conductor during a second of the two sequential time intervals when data to be encoded at a transition between the two sequential time intervals has a first value,

disallowing a current flow in the third conductor and causing a current to flow between the first conductor and the second conductor during the second of the two sequential time intervals when the data to be encoded at the transition between the two sequential time intervals has a second value,

wherein N encoding states are defined for the communications link, including at least three encoding states defined by flow of current in the three conductors,

wherein a change of encoding state to one of N−

1 available encoding states occurs at each transition between sequential time intervals, and

wherein N is an integer greater than or equal to six.

53. The machine-readable storage medium of claim 52, wherein the second conductor is open-circuited when a first bit of the data to be encoded at the transition between the two sequential time intervals is in a first binary state, and the third conductor is open-circuited when the first bit of the data is in a second binary state different from the first binary state.

54. The machine-readable storage medium of claim 53, wherein the current flows are caused by applying a first voltage level to one conductor and a second voltage level to another conductor, the first voltage level having a different polarity from the second voltage level.

55. The machine-readable storage medium of claim 54, wherein the storage medium comprises code for:

encoding a second bit of the data to be encoded in a selection of polarities for the first voltage level and the second voltage level at the transition between the two sequential time intervals based on the data to be encoded.

56. The machine-readable storage medium of claim 55, wherein the polarities of the first voltage level and the second voltage level are selected based on the binary state of the second bit of the data to be encoded.

57. The machine-readable storage medium of claim 53, wherein two bits of data are encoded at each transition between the plurality of sequential time intervals.

58. The machine-readable storage medium of claim 52, wherein one bit of data is encoded at each transition between sequential pairs of the plurality of sequential time intervals.

59. The machine-readable storage medium of claim 52, wherein the code for transmitting the three-phase signal includes code for:

disallowing a current flow in the first conductor; and

reversing a direction of current flow between the second conductor and the third conductor during the second of the two sequential time intervals when the data to be encoded at a transition between the two sequential time intervals has a third value.

60. The machine-readable storage medium of claim 59, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

61. The machine-readable storage medium of claim 52, wherein:

current flow is disallowed in one of the first conductor, the second conductor, and the third conductor during each of the plurality of sequential time intervals,

a voltage differential provided to the other two of the first conductor, the second conductor, and the third conductor, and

the voltage differential has a polarity that is one of a positive polarity or a negative polarity, thereby providing six signaling states using three conductors.

62. The machine-readable storage medium of claim 61, wherein a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, and two bits of data are encoded at the each transition.

63. The machine-readable storage medium of claim 61, wherein at least one of a change of polarity of the voltage differential and a change of conductor in which current flow is disallowed occurs at each transition between sequential time intervals, thereby providing 5 possible state changes at the each transition.

64. The machine-readable storage medium of claim 63, wherein log₂(5) bits are encoded per transition between sequential ones of the plurality of sequential time intervals.

65. The machine-readable storage medium of claim 63, wherein 16 bits of data are encoded using less than 8 transitions between sequential time intervals.

66. The machine-readable storage medium of claim 52, wherein the three-phase signal transmitted in each of the plurality of sequential time intervals comprises one of two three-phase signals that have different phase rotation directions.

67. The machine-readable storage medium of claim 52, wherein the code for transmitting the three-phase signal includes code for transmitting a different phase of the three-phase signal on each of the first conductor, the second conductor, and the third conductor.

68. The machine-readable storage medium of claim 52, wherein the code for transmitting the three-phase signal includes code for transmitting the three-phase signal on three conductors with a phase shift of 120°

between each pair of the three conductors.