N-phase signal transition alignment
System, methods and apparatus are described that facilitate transmission of data, particularly between two devices within an electronic apparatus. Information is transmitted in N-phase polarity encoded symbols. Drivers may be adapted or configured to align state transitions on two or more connectors in order to minimize a transition period between consecutive symbols. The drivers may include circuits that advance or delay certain transitions. The drivers may include pre-emphasis circuits that operate to drive the state of a connector for a portion of the transition period, even when the connector is transitioned to an undriven state.
1. A method for data communications, comprising:
determining a transition in signaling state of three wires of a communication link between a pair of consecutive symbols transmitted on the communication link, wherein each symbol defines a different signaling state of the three wires of the communication link; and
selectively increasing driver strength prior to the transition in signaling state of the three wires when the transition in signaling state includes a change in signaling state of a corresponding wire on which a signal is transmitted,
wherein during transmission of a first symbol in the pair of consecutive symbols, a first wire of the three wires and a second wire of the three wires are at voltage levels that have different polarities from one another, and
wherein during transmission of a second symbol in the pair of consecutive symbols, the first wire and a third wire of the three wires are at the voltage levels that have different polarities from one another.
2. The method of claim 1 , wherein during transmission of the first symbol the third wire has a voltage that lies substantially halfway between voltage levels of the first wire and the second wire.
3. The method of claim 1 , wherein driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal.
4. The method of claim 1 , wherein driver strength is not increased when the change in signaling state of the corresponding wire does not include a polarity change of the signal.
5. The method of claim 1 , and further comprising:
initiating transmission of the second symbol on one wire before transmission of the first symbol is terminated.
6. The method of claim 1 , and further comprising:
initiating transmission of the second symbol on one wire after transmission of the first symbol is terminated.
7. The method of claim 1 , wherein driver strength is increased or not increased based on signaling state of all three wires after the transition.
8. The method of claim 7 , wherein driver strength is increased or not increased based on changes in relative signaling states of each pairing of wires in the three wires.
9. The method of claim 7 , wherein driver strength is increased or not increased based on changes in signaling state of all three wires.
10. The method of claim 7 , wherein increasing driver strength comprises:
adding pre-emphasis to one or more driver outputs based on prior knowledge of a type of transition in signaling state of the three wires of the communication link between the pair of consecutive symbols.
11. An apparatus, comprising:
means for determining a transition in signaling state of three wires of a communication link between a pair of consecutive symbols transmitted on the communication link, wherein each symbol defines a different signaling state of the three wires of the communication link; and
means for selectively increasing driver strength prior to the transition in signaling state of the three wires when the transition in signaling state includes a change in signaling state of a corresponding wire on which a signal is transmitted,
wherein during transmission of a first symbol in the pair of consecutive symbols, a first wire of the three wires and a second wire of the three wires are at voltage levels that have different polarities from one another, and
wherein during transmission of a second symbol in the pair of consecutive symbols, the first wire and a third wire of the three wires are at the voltage levels that have different polarities from one another.
12. The apparatus of claim 11 , wherein during transmission of the first symbol the third wire has a voltage that lies substantially halfway between voltage levels of the first wire and the second wire.
13. The apparatus of claim 11 , wherein driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal, and wherein driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal.
14. The apparatus of claim 11 , further comprising:
means for selectively initiating transmission of the second symbol on one wire before or after transmission of the first symbol is terminated.
15. The apparatus of claim 11 , wherein driver strength is increased or not increased based on signaling state of all three wires after the transition.
16. The apparatus of claim 11 , wherein driver strength is increased or not increased based on changes in relative signaling states of each pairing of wires in the three wires.
17. The apparatus of claim 16 , wherein driver strength is increased or not increased based on changes in signaling state of all three wires.
18. The apparatus of claim 16 , wherein the means for selectively increasing driver strength is configured to add pre-emphasis to one or more driver outputs based on prior knowledge of a type of transition in signaling state of the three wires of the communication link between the pair of consecutive symbols.
19. An apparatus, comprising:
a processing circuit configured to:
determine a transition in signaling state of three wires of a communication link between a pair of consecutive symbols transmitted on the communication link, wherein each symbol defines a different signaling state of the three wires of the communication link; and
selectively increase driver strength prior to the transition in signaling state of the three wires when the transition in signaling state includes a change in signaling state of a corresponding wire on which a signal is transmitted,
wherein during transmission of a first symbol in the pair of consecutive symbols, a first wire of the three wires and a second wire of the three wires are at voltage levels that have different polarities from one another, and
wherein during transmission of a second symbol in the pair of consecutive symbols, the first wire and a third wire of the three wires are at the voltage levels that have different polarities from one another.
20. The apparatus of claim 19 , wherein driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal, and wherein driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal.
21. The apparatus of claim 19 , wherein the processing circuit is configured to:
selectively initiate transmission of the second symbol on one wire before or after transmission of the first symbol is terminated.
22. The apparatus of claim 19 , wherein the processing circuit is configured to pre-emphasize the signal by initiating the transmission of the second symbol before the transmission of the first symbol is terminated.
23. The apparatus of claim 19 , wherein driver strength is increased or not increased based on changes in relative signaling states of each pairing of wires in the three wires.
24. The apparatus of claim 19 , wherein the processing circuit is configured to:
add pre-emphasis to one or more driver outputs based on prior knowledge of a type of transition in signaling state of the three wires of the communication link between the pair of consecutive symbols.
25. A non-transitory processor-readable storage medium having one or more instructions which, when executed by at least one processing circuit, cause the at least one processing circuit to:
determine a transition in signaling state of three wires of a communication link between a pair of consecutive symbols transmitted on the communication link, wherein each symbol defines a different signaling state of the three wires of the communication link; and
selectively increase driver strength prior to the transition in signaling state of the three wires when the transition in signaling state includes a change in signaling state of a corresponding wire on which a signal is transmitted,
wherein during transmission of a first symbol in the pair of consecutive symbols, a first wire of the three wires and a second wire of the three wires are at voltage levels that have different polarities from one another, and
wherein during transmission of a second symbol in the pair of consecutive symbols, the first wire and a third wire of the three wires are at the voltage levels that have different polarities from one another.
26. The non-transitory storage medium of claim 25 , wherein during transmission of the first symbol the third wire has a voltage that lies substantially halfway between voltage levels of the first wire and the second wire.
27. The non-transitory storage medium of claim 25 , driver strength is increased when the change in signaling state of the corresponding wire includes a polarity change of the signal.
28. The non-transitory storage medium of claim 25 , further comprising instructions that cause the at least one processing circuit to:
initiate transmission of the second symbol on one wire before the transmission of the first symbol is terminated.
29. The non-transitory storage medium of claim 25 , further comprising instructions that cause the at least one processing circuit to:
initiate transmission of the second symbol on one wire after the transmission of the first symbol is terminated.
30. The non-transitory storage medium of claim 25 , further comprising instructions that cause the at least one processing circuit to:
add pre-emphasis to one or more driver outputs based on prior knowledge of a type of transition in signaling state of the three wires of the communication link between the pair of consecutive symbols.