Efficient electrical hibernate entry and recovery

1. A device for communication with a second device via differential signal lines, the device comprising:

a controller;

one or more first switches in communication with the controller and configured to connect, during at least a part of a power-save mode in response to receiving at least one signal indicative of the power-save mode from the controller, low-impedance to a first differential signal line and to maintain voltage on the first differential signal line to the second device to be less than complementary voltages used during signaling with the second device; and

one or more second switches in communication with the controller and configured to connect, during the at least a part of a power-save mode in response to receiving the at least one signal from the controller, low impedance to a second differential signal line and to maintain voltage on the second differential signal line to the second device to be less than complementary voltages used during signaling with the second device.

2. The device of claim 1 , wherein the voltages on the voltage maintained on the first differential signal line and the second differential signal line are substantially the same.

3. The device of claim 2 , further comprising:

a driver circuit configured to drive the complementary voltages on the differential signal lines, the driver circuit including a first amplifier and a second amplifier;

a first signaling switch configured to electrically connect the first amplifier with the first differential signal line; and

a second signaling switch configured to electrically connect the second amplifier with the second differential signal line,

wherein the controller is configured to:

close the one or more first switches and the one or more second switches, and open the first signaling switch and second signaling switch during the at least a part of the power-save mode; and

open the one or more first switches and the one or more second switches, and close the first signaling switch and second signaling switch during a signaling mode.

4. The device of claim 3 , wherein the one or more first switches are configured to electrically connect the first differential signal line to ground; and

wherein the one or more second switches are configured to electrically connect the second differential signal line to ground.

5. The device of claim 1 , wherein the one or more first switches are configured to connect the first differential signal line to ground in response to receiving the at least one signal; and

wherein the one or more second switches are configured to connect the second differential signal line to the ground in response to receiving the at least one signal.

6. A device configured to communicate via differential signal lines, the device comprising:

driver circuitry configured to drive complementary voltages on the differential signal lines to encode information on the differential signal lines;

circuitry in electrical communication with at least one of the differential signal lines, the circuitry configured to:

receive an instruction to configure the at least one of the differential signal lines to a power-save mode; and

in response to receiving the instruction, configuring the device so that the at least one of the differential signal lines is not driven from any driver circuitry during at least a part of the power-save mode.

7. The device of claim 6 , wherein the circuitry is configured to connect the at least one of the differential signal lines ground in response to receiving the instruction.

8. The device of claim 7 ,

wherein the circuitry is configured to connect both of the differential signal lines electrically to ground in response to receiving the instruction.

9. The device of claim 6 , wherein the voltages on both of the differential signal lines are substantially the same.

10. The device of claim 6 , wherein the driver circuitry is configured to send a differential wake-up signal to a peripheral device via the differential signal lines, the differential wake-up signal comprising a first wake-up voltage on the first differential signal line and a second wake-up voltage on the second differential signal line; and

wherein a difference between the first wake-up voltage and the second wake-up voltage is greater than a difference between the first predetermined low-voltage and the second predetermined low-voltage.

11. A method of configuring differential signal lines during at least a part of a power-save mode, the method comprising:

driving complementary voltages on the differential signal lines to encode a power-save command during a signaling mode;

connecting a first differential signal line to low-impedance and a first predetermined voltage during the at least a part of a power-save mode; and

connecting a second differential signal line to low-impedance and a second predetermined voltage during the at least a part of the power-save mode,

wherein the first predetermined voltage and the second predetermined voltage are less than the complementary voltages during the signaling mode.

12. The method of claim 11 , wherein the first predetermined voltage is substantially equal to the second predetermined voltage.

13. The method of claim 11 , wherein connecting the first differential signal line to low-impedance comprises electrically connecting the first differential signal line to ground; and

connecting the second differential signal line to low-impedance comprises electrically connecting the second differential signal line to the ground.

14. The method of claim 11 , further comprising sending a differential wake-up signal via the differential signal lines, the differential wake-up signal encoding a type of wake-up from a plurality of types of wake-up.

15. A device configured to communicate via differential signal lines with a second device, the device comprising:

a controller; and

circuitry in communication with the controller, the circuitry configured to:

receive, during at least a part of a power-save mode, predetermined low-impedance voltages on the differential signal lines to the second device, the predetermined low-impedance voltages being less than complementary voltages during a signaling mode with the second device;

determine whether a differential wake-up signal has been received; and

output a wake up signal to the controller in response to determining that the differential wake-up has been received.

16. A device configured to communicate via differential signal lines with a second device, the device comprising:

a controller; and

circuitry in communication with the controller, the circuitry configured to:

in a power-save mode, determine whether a differential wake-up signal has been received; and

output a wake up signal to the controller in response to determining that the differential wake-up has been received,

wherein the circuitry comprises an amplifier;

wherein the differential signal lines includes a first differential line and a second differential line;

wherein the differential wake-up signal comprises a first wake-up voltage on the first differential signal line and a second wake-up voltage on the second differential signal line; and

wherein the amplifier is configured to output the wake up signal only when a difference between the first wake-up voltage and the second wake-up voltage is greater than a predetermined amount.

17. A device configured to communicate via differential signal lines with a second device, the device comprising:

a controller; and

circuitry in communication with the controller, the circuitry configured to:

in a power-save mode, determine whether a differential wake-up signal has been received; and

output a wake up signal to the controller in response to determining that the differential wake-up has been received,

wake-up signal evaluator circuitry configured to determine a type of the differential wake-up signal, wherein the type of the differential wake-up signal determining actions of the device to wake up in response to receiving the differential wake-up signal.

18. The device of claim 17 , wherein a first type of differential wake-up signal comprises a boot wake-up, the device booting up in response to receiving the boot wake-up; and

wherein a second type of differential wake-up signal comprises a hibernation wake-up, the device powering up in response to receiving the hibernation wake-up.

19. The device of claim 15 , wherein resistance for the differential signal lines when determining whether the differential wake-up signal has been received is substantially the same as resistance for the differential signal lines when determining a differential signal on the differential line.

20. A method of operating a device during a power-save mode, the method comprising:

receiving, during a signaling mode, complementary voltages on the differential signal lines to encode a power-save command on the differential signal lines;

receiving, during at least a part of a power-save mode, low-impedance and predetermined voltages on the differential signal lines, the predetermined voltages being less than the complementary voltages during the signaling mode;

determining whether a differential wake-up signal has been received; and

outputting a wake up signal in response to determining that the differential wake-up has been received.

21. The method of claim 20 , wherein the predetermined voltages are substantially the same.

22. The method of claim 20 , wherein the predetermined voltages are substantially ground.

23. The method of claim 20 , further comprising:

determine a type of the differential wake-up signal, the type being one of a plurality of types; and

waking up in response to the determined type of differential wake-up signal.

24. The method of claim 23 , wherein a first type of differential wake-up signal comprises a boot wake-up; and

wherein waking up comprises booting up in response to receiving the boot wake-up.

25. A device for communication with a second device via differential signal lines, the device comprising:

a controller;

a driver circuit configured to drive complementary voltages on the differential signal lines, the driver circuit including a first amplifier and a second amplifier;

a first signaling switch configured to electrically connect the first amplifier with a first differential signal line; and

a second signaling switch configured to electrically connect the second amplifier with a second differential signal line,

wherein the controller is configured to:

operate the first signaling switch to disconnect the first amplifier from the first differential signal line during at least a part of the power-save mode; and

operate the second signaling switch to disconnect the second amplifier from the second differential signal line during at least a part of the power-save mode.

26. The device of claim 25 , further comprising:

one or more first switches configured to maintain voltage on the first differential signal line to be no greater than complementary voltages during signaling and disallow signaling on the first differential signal line during at least a part of a power-save mode in response to receiving at least one signal from the controller; and

one or more second switches configured to maintain voltage on the second differential signal line to be no greater than complementary voltages during signaling and disallow signaling on the second differential signal line during the at least a part of the power-save mode in response to receiving the at least one signal from the controller.

27. The device of claim 26 , wherein the controller is further configured to:

operate the first switch to disconnect the first differential signal line from ground during at least a part of a signaling mode;

operate the second switch to disconnect the second differential signal line from ground during at least a part of the signaling mode;

operate the first signaling switch to connect the first amplifier from the first differential signal line during at least a part of the signaling mode; and

operate the second signaling switch to connect the second amplifier from the second differential signal line during at least a part of the signaling mode.

28. A device for communication with a second device via differential signal lines, the device comprising:

a controller configured to send an instruction to configure at least one of the differential signal lines to a power-save mode; and

one or more switches configured to receive the instruction to configure the at least one of the differential signal lines to the power-save mode so that the at least one of the differential signal lines is substantially at ground during at least a part of the power-save mode.

29. The device of claim 28 , wherein the one more switches comprises:

at least a first switch configured to electrically connect a first differential signal line substantially to ground during the at least a part of the power-save mode in response to receiving the instruction from the controller; and

at least a second switch configured to electrically connect a second differential signal line substantially to ground during the at least a part of the power-save mode in response to receiving the instruction from the controller.

30. The device of claim 29 , wherein the first switch and the second switch constrain the voltages on the differential signal lines substantially to ground.

31. The device of claim 30 , further comprising:

a driver circuit configured to drive the complementary voltages on the differential signal lines, the driver circuit including a first amplifier and a second amplifier;

a first signaling switch configured to electrically connect the first amplifier with the first differential signal line; and

a second signaling switch configured to electrically connect the second amplifier with the second differential signal line,

wherein the controller is configured to:

operate the at least a first switch to connect the first differential signal line to ground during at least a part of the power-save mode;

operate the at least a second switch to connect the second differential signal line to ground during at least a part of the power-save mode;

operate the first signaling switch to disconnect the first amplifier from the first differential signal line during at least a part of the power-save mode; and

operate the second signaling switch to disconnect the second amplifier from the second differential signal line during at least a part of the power-save mode.

32. The device of claim 31 , wherein the controller is further configured to:

operate the at least a first switch to disconnect the first differential signal line from ground during at least a part of a signaling mode;

operate the at least a second switch to disconnect the second differential signal line from ground during at least a part of the signaling mode;

operate the first signaling switch to connect the first amplifier to the first differential signal line during at least a part of the signaling mode; and

operate the second signaling switch to connect the second amplifier to the second differential signal line during at least a part of the signaling mode.