Low power universal serial bus

1. A universal serial bus port comprising:

link layer circuitry and protocol layer circuitry that are compatible with a standard Universal Serial Bus 2.0 (USB2) protocol, the link layer circuitry and protocol layer circuitry to control a physical layer for transmitting and receiving data on a pair of signal lines; and

wherein the physical layer comprises a fully-digital Low-Speed/Full-Speed (LS/FS) transceiver to transmit and receive data on the pair of signal lines using single-ended signaling and, due to a lack of a pull-up device, the physical layer power consumption during the LS/FS idle state is eliminated except power consumption resulting from leakage current;

wherein the universal serial bus port is to detect device presence by receiving a digital ping from a device.

2. The universal serial port interface of claim 1 , wherein the fully-digital LS/FS transceiver comprises digital CMOS components configured for 1.0 Volt signaling.

3. The universal serial bus port of claim 1 , wherein the physical layer comprises a high speed (HS) transceiver configured to transmit and receive data on the pair of signal lines using differential signaling.

4. The universal serial bus port of claim 1 , wherein the HS transceiver is to use 0.2 Volt differential signaling.

5. The universal serial bus port of claim 1 , wherein the physical layer is configured to use single-ended signaling while operating in a FS/LS mode and is configured to use differential signaling while operating in a HS mode.

6. The universal serial bus port of claim 4 , wherein the universal serial bus port includes a repeater to convert signals received from the physical layer into USB2 compatible signals.

7. The universal serial bus port of claim 1 , wherein device disconnect is detected if the universal serial bus port does not receive the digital ping from the device within a specified time period.

8. A method of operating a Universal Serial Bus 2.0 (USB2) host, comprising:

detecting presence of a device coupled to the universal serial bus host by receiving a digital ping from the device;

determining the data rate capabilities of the device;

if the device is Low-Speed (LS) or Full-Speed (FS) capable, sending data to the device using digital, single-ended signaling on a pair of signal lines between the universal serial bus host and the device; and

after sending the data, entering an LS/FS idle mode by holding the pair of signal lines to ground at the host, wherein, due to a lack of a pull-up device, power consumption during the LS/FS idle state is eliminated except power consumption resulting from leakage current.

9. The method of claim 8 , comprising using 1.0 Volt digital signaling for LS and FS operation.

10. The method of claim 8 , comprising, if the device is High-Speed (HS) capable, sending data to the device using differential signaling on the pair of signal lines.

11. The method of claim 10 , using 0.2 Volt differential signaling for HS operation.

12. The method of claim 8 , comprising using single-ended signaling while operating in a FS/LS mode and using differential signaling while operating in a HS mode.

13. The method of claim 8 , comprising converting signals received from the universal serial bus host into USB2 compatible signals to be sent to the device.

14. The method of claim 8 , comprising detecting device disconnect if the universal serial bus port host does not receive the digital ping from the device within a specified time period.

15. A computing device comprising:

a universal serial bus host comprising:

a link layer circuitry and protocol layer circuitry that are compatible with a standard Universal Serial Bus 2.0 (USB2) protocol, the link layer circuitry and protocol layer circuitry to control a physical layer for transmitting and receiving data on a pair of signal lines to communicate with a device; and

wherein the physical layer comprises a digital Low-Speed/Full-Speed (LS/FS) transceiver without a current source or an operational amplifier, the LS/FS transceiver to transmit and receive data on the pair of signal lines using single-ended signaling, and wherein, due to a lack of a pull-up device, the physical layer power consumption during the LS/FS idle state is eliminated;

wherein the device coupled to the universal serial bus port is to indicate device presence by transmitting a digital ping to the universal serial bus host.

16. The computing device of claim 15 , wherein the fully-digital LS/FS transceiver comprises digital CMOS components configured for 1.0 Volt signaling and no analog components.

17. The computing device of claim 15 , wherein the physical layer comprises a high speed (HS) transceiver configured to transmit and receive data on the pair of signal lines using 0.2 Volt differential signaling.

18. The computing device of claim 15 , wherein device disconnect is detected if the universal serial bus host does not receive the digital ping from the device within a specified time period.