System and method for selectively placing portions of a physical layer into low power mode

1. A system to manage power, comprising:

a port to transmit and receive data;

a Media Access Control (MAC) layer;

a physical layer (PHY) coupled to the port;

a queue manager including a plurality of transmit queues and configured to send a queue depth signal to the idle port monitor that indicates whether one or more of the transmit queues have data for transmission; and

an idle port monitor, coupled to the port and the PHY, and configured to monitor the queue depth signal once every pre-determined period of time, determine whether the one or more transmit queues are empty for a pre-determined number of times based on the queue depth signal, receive a signal from the Media Access Control (MAC) layer, and generate a transition state signal based on the queue depth signal and the signal received from the MAC layer to selectively cause portions of a Physical Medium Attachment (PMA) layer and a Physical Medium Dependent (PMD) layer of the PHY to operate in a low power mode.

2. The system of claim 1 , wherein the port is active if the port is transmitting or receiving data.

3. The system of claim 1 , wherein the idle port monitor is configured to determine that the port is active if the queue depth signal indicates that a queue has data for transmission and to determine that the port is inactive if the queue depth signal indicates that no queue has data for transmission.

4. The system of claim 1 , wherein the idle port monitor is configured to wait a second pre-determined period of time and monitor a receive valid signal from the MAC layer and the queue depth signal every third pre-determined period of time and send the transition state signal to the PHY to operate the PHY in a normal mode if the receive valid signal indicates receipt of data via the port or the queue depth signal indicates that one or more transmit queues has data to transmit.

5. The system of claim 1 , further comprising:

a traffic shaper configured to de-queue data from transmit queues if the transition state signal indicates a normal power mode and to stop de-queuing data from the transmit queues if the transition state signal indicates the low power mode.

6. The system of claim 1 , wherein the idle port monitor is implemented in a layer of a communication stack that is higher than the PHY layer.

7. The system of claim 1 , wherein the MAC layer includes:

a receive MAC unit configured to send a receive valid signal to the idle port monitor to indicate receipt of data via the port from a link partner; and

a statistical unit configured to send transmit and receive statistics to the idle port monitor, wherein the transmit statistics are a number of packets transmitted via the port and the receive statistics are a number of packets received via the port;

wherein the idle port monitor is configured to selectively place portions of the PHY into the low power mode or a normal mode based on the receive valid signal, the transmit and receive statistics, and the queue depth signal that indicates whether data is present in transmit queues for transmission.

8. The system of claim 1 , wherein in the low power mode, analog and digital portions of the PHY that transmit or receive an idle signal from the link partner are operated in a normal power mode and other analog and digital portions of the PHY are operated in the low power mode.

9. The system of claim 1 , wherein the system conforms to the IEEE 802.3ab protocol.

10. A method to manage power, comprising:

monitoring a transmit data queue every pre-determined period of time;

determining whether the transmit data queue is empty for a pre-determined number of times within the pre-determined period of time;

receiving a signal from a Media Access Control (MAC) layer;

generating a transition state signal to stop de-queuing of data from the transmit queue based on the signal received from the MAC layer and when the transmit data queue is empty for the pre-determined number of times; and

selectively operating portions of a Physical Medium Attachment (PMA) layer and a Physical Medium Dependent (PMD) layer of a Physical Layer (PHY) that are used for functions other than transmitting and receiving an idle signal in a low power mode, based on the generating of the transition state signal.

11. The method of claim 10 , further comprising: operating portions of the PHY layer in low power mode if no data is being received via a port.

12. The method of claim 10 , after the selectively operating step, further comprising: monitoring the transmit queue once every second pre-determined period of time to determine whether the transmit queue has data for transmission.

13. The method of claim 10 , further comprising: monitoring a receive valid signal once every second pre-determined period of time to determine whether data is being received via a port.

14. The method of claim 13 , further comprising: generating the transition state signal to cause the portions of the PHY layer operating in the low power mode to operate in a normal power mode if the transmit queue has data for transmission or if the receive valid signal indicates that data is being received via the port.

15. The system of claim 1 , wherein the idle port monitor is configured to operate a Physical Coding Sublayer (PCS) layer of the PHY in a normal power mode based on the transition state signal.

16. The method of claim 10 , further comprising operating a Physical Coding Sublayer (PCS) layer of the PHY in a normal power mode based on the transition state signal.

17. A system to manage power, comprising:

a memory;

a queue manager including a plurality of transmit queues and configured to send a queue depth signal to an idle port monitor that indicates whether one or more of the transmit queues have data for transmission; and

a processor coupled to the memory and based on instructions stored in the memory, the processor configured to:

monitor the queue depth signal once every pre-determined period of time:

determine whether the one or more transmit queues are empty for a pre-determined number of times based on the queue depth signal;

receive a signal from a Media Access Control (MAC) layer; and

generate a transition state signal based on the queue depth signal and the signal received from the MAC layer to selectively operate portions of a Physical Medium Attachment (PMA) layer and a Physical Medium Dependent (PMD) layer of a physical layer (PHY) in a low power mode and to operate a Physical Coding Sublayer (PCS) layer of the PHY in a normal power mode.