VSC7511 datasheet(56/324 Pages) MICROSEMI

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Functional Descriptions

VMDS-10488 VSC7511 Datasheet Revision 4.2

for power-sensitive applications. It uses a signal detect function that monitors the media interface for the

presence of a link to determine when to automatically power-down the PHY. The PHY “wakes up” at a

programmable interval and attempts to wake-up the link partner PHY by sending a burst of FLP over

copper media.

The ActiPHY power management mode in the integrated transceivers is enabled on a per-port basis

during normal operation at any time by setting PHY_AUX_CTRL_STAT.ACTIPHY_ENA to 1.

Three operating states are possible when ActiPHY mode is enabled:

•

Low power state

•

LP wake-up state

•

Normal operating state (link up state)

The PHY switches between the low power state and the LP wake-up state at a programmable rate (the

default is two seconds) until signal energy is detected on the media interface pins. When signal energy is

detected, the PHY enters the normal operating state. If the PHY is in its normal operating state and the

link fails, the PHY returns to the low power state after the expiration of the link status time-out timer. After

reset, the PHY enters the low power state.

When auto-negotiation is enabled in the PHY, the ActiPHY state machine operates as described. If auto-

negotiation is disabled and the link is forced to use 10BT or 100BTX modes while the PHY is in its low

power state, the PHY continues to transition between the low power and LP wake-up states until signal

energy is detected on the media pins. At that time, the PHY transitions to the normal operating state and

stays in that state even when the link is dropped. If auto-negotiation is disabled while the PHY is in the

normal operation state, the PHY stays in that state when the link is dropped and does not transition back

to the low power state.

The following illustration shows the relationship between ActiPHY states and timers.

Figure 14 •

ActiPHY State Diagram

3.5.6.1

Low Power State

All major digital blocks are powered down in the lower power state.

In this state, the PHY monitors the media interface pins for signal energy. The PHY comes out of low

power state and transitions to the normal operating state when signal energy is detected on the media.

This happens when the PHY is connected to one of the following:

•

Auto-negotiation capable link partner

•

Another PHY in enhanced ActiPHY LP wake-up state

In the absence of signal energy on the media pins, the PHY transitions from the low power state to the

LP wake-up state periodically based on the programmable sleep timer

Low Power State

LP Wake-up

State

Normal

Operation State

Signal Energy Detected on

Media

Timeout Timer Expires and

Auto-negotiation Enabled

Sleep Timer Expires

FLP Burst or

Clause 37 Restart

Signal Sent

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