VSC8221 datasheet(47/138 Pages) MICROSEMI

47 / 138 page

VSC8221

Data Sheet

VMDS-10106 Revision 4.1

December 2006

47 of 48

15 ENHANCED ACTIPHY POWER MANAGEMENT

in addition to the iEEE-specified power-down control bit (Mii Register 0.11), the VSC8221 implements an Enhanced ActiPHY™

power management mode. This mode enables support for power-sensitive applications by utilizing a signal-detect function that

monitors the media interface for the absence of a link to determine when to automatically power-down the PHY. The Station

Manager is in control of this mode. The PHY then ‘wakes up’ at a programmable interval and attempts to ‘wake-up’ the link

partner PHY by sending a fast link pulse (FLP) on the Media interface.

The Enhanced ActiPHY™ power management mode can be set at startup (Refer to Section 18 on page 53 and Section 19 on

page 57 for details) or at any time during normal operation by writing to Mii Register 28.6.

15.1 Operation in Enhanced ActiPHY Mode

There are three PHY operating states when Enhanced ActiPHYTM 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 LP wake up state at a programmable rate (sleep timer) until signal energy

has been detected on the media interface pins. When signal energy is detected, the PHY enters the normal operating state.

When the PHY is in the normal operating state and link is lost, the PHY returns to the low power state after the link status

timeout timer has expired. After reset, the PHY enters the low power state.

When auto-negotiation is enabled in the PHY, the ActiPHYTM state machine will operate as described above. if auto-negotiation

is disabled and the link is forced to 10BT or 100BTX mode while the PHY is in the low power state, the PHY continues to

transition between the low power and LP wakeup 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.

Figure 16. Enhanced ActiPHY State Diagram

Low Power State

LP Wake-up State

Normal Operation

FLP Sent

Sleep timer Expires

Timeout timer expires after

link has been dropped and

auto-negotiation is enabled.

Signal Energy Detect on

Media (CAT5 or Fiber)

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