VSC7440 datasheet(49/444 Pages) MICROSEMI

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Functional Descriptions

VMDS-10492 VSC7440 Datasheet Revision 4.2

3.8.2.7

Energy Efficient Ethernet

The integrated transceivers support IEEE 802.3az Energy Efficient Ethernet (EEE). This standard

provides a method for reducing power consumption on an Ethernet link during times of low use.

Figure 11 •

Low Power Idle Operation

Using LPI, the usage model for the link is to transmit data as fast as possible and then return to a low

power idle state. Energy is saved on the link by cycling between active and low power idle states. Power

is reduced during LPI by turning off unused circuits and, using this method, energy use scales with

bandwidth utilization.

The transceivers use LPI to optimize power dissipation in 100BASE-TX and 1000BASE-T operation. In

addition, IEEE 802.3az defines a 10BASE-Te mode that reduces transmit signal amplitude from 5 V to

approximately 3.3 V, peak-to-peak. This mode reduces power consumption in 10 Mbps link speed and

can fully interoperate with legacy 10BASE-T compliant PHYs over 100 m Cat5 cable or better.

To configure the transceivers in 10BASE-Te mode, set PHY_EEE_CTRL.EEE_LPI_RX_100BTX_DIS to

1 for each port. Additional Energy Efficient Ethernet features are controlled through Clause 45 registers

as defined in Clause 45 registers to Support Energy Efficient Ethernet

3.8.3

Wake-On-LAN and SecureOn

The device supports Wake-on-LAN, an Ethernet networking standard to awaken hosts by using a “magic

packet” that is decoded to ascertain the source, and then assert an interrupt pin or an LED. The device

also supports SecureOn to secure Wake-on-LAN against unauthorized access. The following illustration

shows an overview of the Wake-on-LAN functionality.

Figure 12 •

Wake-On-LAN Functionality

Wake-on-LAN detection is available in 10BASE-T, 100BASE-TX, and 1000BASE-T modes., It is enabled

by setting the interrupt mask register PHY_INT_MASK. WOL_INT_ENA and its status is read in the

interrupt status register PHY_INT_STAT. WOL_INT_PEND. Wake-on-LAN and SecureOn are configured

for each port using the PHY_WOL_MDINT_CTRL register. The MAC address for each port is saved in its

local register space (PHY_WOL_MAC_ADDRx).

Active

Low-Power Idle

Active

Quiet

Tx Path

Rx Path

Wake-on-LAN

Detect

WOL_MAC_ADDR

ADDR_REPEAT_CNT

Secure-On enable

Secure-On

password length

Secure-On password

WoL Detected

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