LAN9250 datasheet(175/421 Pages) MICROCHIP

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DS00001913A-page 175

LAN9250

The Host MAC maintains a counter, EEE TX LPI Time, that counts (in us) the amount of time that TX LPI request to the

PHY is asserted. Note that this counter does not include the time specified in the Host MAC EEE Time Wait TX System

the Host MAC Energy Efficient Ethernet (HMAC_EEE_ENABLE) bit in the Host MAC Control Register (HMAC_CR) is

low.

11.13.2

RX LPI DETECTION

Receive Lower Power Idle (LPI) is indicated by the PHY to the MAC using the MII value of RXDV=0, RXER=1,

TXD[3:0]=4’b0001.

11.13.2.1

Decoding LPI

The MAC will decode the LPI indication only when Host MAC Energy Efficient Ethernet (HMAC_EEE_ENABLE) is set

in the Host MAC Control Register (HMAC_CR), and if the current speed is 100Mbs, the current duplex is full (as indi-

cated by the Full Duplex Mode (FDPX) bit of the Host MAC Control Register (HMAC_CR)) and the auto-negotiation

result indicates that both the local and partner device supports EEE at 100Mbs. In order to prevent an unstable link con-

dition, the PHY link status also must indicate “up” for one second is set.) before LPI is decoded.

11.13.2.2

RX LPI Counters

The Host MAC maintains a counter, EEE RX LPI Transitions, that counts the number of times that the LPI indication

from the PHY changes from de-asserted to asserted. The counter is not writable and does not clear on read. The counter

is reset if the Host MAC Energy Efficient Ethernet (HMAC_EEE_ENABLE) bit in the Host MAC Control Register

(HMAC_CR) is low.

The Host MAC maintains a counter, EEE RX LPI Time, that counts (in us) the amount of time that the PHY indicates

LPI. The counter is not writable and does not clear on read. The counter is reset if the Host MAC Energy Efficient Ether-

net (HMAC_EEE_ENABLE) bit in the Host MAC Control Register (HMAC_CR) is low.

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