LAN9250 datasheet(223/421 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS00001913A-page 223

LAN9250

12.2.10.1

General Power-Down

This power-down mode is controlled by the Power Down (PHY_PWR_DWN) bit of the PHY Basic Control Register

(PHY_BASIC_CONTROL). In this mode the entire transceiver, except the PHY management control interface, is pow-

ered down. The transceiver will remain in this power-down state as long as the Power Down (PHY_PWR_DWN) bit is

set. When the Power Down (PHY_PWR_DWN) bit is cleared, the transceiver powers up and is automatically reset.

12.2.10.2

Energy Detect Power-Down

This power-down mode is enabled by setting the Energy Detect Power-Down (EDPWRDOWN) bit of the PHY Mode

Control/Status Register (PHY_MODE_CONTROL_STATUS). In this mode, when no energy is present on the line, the

entire transceiver is powered down (except for the PHY management control interface, the SQUELCH circuit and the

ENERGYON logic). The ENERGYON logic is used to detect the presence of valid energy from 100BASE-TX, 10BASE-

T, or Auto-Negotiation signals.

In this mode, when the Energy On (ENERGYON) bit in the PHY Mode Control/Status Register (PHY_MODE_CON-

TROL_STATUS) signal is low, the transceiver is powered down and nothing is transmitted. When energy is received,

via link pulses or packets, the Energy On (ENERGYON) bit goes high, and the transceiver powers up. The transceiver

automatically resets itself into the state prior to power-down, and asserts the INT7 bit of the PHY Interrupt Source Flags

When the Energy Detect Power-Down (EDPWRDOWN) bit of the PHY Mode Control/Status Register (PHY_MODE_-

CONTROL_STATUS) is low, energy detect power-down is disabled.

When in EDPD mode, the device’s NLP characteristics may be modified. The device can be configured to transmit NLPs

in EDPD via the EDPD TX NLP Enable bit of the PHYEDPD NLP / Crossover Time / EEE Configuration Register

(PHY_EDPD_CFG). When enabled, the TX NLP time interval is configurable via the EDPD TX NLP Interval Timer

Select field of the PHYEDPD NLP / Crossover Time / EEE Configuration Register (PHY_EDPD_CFG). When in EDPD

mode, the device can also be configured to wake on the reception of one or two NLPs. Setting the EDPD RX Single

NLP Wake Enable bit of the PHYEDPD NLP / Crossover Time / EEE Configuration Register (PHY_EDPD_CFG) will

enable the device to wake on reception of a single NLP. If the EDPD RX Single NLP Wake Enable bit is cleared, the

maximum interval for detecting reception of two NLPs to wake from EDPD is configurable via the EDPD RX NLP Max

Interval Detect Select field of the PHYEDPD NLP / Crossover Time / EEE Configuration Register (PHY_EDPD_CFG).

The energy detect power down feature is part of the broader power management features of the device and can be used

to trigger the power management event output pin (PME) or general interrupt request pin (IRQ). This is accomplished

by enabling the energy detect power-down feature of the PHY as described above, and setting the energy detect enable

of the Power Management Control Register (PMT_CTRL). Refer to Power Management for additional information.

12.2.11

ENERGY EFFICIENT ETHERNET

The PHY supports IEEE 802.3az Energy Efficient Ethernet (EEE). The EEE functionality is enabled/disabled via the

PHY Energy Efficient Ethernet Enable (PHYEEEEN) bit of the PHYEDPD NLP / Crossover Time / EEE Configuration

configuration strap. In order for EEE to be utilized, the following conditions must be met:

• EEE functionality must be enabled via the PHY Energy Efficient Ethernet Enable (PHYEEEEN) bit of the PHY-

EDPD NLP / Crossover Time / EEE Configuration Register (PHY_EDPD_CFG)

•The 100BASE-TX EEE bit of the MMD PHY EEE Advertisement Register (PHY_EEE_ADV) must be set

• The MAC and link-partner must support and be configured for EEE operation

• The device and link-partner must link in 100BASE-TX full-duplex mode

The value of the PHY Energy Efficient Ethernet Enable (PHYEEEEN) bit affects the default values of the following reg-

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