KSZ9563R datasheet(50/226 Pages) MICROCHIP

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KSZ9563R

DS00002419D-page 50

 2017-2018 Microchip Technology Inc.

4.8.1

NORMAL OPERATION MODE

At power-up, the device enters into Normal operation mode. It is also selected via bits [4:3] = 00 in the Power Down

Control 0 Register. When the device is in normal operation mode, all PLL clocks are running, PHYs and MACs are on,

and the CPU is ready to read or write the device registers through the serial interface (SPI, I2C or MIIM).

During normal operation mode, the host processor can change the power management mode bits in the Power Down

Control 0 Register to transition to any of the other power management modes.

4.8.2

ENERGY-DETECT MODE

Energy-detect mode, also known as energy-detect power down (EDPD) mode, is enabled by setting bits [4:3] to 01 in

the Power Down Control 0 Register. Energy-detect mode provides a mechanism to save power when the device is not

connected to an active link partner. Auto-negotiation must be enabled when in energy-detect mode.

Energy-detect mode consists of two states, normal-power state and low-power state. When the device is in this mode,

it will monitor the cable energy. If there is no energy on the cable for a time longer than a pre-configured value, the device

will go into the low-power state. While in low-power state, the device reduces power consumption by disabling all cir-

cuitry except the energy-detect circuitry of the receiver, which consumes minimal power. When the device is in the low-

power state, it will transmit link pulses at long intervals, with a very low duty cycle. At the same time, it continuously

monitors for energy on the cable. Once energy is detected from the cable and is present for a time longer than 100ns,

the device will enter the normal-power state.

4.8.3

GLOBAL SOFT POWER-DOWN MODE

Soft power-down mode is used to power down the device when it is not in use after power-up. This mode disables all

internal functions except for the serial (SPI or I2C) management interface.

When soft power-down mode is exited, all registers are reset to their default values, and all strap-in pins are sampled

to set the device settings.

4.8.4

PORT-BASED POWER DOWN

Unused ports may be powered down individually to save power.

4.8.5

ENERGY EFFICIENT ETHERNET (EEE)

Energy-efficient Ethernet (EEE) is implemented in the device as described in the IEEE 802.3AZ specification for PHY

ports 1 and 2 only. EEE is not available on port 3. EEE saves power by keeping the voltage on the Ethernet cable at

approximately 0V for as often as possible during periods of no traffic activity. This is called the low-power idle (LPI) state.

However, the link will respond automatically when traffic resumes and do so in such a way as to not cause blocking or

dropping of any packets (the wake-up time for 100BASE-TX is specified to be less than 30µs). The transmit and receive

directions are independently controlled.

The EEE feature is disabled by default. EEE must be auto-negotiated, and is enabled only if both nodes on a link support

it.

The time during which LPI mode is active is called quiet time. This is shown in Figure 4-10.

FIGURE 4-10:

TRAFFIC ACTIVITY AND EEE

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