MC9S12NE64_06 Datasheet, PDF (376/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 12 Ethernet Physical Transceiver (EPHYV2)
restoration to restore the lost DC component of the recovered digital data to correct the baseline wander
problem.
Timing Recovery: The timing recovery block locks onto the incoming data stream, extracts the embedded
clock, and presents the data synchronized to the recovered clock.
In the event that the receive path is unable to converge to the receive signal, it resets the MSE-good (bit
25.15) signal. The clock synthesizer provides a center frequency reference for operation of the clock
recovery circuit in the absence of data.
Adaptive Equalizer: At a data rate of 125 Mbps, the cable introduces significant distortion due to high
frequency roll off and phase shift. The high frequency loss is mainly due to skin effect, which causes the
conductor resistance to rise as the square of the frequency.
The adaptive equalizer will compensate for signal amplitude and phase distortion incurred from
transmitting with different cable lengths.
Loopback: If asserted by bit 0.14, data encoded by the MLT3 encoder block is looped back to the MLT3
decoder block while the transmit and receive paths are disconnected from the media.
A second loopback mode for 100BASE-TX is available by setting bit 18.13 (MII loopback) to a logical 1.
This loopback mode takes the MII transmit data and loops it directly back to the MII receive pins. Again,
the transmit and receive paths are disconnected from the media.
MII loopback has precedence over the digital loopback if both are enabled at the same time.
A third loopback mode is available by setting bit 18.4 high. This analog loopback mode takes the MLT3
encoded data and loops it back through the base line wander and analog receive circuits.
Line Transmitter and Line Receiver: These analog blocks allow EPHY to drive and receive data to/from
the 100BASE-TX media. The transmitter is designed to drive a 100-Ω UTP cable.
Link Monitor: The link monitor process is responsible for determining whether the underlying receive
channel is providing reliable data. If a failure is found, normal operation will be disabled. As specified in
the IEEE 802.3 standard, the link is operating reliably if a signal is detected for a period of 330 µs.
Far End Fault: While the auto-negotiation function is disabled, this function is used to exchange fault
information between the PHY and the link partner.
12.4.5 Low Power Modes
There are several reduced power configurations available for the EPHY.
12.4.5.1 Stop Mode
If the MCU executes a STOP instruction, the EPHY will be powered down and all internal MII registers
reset to their default state. Upon exiting stop mode, the EPHY will exit the power-down state and latch the
values previously written to the EPHYCTL0 and EPHYCTL1 registers. The MII registers will have to be
re-initialized after the start-up delay (t_Start-up) has expired.
MC9S12NE64 Data Sheet, Rev. 1.1
376
Freescale Semiconductor