H1102 datasheet(20/54 Pages) MICREL

20 / 54 page

Micrel, Inc.

KSZ8041NL/RNL

September 2010

M9999-090910-1.4

Functional Description

The KSZ8041NL is a single 3.3V supply Fast Ethernet transceiver. It is fully compliant with the IEEE 802.3u Specification.

On the media side, the KSZ8041NL supports 10Base-T and 100Base-TX with HP auto MDI/MDI-X for reliable detection of

and correction for straight-through and crossover cables.

The KSZ8041NL offers a choice of MII or RMII data interface connection with the MAC processor. The MII management

bus option gives the MAC processor complete access to the KSZ8041NL control and status registers. Additionally, an

interrupt pin eliminates the need for the processor to poll for PHY status change.

Physical signal transmission and reception are enhanced through the use of patented analog circuitries that make the

design more efficient and allow for lower power consumption and smaller chip die size.

The KSZ8041RNL is an enhanced RMII version of the KSZ8041NL that does not require a 50MHz system clock. It uses a

25MHz crystal for its input reference clock and outputs a 50MHz RMII reference clock to the MAC.

100Base-TX Transmit

The 100Base-TX transmit function performs parallel-to-serial conversion, 4B/5B coding, scrambling, NRZ-to-NRZI

conversion, and MLT3 encoding and transmission.

The circuitry starts with a parallel-to-serial conversion, which converts the MII data from the MAC into a 125MHz serial bit

stream. The data and control stream is then converted into 4B/5B coding, followed by a scrambler. The serialized data is

further converted from NRZ-to-NRZI format, and then transmitted in MLT3 current output.

The output current is set by an external 6.49k

Ω 1% resistor for the 1:1 transformer ratio. It has typical rise/fall times of 4

ns and complies with the ANSI TP-PMD standard regarding amplitude balance, overshoot and timing jitter. The wave-

shaped 10Base-T output drivers are also incorporated into the 100Base-TX drivers.

100Base-TX Receive

The 100Base-TX receiver function performs adaptive equalization, DC restoration, MLT3-to-NRZI conversion, data and

clock recovery, NRZI-to-NRZ conversion, de-scrambling, 4B/5B decoding, and serial-to-parallel conversion.

The receiving side starts with the equalization filter to compensate for inter-symbol interference (ISI) over the twisted pair

cable. Since the amplitude loss and phase distortion is a function of the cable length, the equalizer must adjust its

characteristics to optimize performance. In this design, the variable equalizer makes an initial estimation based on

comparisons of incoming signal strength against some known cable characteristics, and then tunes itself for optimization.

This is an ongoing process and self-adjusts against environmental changes such as temperature variations.

Next, the equalized signal goes through a DC restoration and data conversion block. The DC restoration circuit is used to

compensate for the effect of baseline wander and to improve the dynamic range. The differential data conversion circuit

converts the MLT3 format back to NRZI. The slicing threshold is also adaptive.

The clock recovery circuit extracts the 125MHz clock from the edges of the NRZI signal. This recovered clock is then used

to convert the NRZI signal into the NRZ format. This signal is sent through the de-scrambler followed by the 4B/5B

decoder. Finally, the NRZ serial data is converted to the MII format and provided as the input data to the MAC.

PLL Clock Synthesizer

The KSZ8041NL/RNL generates 125M

Ηz, 25MΗz and 20MΗz clocks for system timing. Internal clocks are generated

from an external 25MHz crystal or oscillator. For the KSZ8041NL in RMII mode, these internal clocks are generated from

an external 50MHz oscillator or system clock.

Scrambler/De-scrambler (100Base-TX only)

The purpose of the scrambler is to spread the power spectrum of the signal in order to reduce EMI and baseline wander.

10Base-T Transmit

The 10Base-T drivers are incorporated with the 100Base-TX drivers to allow for transmission using the same magnetic.

The drivers also perform internal wave-shaping and pre-emphasize, and output 10Base-T signals with a typical amplitude

of 2.5V peak. The 10Base-T signals have harmonic contents that are at least 27dB below the fundamental frequency

when driven by an all-ones Manchester-encoded signal.

H1102 Datasheet(PDF) 20 Page - Micrel Semiconductor

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