KSZ8563R datasheet(19/221 Pages) MICROCHIP

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DS00002418D-page 19

KSZ8563R

4.1.1.3

Scrambler/De-Scrambler

The purpose of the scrambler is to spread the power spectrum of the signal to reduce electromagnetic interference (EMI)

and baseline wander. The scrambler is used only for 100BASE-TX.

Transmitted data is scrambled through the use of an 11-bit wide linear feedback shift register (LFSR). The scrambler

generates a 2047-bit non-repetitive sequence. Then the receiver de-scrambles the incoming data stream using the

same sequence as at the transmitter.

4.1.2

10BASE-T/Te TRANSCEIVER

When the AVDDH supply is 3.3V, the 10Mbps interface is 10BASE-T. When AVDDH is 2.5V, the 10BASE-T signal has

a reduced amplitude and is known as 10BASE-Te. 10BASE-Te is interoperable with 10BASE-T when Cat5 cable is

used.

4.1.2.1

10BASE-T/Te Transmit

The 10BASE-T/Te driver is incorporated with the 100BASE-TX driver to allow for transmission using the same magnet-

ics. They are internally wave-shaped and pre-emphasized into outputs with typical 2.5V amplitude for 10BASE-T, or

1.75V amplitude for 10BASE-Te. The harmonic contents are at least 27dB below the fundamental frequency when

driven by an all-ones Manchester-encoded signal.

4.1.2.2

10BASE-T/Te Receive

On the receive side, input buffers and level detecting squelch circuits are employed. A differential input receiver circuit

and a phase-locked loop (PLL) perform the decoding function.

The Manchester-encoded data stream is separated into clock signal and NRZ data. A squelch circuit rejects signals with

levels less than 400mV or with short pulse widths to prevent noise at the RXP1 or RXM1 input from falsely triggering

the decoder. When the input exceeds the squelch limit, the PLL locks onto the incoming signal and the device decodes

a data frame. The receiver clock is maintained active during idle periods in between data reception.

4.1.3

AUTO MDI/MDI-X

The automatic MDI/MDI-X feature, also known as auto crossover, eliminates the need to determine whether to use a

straight cable or a crossover cable between the device and its link partner. The auto-sense function detects the MDI/

MDI-X pair mapping from the link partner, and assigns the MDI/MDI-X pair mapping of the device accordingly. Table 4-

1 shows the device’s 10/100 Mbps pin configuration assignments for MDI and MDI-X pin mapping.

Auto MDI/MDI-X is enabled by default. It can be disabled through the port control registers. If Auto MDI/MDI-X is dis-

abled, the port control register can also be used to select between MDI and MDI-X settings.

An isolation transformer with symmetrical transmit and receive data paths is recommended to support Auto MDI/MDI-X.

4.1.4

WAVE SHAPING, SLEW-RATE CONTROL, AND PARTIAL RESPONSE

In communication systems, signal transmission encoding methods are used to provide the noise-shaping feature and

to minimize distortion and error in the transmission channel.

• For 100BASE-TX, a simple slew-rate control method is used to minimize EMI.

• For 10BASE-T/Te, pre-emphasis is used to extend the signal quality through the cable.

4.1.5

AUTO-NEGOTIATION

The device conforms to the auto-negotiation protocol as described by IEEE 802.3. Auto-negotiation allows each port to

operate at either 10BASE-T/Te or 100BASE-TX by allowing link partners to select the best common mode of operation.

During auto-negotiation, the link partners advertise capabilities across the link to each other and then compare their own

TABLE 4-1:

MDI/MDI-X PIN DEFINITIONS

Pin (RJ45 pair)

MDI

MDI-X

100BASE-TX

10BASE-T/Te

100BASE-TX

10BASE-T/Te

TXxP/M (1,2)

TX+/-

RX+/-

RXxP/M (3,6)

RX+/-

TX+/-

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