LAN9211 datasheet(68/147 Pages) SMSC

68 / 147 page

High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

4.2.2

Scrambling

Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large

narrow-band peaks. Scrambling the data helps eliminate these peaks and spread the signal power

more uniformly over the entire channel bandwidth. This uniform spectral density is required by FCC

regulations to prevent excessive EMI from being radiated by the physical wiring.

The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data.

4.2.3

NRZI and MLT3 Encoding

The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a

serial 125MHz NRZI data stream. The NRZI is encoded to MLT-3. MLT3 is a tri-level code where a

change in the logic level represents a code bit “1” and the logic output remaining at the same level

represents a code bit “0”.

4.2.4

100M Transmit Driver

The MLT3 data is then passed to the analog transmitter, which launches the differential MLT-3 signal,

on outputs TXP and TXN, to the twisted pair media via a 1:1 ratio isolation transformer. The 10Base-

T and 100Base-TX signals pass through the same transformer so that common “magnetics” can be

used for both. The transmitter drives into the 100

Ω impedance of the CAT-5 cable. Cable termination

and impedance matching require external components.

4.2.5

100M Phase Lock Loop (PLL)

The 100M PLL locks onto reference clock and generates the 125MHz clock used to drive the 125 MHz

logic and the 100Base-Tx Transmitter.

00101

INVALID, RX_ER if during RX_DV

INVALID

01000

INVALID, RX_ER if during RX_DV

INVALID

01100

INVALID, RX_ER if during RX_DV

INVALID

10000

INVALID, RX_ER if during RX_DV

INVALID

Table 4.1 4B/5B Code Table (continued)

CODE

GROUP

SYM

RECEIVER

INTERPRETATION

TRANSMITTER

INTERPRETATION

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