LAN9211 datasheet(66/147 Pages) SMSC

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

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

Chapter 4 Internal Ethernet PHY

4.1

Top Level Functional Description

Functionally, the internal PHY can be divided into the following sections:

100Base-TX transmit and receive

10Base-T transmit and receive

Internal MII interface to the Ethernet Media Access Controller

Auto-negotiation to automatically determine the best speed and duplex possible

Management Control to read status registers and write control registers

Figure 4.1 100Base-TX Data Path

4.2

100Base-TX Transmit

The data path of the 100Base-TX is shown in Figure 4.1. Each major block is explained below.

4.2.1

4B/5B Encoding

The transmit data passes from the MII block to the 4B/5B encoder. This block encodes the data from

4-bit nibbles to 5-bit symbols (known as “code-groups”) according to Table 4.1. Each 4-bit data-nibble

is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used for

control information or are not valid.

The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles,

0 through F. The remaining code-groups are given letter designations with slashes on either side. For

example, an IDLE code-group is /I/, a transmit error code-group is /H/, etc.

The encoding process may be bypassed by clearing bit 6 of register 31. When the encoding is

bypassed the 5th transmit data bit is equivalent to TX_ER.

MAC

Driver

MLT-3

Converter

NRZI

Converter

4B/5B

Encoder

Magnetics

CAT-5

RJ45

100M

PLL

Internal

MII 25 MHz by 4 bits

TX_CLK

25MHz by

5 bits

NRZI

MLT-3

Scrambler

and PISO

125 Mbps Serial

MII

25MHz

by 4 bits

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