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LAN8700I

±15kV ESD Protected MII/RMII Fast-Ethernet PHY with HP Auto-MDIX and SMSC flexPWR™ in a Small Footprint

SMSC -> Microchip 

±15kV ESD Protected MII/RMII Fast-Ethernet PHY with HP Auto-MDIX and SMSC flexPWRTM in a Small Footprint

Datasheet

Chapter 4 Architecture Details

4.1

Top Level Functional Architecture

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

„ 100Base-TX transmit and receive

„ 10Base-T transmit and receive

„ MII or RMII interface to the controller

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

„ Management Control to read status registers and write control registers

MAC

TX_CLK

(for M II only)

Ext R ef_C LK (for R M II only)

M II 25 M hz by 4 bits

or

M II

R M II 50M hz by 2 bits

100M

PLL

25MHz

by 4 bits

4 B /5 B

Encoder

25M Hz by S cram bler

5 bits

and PISO

NRZI

C o n ve rte r

NRZI

125 M bps Serial

M LT-3

Converter MLT-3

Tx

D riv e r

MLT-3 M agnetics

M LT -3

RJ45

M LT -3

C A T -5

Figure 4.1 100Base-TX Data Path

4.2

4.2.1

4.2.2

100Base-TX Transmit

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

100M Transmit Data Across the MII/RMII Interface

For MII, the MAC controller drives the transmit data onto the TXD bus and asserts TX_EN to indicate

valid data. The data is latched by the PHY’s MII block on the rising edge of TX_CLK. The data is in

the form of 4-bit wide 25MHz data.

The MAC controller drives the transmit data onto the TXD bus and asserts TX_EN to indicate valid

data. The data is latched by the PHY’s MII block on the rising edge of REF_CLK. The data is in the

form of 2-bit wide 50MHz data.

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.

Revision 1.0 (02-09-07)

18

DATASHEET

SMSC LAN8700/LAN8700I

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