DP83848J datasheet(21/72 Pages) NSC

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4.0 Architecture

This section describes the operations within each trans-

ceiver module, 100BASE-TX and 10BASE-T. Each opera-

tion consists of several functional blocks and described in

the following:

— 100BASE-TX Transmitter

— 100BASE-TX Receiver

— 10BASE-T Transceiver Module

4.1 100BASE-TX TRANSMITTER

The 100BASE-TX transmitter consists of several functional

blocks which convert synchronous 4-bit nibble data, as pro-

vided by the MII, to a scrambled MLT-3 125 Mb/s serial

data stream. Because the 100BASE-TX TP-PMD is inte-

grated, the differential output pins, PMD Output Pair, can

be directly routed to the magnetics.

The block diagram in Figure 6. provides an overview of

each functional block within the 100BASE-TX transmit sec-

tion.

The Transmitter section consists of the following functional

blocks:

— Code-group Encoder and Injection block

— Scrambler block (bypass option)

— NRZ to NRZI encoder block

— Binary to MLT-3 converter / Common Driver

The bypass option for the functional blocks within the

100BASE-TX transmitter provides flexibility for applications

where data conversion is not always required. The

DP83848J implements the 100BASE-TX transmit state

machine diagram as specified in the IEEE 802.3u Stan-

dard, Clause 24.

Figure 6. 100BASE-TX Transmit Block Diagram

4B5B CODE-

GROUP

ENCODER &

SCRAMBLER

NRZ TO NRZI

ENCODER

5B PARALLEL

TO SERIAL

PMD OUTPUT PAIR

TX_CLK

TXD[3:0] /

TX_EN

BINARY

TO MLT-3 /

COMMON

DRIVER

125MHZ CLOCK

BP_SCR

MUX

100BASE-TX

LOOPBACK

MLT[1:0]

DIVIDE

BY 5

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