The block diagram in Figure 6. provides an overview of
each functional block within the 100BASE-TX transmit sec-
tion.
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:
The Transmitter section consists of the following functional
blocks:
— Code-group Encoder and Injection block
— Scrambler block (bypass option)
— 100BASE-TX Transmitter
— 100BASE-TX Receiver
— NRZ to NRZI encoder block
— 10BASE-T Transceiver Module
— 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
DP83848I implements the 100BASE-TX transmit state
machine diagram as specified in the IEEE 802.3u Stan-
dard, Clause 24.
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.
TX_CLK
TXD[3:0] /
TX_EN
DIVIDE
BY 5
4B5B CODE-
GROUP
ENCODER &
5B PARALLEL
TO SERIAL
125MHZ CLOCK
SCRAMBLER
MUX
BP_SCR
MLT[1:0]
100BASE-TX
LOOPBACK
NRZ TO NRZI
ENCODER
BINARY
TO MLT-3 /
COMMON
DRIVER
PMD OUTPUT PAIR
Figure 6. 100BASE-TX Transmit Block Diagram
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24
TI [ TEXAS INSTRUMENTS ]
