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4.0 Functional Description (Continued)

4.7.9 MLT-3 Converter / DAC / Line Driver

The Binary to MLT-3 conversion is accomplished by con-

verting the serial NRZI data stream output from the NRZI

encoder into two binary data streams with alternately

phased logic one events. These two binary streams are

then passed to a 10/100/1000 DAC and line driver which

converts the pulses to suitable analog line voltages. Refer

to Figure 8.

The 100BASE-TX MLT-3 signal sourced by the MDI+/- line

driver output pins is slew rate controlled. This should be

considered when selecting AC coupling magnetics to

ensure TP-PMD Standard compliant transition times (3 ns

< tr < 5 ns).

The 100BASE-TX transmit TP-PMD function within the

DP83865 outputs only MLT-3 encoded data. Binary data

outputs is not available from the MDI+/- in the 100 Mb/s

mode.

4.7.10 TX_ER

Assertion of the TX_ER input while the TX_EN is also

asserted will cause the DP83865 to substitute HALT code-

groups for the 5B data present at TXD[3:0]. However, the

Start-of-Stream Delimiter (SSD) /J/K/ and End-of-Stream

Delimiter (ESD) /T/R/ will not be substituted with HALT

code-groups. As a result, the assertion of TX_ER while

TX_EN is asserted will result in a frame properly encapsu-

lated with the /J/K/ and /T/R/ delimiters which contains

HALT code-groups in place of the data code-groups.

4.8 10BASE-T and 100BASE-TX Receiver

The 10BASE-T receiver converts Manchester codeing to 4-

bit nibble data to the MII. The 100BASE-TX receiver con-

sists of several sub functional blocks which convert the

scrambled MLT-3 125 Mb/s serial data stream to synchro-

nous 4-bit nibble data that is provided to the MII. The

10/100 Mb/s TP-PMD is integrated with the 1000 Mb/s.

The 10/100 differential input data MDI+/- is routed from

channel B of the isolation magnetics.

See Figure 8 for a block diagram of the 10BASE-T AND

100BASE-TX receive function. It provides an overview of

each functional block within the 10/100 receive section.

The 10BASE-T Receive section consists of the following

functional blocks:

—Receiver

— Clock and Data Recovery

— Manchester Decoder

—Link Detect

The 100BASE-T Receive section consists of the following

functional blocks:

— ADC Block

— Signal Detect

— BLW/EQ/AAC Correction

— Clock Recovery Module

— MLT-3 to NRZ Decoder

— Descrambler

— Serial to Parallel

—5B/4B Decoder

— Code Group Alignment

— Link Integrity Monitor

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