L80227 LSI, L80227 Datasheet - Page 32

• Manufacturer Part Number: L80227
• Manufacturer: LSI

Specifications of L80227

• Lead Free Status / RoHS Status: Not Compliant

2.3.4.2 Manchester Decoder (10 Mbits/s)
2.3.5 Scrambler
2.3.6 Descrambler
2-14
5B codewords to the 4B nibbles is specified in IEEE 802.3. The 4B5B
decoder takes the 5B codewords from the descrambler, converts them
into 4B nibbles according to
receive Ethernet controller.
The 4B5B decoder also strips off the SSD delimiter (/J/K/ symbols), and
replaces it with two 4B Data 5 nibbles (/5/ symbol). It also strips off the
ESD delimiter (/T/R/ symbols), and replaces it with two 4B Data 0 nibbles
(/I/ symbol), per IEEE 802.3 specifications (see
The 4B5B decoder detects SSD, ESD, and codeword errors in the
incoming data stream as specified in IEEE 802.3. To indicate these
errors, the device asserts the RX_ER output while the errors are being
transmitted across RXD[3:0].
In Manchester coded data, the first half of the data bit contains the
complement of the data, and the second half of the data bit contains the
true data. The Manchester Decoder converts the single data stream from
the TP receiver into non-return to zero (NRZ) data for the controller
interface. To do this, it decodes the data and strips off the SOI pulse.
Because the Clock and Data Recovery block has already separated the
clock and data from the TP receiver, that block inherently performs the
the Manchester decoding.
100BASE-TX transmission requires scrambling to reduce the radiated
emissions on the twisted pair. The scrambler takes the NRZI encoded
data from the 4B5B encoder, scrambles it per the IEEE 802.3
specifications, and sends it to the TP transmitter. A scrambler is not used
for 10 Mbits/s operation.
The descrambler block shown in
100BASE-TX operation. The device descrambler takes the scrambled
NRZI data from the data recovery block, descrambles it according to
IEEE 802.3 specifications, aligns the data on the correct 5B word
boundaries, and sends it to the 4B5B decoder.
Functional Description
Copyright © 2000, 2001, 2002 by LSI Logic Corporation. All rights reserved.
Table
Figure 2.1
2.4, and sends the 4B nibbles to the
is used in
Figure
2.2).