L80227 LSI, L80227 Datasheet - Page 31

• Manufacturer Part Number: L80227
• Manufacturer: LSI

Specifications of L80227

• Lead Free Status / RoHS Status: Not Compliant

2.3.3.1 4B5B Encoder (100 Mbits/s)
2.3.3.2 Manchester Encoder (10 Mbits/s)
2.3.4 Decoder
2.3.4.1 4B5B Decoder (100 Mbits/s)
100BASE-TX operation requires that the data be 4B5B encoded. The
4B5B Encoder block shown in
nibbles into five-bit data words. The mapping of the 4B nibbles to 5B
codewords is specified in IEEE 802.3 and is shown in
The 4B5B encoder takes 4B (four-bit) nibbles from the Transmit MAC
block, converts them into 5B (five-bit) words according to
sends the 5B words to the scrambler. The 4B5B encoder also substitutes
the first eight bits of the preamble with the Start of Stream Delimiter
(SSD) (/J/K/ symbols) and adds an End of Stream Delimiter (ESD) (/T/R/
symbols) to the end of each packet, as defined in IEEE 802.3 and shown
in
(idle period), with a continuous stream of idle symbols, as shown in
Figure
The Manchester Encoder shown in
operation. It combines clock and non-return to zero inverted (NRZI) data
such that 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, as
specified in IEEE 802.3. This process guarantees that a transition always
occurs in the middle of the bit cell. The Manchester encoder on the
device converts the 10 Mbits/s NRZI data from the Ethernet controller
interface into a single data stream for the TP transmitter and adds a start
of idle pulse (SOI) at the end of the packet as specified in IEEE 802.3
and shown in
on actual packet data; during the idle period between packets, no signal
is transmitted except for periodic link pulses.
This section describes the 4B5B decoder, used in 100 Mbits/s operation,
which converts 5B encoded data to 4B nibbles. It also describes the
Manchester Decoder, used in 10BASE-T operation.
Because the TP input data is 4B5B encoded on the transmit side, the
4B5B decoder must decode it on the receive side. The mapping of the
Block Diagram Description
Figure
2.2.
2.2. The 4B5B encoder also fills the period between packets
Figure
Copyright © 2000, 2001, 2002 by LSI Logic Corporation. All rights reserved.
2.2. The Manchester encoding process is only done
Figure 2.1
Figure 2.1
converts the four-bit data
is used for 10 Mbits/s
Table
Table
2.4.
2.4, and
2-13