LAN9420I-NU Standard Microsystems (SMSC), LAN9420I-NU Datasheet - Page 65

• Manufacturer Part Number: LAN9420I-NU
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LAN9420I-NU

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (max): 3.6V
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 128
• Lead Free Status / RoHS Status: Compliant

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
SMSC LAN9420/LAN9420i
3.6.1
3.6.1.1
GROUP
CODE
01001
10100
10101
01010
01011
01110
11110
01111
MAC
Converter
100BASE-TX Transmit
The data path of the 100BASE-TX is shown in
4B/5B Encoding
The transmit data passes from the MII block to the 4B/5B encoder. This block encodes the data from
4-bit nibbles to 5-bit symbols (known as “code-groups”) according to
is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used for
control information or are not valid.
The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles,
0 through F. The remaining code-groups are given letter designations with slashes on either side. For
example, an IDLE code-group is /I/, a transmit error code-group is /H/, etc.
The encoding process may be bypassed by clearing bit 6 of register 31. When the encoding is
bypassed, the 5
NRZI
RJ45
SYM
0
1
2
3
4
5
6
7
MII 25 MHz by 4 bits
TX_CLK
NRZI
Internal
th
MLT-3
transmit data bit is equivalent to TX_ER.
0
1
2
3
4
5
6
7
Converter
MLT-3
Figure 3.25 100BASE-TX Data Path
INTERPRETATION
100M
Table 3.21 4B/5B Code Table
PLL
CAT-5
RECEIVER
0000
0001
0010
0011
0100
0101
0110
0111
DATASHEET
125 Mbps Serial
MII
MLT-3
MLT-3
65
by 4 bits
Driver
25MHz
Figure
Tx
DATA
3.25. Each major block is explained below.
Encoder
4B/5B
MLT-3
0
1
2
3
4
5
6
7
Magnetics
Table
25MHz by
INTERPRETATION
5 bits
TRANSMITTER
3.21. Each 4-bit data-nibble
0000
0001
0010
0100
0101
0011
0110
0111
Scrambler
and PISO
Revision 1.4 (12-17-08)
DATA