LAN9116 Datasheet, PDF (47/109 Pages) SMSC Corporation – Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller

LAN9116
TABLE 4-1: 4B/5B CODE TABLE
Code Group
SYM
Receiver Interpretation
Transmitter Interpretation
11110
01001
10100
10101
01010
01011
01110
01111
10010
10011
10110
10111
11010
11011
11100
11101
11111
11000
10001
01101
00111
00100
00110
11001
00000
00001
00010
00011
00101
01000
01100
10000
0
0
0000
DATA
0
0000
DATA
1
1
0001
1
0001
2
2
0010
2
0010
3
3
0011
3
0011
4
4
0100
4
0100
5
5
0101
5
0101
6
6
0110
6
0110
7
7
0111
7
0111
8
8
1000
8
1000
9
9
1001
9
1001
A
A
1010
A
1010
B
B
1011
B
1011
C
C
1100
C
1100
D
D
1101
D
1101
E
E
1110
E
1110
F
F
1111
F
1111
I
IDLE
Sent after /T/R until TX_EN
J
First nibble of SSD, translated to “0101” Sent for rising TX_EN
following IDLE, else RX_ER
K
Second nibble of SSD, translated to
“0101” following J, else RX_ER
Sent for rising TX_EN
T
First nibble of ESD, causes de-assertion Sent for falling TX_EN
of CRS if followed by /R/, else assertion of
RX_ER
R Second nibble of ESD, causes
Sent for falling TX_EN
deassertion of CRS if following /T/, else
assertion of RX_ER
H Transmit Error Symbol
Sent for rising TX_ER
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
V
INVALID, RX_ER if during RX_DV
INVALID
4.2.2 SCRAMBLING
Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large narrow-band
peaks. Scrambling the data helps eliminate these peaks and spread the signal power more uniformly over the entire
channel bandwidth. This uniform spectral density is required by FCC regulations to prevent excessive EMI from being
radiated by the physical wiring.
The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data.
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DS00002268A-page 47