Table 5. 4B5B CCode-group Encoding and Injection
6.
DATA CODES
0
11110
01001
10100
10101
01010
01011
01110
01111
10010
10011
10110
10111
11010
11011
11100
11101
0000
1
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
2
3
4
5
6
7
8
9
A
B
C
D
E
F
IDLE AND CONTROL CODES
H
00100
11111
11000
10001
01101
00111
HALT code-group - Error code
I
Inter-Packet IDLE - 0000 (Note 1)
First Start of Packet - 0101 (Note 1)
Second Start of Packet - 0101 (Note 1)
First End of Packet - 0000 (Note 1)
Second End of Packet - 0000 (Note 1)
J
K
T
R
INVALID CODES
V
V
V
V
V
V
V
V
00000
00001
00010
00011
00101
00110
01000
01100
Note: Control code-groups I, J, K, T and R in data fields will be mapped as invalid codes, together with RX_ER as-
serted.
The code-group encoder converts 4-bit (4B) nibble data code-group pair (01101 00111) indicating the end of the
generated by the MAC into 5-bit (5B) code-groups for frame.
transmission. This conversion is required to allow control
After the T/R code-group pair, the code-group encoder
data to be combined with packet data code-groups. Refer
continuously injects IDLEs into the transmit data stream
to Table 5 for 4B to 5B code-group mapping details.
until the next transmit packet is detected (reassertion of
The code-group encoder substitutes the first 8-bits of the Transmit Enable).
MAC preamble with a J/K code-group pair (11000 10001)
upon transmission. The code-group encoder continues to
replace subsequent 4B preamble and data nibbles with
corresponding 5B code-groups. At the end of the transmit
4.1.1 Scrambler
The scrambler is required to control the radiated emissions
at the media connector and on the twisted pair cable (for
packet, upon the deassertion of Transmit Enable signal
from the MAC, the code-group encoder injects the T/R
25
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