Specifications
DP83848C
,
DP83848I
DP83848VYB, DP83848YB
SNLS266E –MAY 2007–REVISED MARCH 2015
www.ti.com
Table 6-6. 4B5B Code-Group Encoding/Decoding
DATA CODES
0 11110 0000
1 01001 0001
2 10100 0010
3 10101 0011
4 01010 0100
5 01011 0101
6 01110 0110
7 01111 0111
8 10010 1000
9 10011 1001
A 10110 1010
B 10111 1011
C 11010 1100
D 11011 1101
E 11100 1110
F 11101 1111
IDLE AND CONTROL CODES
H 00100 HALT code-group - Error code
I 11111 Inter-Packet IDLE - 0000
(1)
J 11000 First Start of Packet - 0101
(1)
K 10001 Second Start of Packet - 0101
(1)
T 01101 First End of Packet - 0000
(1)
R 00111 Second End of Packet - 0000
(1)
INVALID CODES
V 00000
V 00001
V 00010
V 00011
V 00101
V 00110
V 01000
V 01100
(1) Control code-groups I, J, K, T and R in data fields will be mapped as invalid codes, together with RX_ER asserted.
6.5.1.1.1 Code-group Encoding and Injection
The code-group encoder converts 4-bit (4B) nibble data generated by the MAC into 5-bit (5B) code-groups
for transmission. This conversion is required to allow control data to be combined with packet data code-
groups. Refer to Table 6-6 for 4B to 5B code-group mapping details.
The code-group encoder substitutes the first 8-bits of the 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 packet, upon the
deassertion of Transmit Enable signal from the MAC, the code-group encoder injects the T/R code-group
pair (01101 00111) indicating the end of the frame.
After the T/R code-group pair, the code-group encoder continuously injects IDLEs into the transmit data
stream until the next transmit packet is detected (reassertion of Transmit Enable).
40 Detailed Description Copyright © 2007–2015, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Links: DP83848C DP83848I DP83848VYB DP83848YB