Datasheet

3.0 Functional Description (Continued)
Subject to change without notice. 22 Rev O www.national.com
DP83815
3.9.3 NRZ to NRZI Encoder
After the transmit data stream has been serialized and
scrambled, the data must be NRZI encoded in order to
comply with the TP-PMD standard for 100BASE-TX
transmission over Category-5 un-shielded twisted pair
cable. There is no ability to bypass this block within the
DP83815.
3.9.4 Binary to MLT-3 Convertor / Common Driver
The Binary to MLT-3 conversion is accomplished by
converting the serial binary data stream output from the
NRZI encoder into two binary data streams with alternately
phased logic one events. These two binary streams are
then fed to the twisted pair output driver which converts the
voltage to current and alternately drives either side of the
transmit transformer primary winding, resulting in a minimal
current (20 mA max) MLT-3 signal. Refer to Figure 3-7
Figure 3-7 Binary to MLT-3 conversion
D
Q
Q
binary_in
binary_plus
binary_minus
binary_in
binary_plus
binary_minus
COMMON
DRIVER
MLT-3
differential MLT-3
Table 3-1 4B5B Code-Group Encoding/Decoding
Name PCS 5B Code-group Description/4B Value
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
J 11000 First Start of Packet - 0101
K 10001 Second Start of Packet - 0101
T 01101 First End of Packet - 0000
R 00111 Second End of Packet - 0000
Obsolete