3.0 Functional Description
(Continued)
20
www.national.com
DP83816
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
DP83816.
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
Summary of Contents for MacPHYTER-II DP83816
Page 106: ...105 www national com DP83816 Notes...