N in, Figure a–2 – Altera Stratix GX Transceiver User Manual
Page 286
A–2
Altera Corporation
Stratix GX Transceiver User Guide
January 2005
8B/10B Code
Figure A–2. 10-Bit Grouping of 6-Bit & 4-Bit Sub-Blocks
The running disparity at the beginning of the 6-bit sub-block is the
running disparity at the end of the previous 10-bit code. The running
disparity of the 4-bit sub-block is the running disparity of the end of the
6-bit sub-block. The running disparity of the end of the 4-bit sub-block is
the running disparity of the 10-bit code, as shown in
Figure A–3. Running Disparity Between Sub-Blocks
The running disparity calculation rules are as follows (if the conditions
are not met, then the running disparity at the end of the sub-blocks are the
same as the beginning of the sub-block):
■
The current running disparity at the end of a sub-block is positive if
any of the following are true:
●
The sub-block contains more ones than zeros.
●
The 6-bit sub-block is 6'b000111.
●
The 4-bit sub-block is 4'b0011.
■
The current running disparity at the end of a sub-block is negative if
any of the following are true:
●
The sub-block contains more zeros than ones.
●
The 6-bit sub-block is 6'b111000.
●
The 4-bit sub-block is 4'b1100.
7
6
5
4
3
2
1
0
9
8
g
f
i
e
d
c
b
a
j
h
6-Bit Block
4-Bit Block
10-Bit Code
0
0
0
1
1
1
0
0
0
1
6-Bit Block
4-Bit Block
10-Bit Code
0
0
1
1
0
1
0
1
1
1
6-Bit Block
4-Bit Block
10-Bit Code
RD+
RD+
RD+
RD-
1st Bit
Received
Last Bit
Received