6–4
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
8B/10B Code
The running disparity at the beginning of the 6-bit sub-block is 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 (refer to
Figure 6–3
).
Figure 6–3. Running Disparity Between Sub-Blocks
The running disparity calculation rules are as follows:
■
The current running disparity at the end of a sub-block is positive if
any of the following is 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 is 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
If those conditions are not met, the running disparity at the end of the
sub-block is the same as at the beginning of the sub-block.
Supported Codes
The 8B/10B scheme defines the 12 control codes listed in
Table 6–2
for
synchronization, alignment, and general application purposes.
0
0
1
1
1
1
1
0
0
j
h
g
f
i
e
d
c
b
0
a
D28.1
(3C hex)
=
10-Bit Code
10-Bit Code
4-Bit Block
4-Bit Block
6-Bit Block
6-Bit Block
Table 6–2. Supported K Codes (Part 1 of 2)
K Code
Octal Value
8-Bit Code
HGF_EDCBA
10-Bit Code RD-
abcdei_fghj
10-Bit Code RD+
abcdei_fghj
K28.0
1C
8’b000_11100
10’b001111_0100
10’b110000_1011
K28.1
3C
8’b001_11100
10’b001111_1001
10’b110000_0110
K28.2
5C
8’b010_11100
10’b001111_0101
10’b110000_1010