Altera Corporation
6–3
October 2007
Stratix II GX Device Handbook, Volume 2
Specifications & Additional Information
8B/10B Code
This section provides information about the data and control codes for
Stratix II GX devices.
Code Notation
The 8B/10B data and control codes are referred to as Dx.y and Kx.y,
respectively. The 8-bit byte (H G F E D C B A, where H is the MSB and A
is the LSB) is broken up into two groups, x and y, where x is the five lower
bits (E D C B A) and y is the upper three bits (H G F).
Figure 6–1
shows
the designation for 3C hex.
Figure 6–1. Sample Notation for 3C hex
There are 256 Dx.y and 12 Kx.y valid 8-bit codes. These codes have two
10-bit equivalent codes associated with each 8-bit code. The 10-bit codes
have either a neutral disparity or a non-neutral disparity. With neutral
disparity, two neutral disparity 10-bit codes are associated with an 8-bit
code. With non-neutral disparity 10-bit code, a positive and a negative
disparity code are associated with the 8-bit code.
The positive disparity 10-bit code is associated in the RD- column. The
negative disparity 10-bit code is associated in the RD+ column.
Disparity Calculation
The running disparity is calculated based on the sub-blocks of the 10-bit
code. The 10-bit code is divided into two sub blocks, a 6-bit sub-block
(abcdei) and a 4-bit sub-block (fghj), as shown in
Figure 6–2
.
Figure 6–2. 10-Bit Grouping of 6-bit and 4-Bit Sub-Blocks
0
0
1
1
1
1
y = 1
x = 28
0
0
H
G
F
E
D
C
B
A
D28.1
(3C hex)
=
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