Altera Stratix GX Transceiver - Manual (Page 285)

Altera Corporation A–1
January 2005
Appendix A. Data & Control
Codes
8B/10B Code This appendix provides information about the data and control codes for
the Stratix
® GX device.
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 2 groups, x and y, where x is the 5 lower bits
(E D C B A) and y is the upper 3 bits (H G F).
Figure A–1 shows the
notation for 3C hexadecimal.
Figure A–1. Sample Notation for 3C Hexadecimal
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
can have either a neutral disparity or a non-neutral disparity. In the case
of a neutral disparity, 2 neutral disparity 10-bit codes are associated with
an 8-bit code. In the case of a 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 with the RD- column, and
the negative disparity 10-bit code is associated with 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 2 sub blocks, a 6-bit sub-block
(abcdei) and a 4-bit sub-block (fghj), as shown in
Figure A–2 .
0 0 1 1 1 1 0 0
H G F E D C B A
D28.1
(3C hex)
x=28 y = 1
=