MOTOROLA
Appendix B. 8B/10B Coding Scheme
B-3
Data Tables
5. The positive or negative disparity transmission character (see Figure B-3) is passed
to the transmit driver, available for differentialization (See Section 2.3.1, “Transmit
Driver Operation”).
Figure B-3. Character Transmission
B.1.3 Calculating Running Disparity
Running disparity improves error detection and recovery. The rules for calculating the
running disparity for sub-blocks are as follows (reference Fibre Channel, Gigabit
Communications and I/O for Computer Networks):
•
Running disparity at the end of any sub-block is positive if (1) the encoded
sub-block contains more 1s than 0s, (2) if the 6-bit sub-block is 6’b00 0111, or (3)
if the 4-bit sub-block is 4’b0011.
•
Running disparity at the end of any sub-block is negative if (1) the encoded
sub-block contains more 0 than 1 bits, (2) if the 6-bit sub-block is 6’b11 1000, or (3)
if the 4-bit sub-block is 4’b1100.
•
Otherwise, running disparity at the end of the sub-block is the same as at the
beginning of the sub-block.
B.2 Data Tables
Table B-2 displays the full valid data character 8B/10B codes. The values in the “Data
Value HGFEDCBA” column are the possible bit values of the unencoded transmission
characters. The current RD values are the possible positive and negative running disparity
values.
Direction of Transmission
J
H
G
F
I
E
D
C
B
A
Summary of Contents for MC92603
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