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8 to 10-Bit/10 to 8-Bit Data Conversion With Frame Disparity Generating/ Checking

IP.com Disclosure Number: IPCOM000121483D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 4 page(s) / 97K

Publishing Venue

IBM

Related People

Chao, GT: AUTHOR [+2]

Abstract

10-bit encoded data has been used in the data frames for the optical links. The disparity of this 10-bit data has been defined as follows: Positive Disparity: number of 1s is more than 0s. i.e., 1111001100 Negative Disparity: number of 0s is more than 1s. i.e., 1100001100 Zero Disparity: number of 1s is equal to 0s. i.e., 1100100110

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

8 to 10-Bit/10 to 8-Bit Data Conversion With Frame Disparity Generating/
Checking

      10-bit encoded data has been used in the data frames for
the optical links.  The disparity of this 10-bit data has been
defined as follows:
      Positive Disparity: number of 1s is more than 0s.
                       i.e., 1111001100
      Negative Disparity: number of 0s is more than 1s.
                       i.e., 1100001100
      Zero Disparity: number of 1s is equal to 0s.
                       i.e., 1100100110

      The following conditions are defined as 'Code Violation' in the
10-bit encoded data frames:
      1.   Positive Disparity data is followed by Positive Disparity
data immediately or separated by one or more Zero Disparity data.
      2.   A Negative Disparity data is followed by Negative
Disparity data immediately or separated by one or more Zero Disparity
data.
      3.   No corresponding 8-bit data for this 10-bit data.
(A).  8-Bit to 10-Bit Data Conversion with Frame Disparity Generating

      The following information and the flow chart (Fig. 1) show a
method implemented in the software to convert the outgoing 8-bit data
frame to an encoded 10-bit data frame and also generate the correct
disparity for this frame to avoid the 'Code Violation'.

      Two tables (256 x 16 each) that contain the following data
structure have to be built in either ROM or RAM.  When 8-bit data is
received, it will be used as an offset or an index to access 16-bit
data from either of these tables (dependent upon the previous data's
disparity):
                            POS_DISP_TABLE

      This table contains the 10-bit data that has Positive or Zero
Disparity.
            Bit     15 <--------- 11  10   9 <----------------- 0
                         Don't        DP       Encoded 10-bit
                         care                  data for this
                                         ...