4B5B ENCODING
4B5B ENCODING was purposely invented to
produce at least two transitions per 5 bits of output code regardless of input
data. When it is NRZI-encoded, the transitions give necessary clock transitions for the receiver to
be able to comprehend input data correctly. For example, a run of 4 bits such
as 00002 contains no transitions and that causes clocking problems for the
receiver. 4B5B comes to rescue this problem by assigning the 4-bit block a
5-bit code, in this particular example 111102.
| Data | 4B5B code | |
| (Hex) | (Binary) | |
| 0 | 0 | 11110 |
| 1 | 1 | 1001 |
| 2 | 10 | 10100 |
| 3 | 11 | 10101 |
| 4 | 100 | 1010 |
| 5 | 101 | 1011 |
| 6 | 110 | 1110 |
| 7 | 111 | 1111 |
| 8 | 1000 | 10010 |
| 9 | 1001 | 10011 |
| A | 1010 | 10110 |
| B | 1011 | 10111 |
| C | 1100 | 11010 |
| D | 1101 | 11011 |
| E | 1110 | 11100 |
| F | 1111 | 11101 |
Check out the youtube video for more.
https://youtu.be/97nmHK4DRoA
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