Talk:4B5B

Category

This article should be listed in http://en.wikipedia.org/wiki/Category:Line_codes.

Done. --68.0.120.35 19:08, 7 December 2006 (UTC)

---

5b6b code

There's also a 5b6b code, used by some IEEE 802 class standard. A 5-bit input block makes a 6-bit , DC-balanced output block.

Output blocks are either DC-balanced (overall disparity 0), or are assigned in pairs, (overall disparity ±2). The latter codes are assigned in pairs, and the member of the pair chosen that will drive the running disparity toward 0.

Because input blocks have an odd number of bits, they always have an odd disparity. Blocks with a disparity of ±1 are output by appending one more bit, chosen to make the overall disparity 0.

Blocks with disparities ±3 and ±5 are assigned pairs of codes, as follows. Note that the pairs are bitwise complements, so the encoder only needs to store one value, and optionally invert it.

Input	Output
00000	010111	101000
00001	100111	011000
00010	011011	100100
00100	101011	010100
01000	110011	001100
10000	011101	100010
11110	110110	001001
11101	101110	010001
11011	111001	000110
10111	110101	001010
01111	101101	010010
11111	111010	000101

Why (0,3) RLL, when GCR gives (0,2) RLL?

One thing that's puzzled me is why FDDI chose a code with up to three zeros between ones (sync edges), when codes were already known (GCR) that limited. Does it have something to do with DC bias? But the code isn't DC-balanced... 71.41.210.146 (talk) 14:01, 13 March 2009 (UTC)

FDDI control codes

FDDI uses TT as Ending Delimiter for Tokens

FDDI uses TRRR as minimum End of Frame Sequence for Data Frames

Repeaters may change an R to an S

A received Data Frame is invalid if the first two symbols of the End of Frame Sequence are not TR

FDDI-II defines other control code sequences for Cycle Control and for Tokens and Data within the Packet Channel

71.117.221.89 (talk) 20:16, 11 June 2010 (UTC)

Question re the command codes

Looking at the QQ code -- all zeroes -- therefore no transistions similarly QH and HQ -- only one transtion ?don't these "break" the idea of having two transistions Feldercarb (talk) 15:05, 11 September 2016 (UTC)

Line code or block code

I have edited to avoid calling 4b5b a block code because Block code is something with error correction. Line code doesn't quite hit me right either because MLT-3 encoding is definitely a line code and 4b5b is use in conjunction with MLT-3 in Fast Ethernet. Well, at least now we're giving both 4b5b and 8b10b the same description. Any further improvements or discussion are welcomed. ~Kvng (talk) 21:39, 11 September 2017 (UTC)