Talk:Differential Manchester encoding

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It has been suggested that Differential Manchester encoding be merged with Biphase Mark Code.


I have come directly to the Differential Manchester encoding section, and I have no knowledge of Biphase Mark Code, nor do I have any desire to read about it. Therefore, it is my opinion that the two pages should be left separate.

Aside, the 'Line coding' section should have links to both Differential Manchester encoding and Biphase Mark Code.

- Wickedpygmy

I agree with 'Wickedpygmy'. I only wanted to know the differece between Differential Manchester encoding and Manchester encoding. Keep it serperated ;)

- Kanarie

Fair enough. I do agree with you, however the codes are nearly identical. Basically the clock transition is swapped with the data-carrying transition. In BMC, the presence of a transition mid-bit indicates one state, and the omission indicates the other, whereas there is always a transition at the start of the bit. In BMC the data is carried on the period *after* its corresponding clock transition, in DM it's carried on the period *before* its corresponding clock. It becomes clear why a merge (might) be beneficial; the encodings are almost exactly the same.

Re: categorization, I agree and I'll fix this now if I can find it


The codes are different. It must be kept separate. Things can not be "exactly the same" and ""almost" it at same time. We are talking about exact science. The codes are different.

6 and half a dozen are exactly the same. 6 and 5.9999 are NOT the same.

AES and CDs do not care about Diferential Manchester, and DO USE Biphase Mark encoding.

My two drops. Hisatugo.


As far as I can tell "differential Manchester" and "biphase mark code" are synonyms for exactly the same thing. So I strongly feel their articles should be merged.
If you feel that there is some difference between them, please give an example signal where a biphase mark code receiver would decode a different bit sequence than a differential Manchester receiver. --76.209.28.72 19:20, 5 June 2007 (UTC)

I also think, that they are exactly the same. If you look at the two pictures [1] and [2] you will notice that they are equal, except for their sign and a negative delay of half a clock cycle (which doesn't make any protocol difference). In the differential manchester encoding seen on the image, a 0 causes a rising or falling edge half of a clock cycle before, while a 1 suppresses an edge at that position. In the BMC encoding seen on the other image, a 1 causes a rising or falling edge, while a 0 suppresses an edge. In both codes there are mandatory edges every full clock cycle, while the presence of an edge between those mandatory edges is directly encoding the data. Given the fact that an inverse encoding can be done in both differential manchester and BMC encoding, the two encodings are two different definitions of the same thing.

Btw. 5.9999999... with an infinite amount of nines following IS in fact 6. As the infinite Sum of 9/10 + 9/100 + 9/1000 + ... equals 1.

85.179.40.181 13:38, 4 December 2007 (UTC)

[edit] Where to start?

As the shape of a bit depends on its preceding bit, I guess there is a need for a definition of how the first bit has to look like. --Abdull 18:51, 9 July 2007 (UTC)

This is usually implementation dependent. It is the presence or absence of a transition that encodes data, which only implicitly relies on the previous state of the line. In a real system, there will be a natural 'idle' state of the line when the system is started up, and the first transition will deviate from this state. There may be other implementation and physical layer dependencies that crop up in certain cases as well, but in general there is an obvious and/or specified state that the line will be in at startup and when no data is present. Does that answer your question?
I suppose it may be worthy of mention in the article, but I'm really on the fence. The actual conditions depend heavily on the physical medium in use, and vary from case to case.
--Ktims (talk) 13:32, 20 November 2007 (UTC)