Coded mark inversion

CMI line coding

In telecommunication, coded mark inversion (CMI) is a non-return-to-zero (NRZ) line code. It encodes zero bits as a half bit time of zero followed by a half bit time of one, and while one bits are encoded as a full bit time of a constant level. The level used for one bits alternates each time one is coded.

This is vaguely reminiscent of, but quite different from, Miller encoding, which also uses half-bit and full-bit pulses, but additionally uses the half-one/half-zero combination and arranges them so that the signal always spends at least a full bit time at a particular level before transitioning again.

CMI doubles the bitstream frequency, when compared to its simple NRZ equivalent, but allows easy and reliable clock recovery.

References

  • ITU-T G.703 (11/2001), Annex A, A.3 Definition of CMI.
  • US 4325053, Pierre Le Brozec; Francois Ferret & Pierre Doussoux, "Method and a circuit for decoding a C.M.I. encoded binary signal", issued 1982-04-13  (google patents link)

See also


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Coded Mark Inversion — El código CMI(Codec Mark Inversion) es un código en línea en banda base, cuyo objetivo al igual que otros códigos de línea es: Mínima componente continua. Máximo número de cambios de nivel Mínima frecuencia o ancho de banda para una velocidad de… …   Wikipedia Español

  • Biphase mark code — The biphase mark code is a type of encoding for binary data streams. When a binary data stream is sent without modification via a channel, there can be long series of logical ones or zeros without any transitions which makes clock recovery and… …   Wikipedia

  • CMI — • Coded Mark Inversion • Common Management Information (in TMN context) • Christina Michelsen s Institute (Norwegen) • Connection Manager Inferface (SNA) • Champaign/Urbana, IL, USA internationale Flughafen Kennung …   Acronyms

  • Line code — An example of coding a binary signal using rectangular pulse amplitude modulation with polar non return to zero code …   Wikipedia

  • Modified AMI code — Modified AMI codes are Alternate Mark Inversion (AMI) line codes in which bipolar violations may be deliberately inserted to maintain system synchronization. There are several types of modified AMI codes, used in various T carrier and E carrier… …   Wikipedia

  • Differential Manchester encoding — Differential Manchester encoding, also called biphase mark code (BMC) or FM1, is a line code in which data and clock signals are combined to form a single 2 level self synchronizing data stream. It is a differential encoding, using the presence… …   Wikipedia

  • Bipolar encoding — An example of bipolar encoding, or AMI (Alternate mark inversion). In telecommunication, bipolar encoding is a type of line code (a method of encoding digital information to make it resistant to certain forms of signal loss during transmission).… …   Wikipedia

  • Modulation — For musical change of key, see Modulation (music). For other uses, see Modulation (disambiguation). Passband modulation v · d · e …   Wikipedia

  • Manchester code — In telecommunication and data storage, Manchester code (also known as Phase Encoding, or PE) is a line code in which the encoding of each data bit has at least one transition and occupies the same time. It therefore has no DC component, and is… …   Wikipedia

  • Digital signal — Main article: Signal (electronics) A digital signal is a physical signal that is a representation of a sequence of discrete values (a quantified discrete time signal), for example of an arbitrary bit stream, or of a digitized (sampled and analog… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.