📑 Table of Contents▼
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.

The CMI patent was filed in 1979 with a priority date of July 27, 1978.[1] It is similar to the Quick CUTS scheme published by Bob Cottis and Mike Blandford in the Amateur Computer Club newsletter in August 1978.[2]

See also

edit

References

edit
  1. ^ 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 
  2. ^ "A High Speed CUTS Casette Interface" (PDF). Amateur Computer Club Newsletter. 6 (3). August 1978. Archived from the original (PDF) on 2015-07-21. Retrieved September 29, 2022.
  • ITU-T G.703 (11/2001), Annex A, A.3. Definition of CMI.
edit
  • Wikimedia Commons logo Media related to Coded mark inversion at Wikimedia Commons


Stub icon

This computer science article is a stub. You can help Wikipedia by adding missing information.

📚 Artikel Terkait di Wikipedia

Line code

inversion, Differential Manchester encoding, coded mark inversion and Miller encoding. differential coding each symbol relative to the previous symbol

Differential Manchester encoding

Other line codes with this property include NRZI, bipolar encoding, coded mark inversion, and MLT-3 encoding. If the high and low signal levels have the same

Bipolar encoding

bipolar encoding is a paired disparity code, of which the simplest example is alternate mark inversion. In this code, a binary 0 is encoded as zero volts

Differential coding

NRZI, biphase mark code, coded mark inversion, and MLT-3 encoding. A method illustrated above can deal with a data stream inversion (it is called 180°

Manchester code

Transitions at the start of a period are overhead and don't signify data. Coded mark inversion Differential Manchester encoding Binary offset carrier modulation

CMI

audio workstation introduced in 1979 by Fairlight Coded mark inversion, a non-return-to-zero (NRZ) line code Content Management Interface, an Open Mobile Alliance

On–off keying

It is analogous to unipolar encoding line code. On–off keying is most commonly used to transmit Morse code over radio frequencies (referred to as CW (continuous

Kansas City standard

Published in 1978, it predates the 1982 patent for the similar coded mark inversion proposal (but not its priority date of July 27, 1978). Acorn Computers