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{{Use dmy dates|date=August 2019|cs1-dates=y}}
'''Inversion encoding''' is an encoding technique used for [[Bus encoding|encoding bus transmissions]] for low power systems. It is based on the fact that a large amount of power is wasted because of transitions, especially in external buses, and thus reducing these transitions aids optimization of [[power dissipation]]. This is done introducing an additional signal line named INV to the bus lines. This signal determines whether the other lines should be inverted or not.
== Overview ==
The bus-invert encoding technique uses an extra signal (INV) to indicate the "polarity" of the data. Having a bus-invert code word INV@x where @ is the concatenation operator and x denotes either the source word or its [[ones' complement]], the bus-invert decoder takes the code word and produces the corresponding source word. If the INV signal is 1, the result is
=== Usage scenarios===
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== Performance analysis ==
The bus-invert method generates a code that has the property that the maximum number of transitions per time-slot is reduced from n to n/2+1 and thus the peak power dissipation for [[input/output]] (I/O) is reduced by nearly the half. From the [[coding theory]] point of view, the bus-invert code is a time-dependent Markovian code.
While the maximum number of transitions is reduced by half, the average number has a smaller decrease. For an 8-bit bus for example, the average number of transitions, using bus-invert coding becomes 3.27 (instead of 4), or 0.41 (instead of 0.5) transitions per bus-line per time-slot. This means that the average number of transitions is 81.8% of the number with an unencoded bus. This is because the invert line contributes some transitions and the distribution of the Hamming distances is not uniform.<ref name="Stan_1995"/>
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== References ==
{{Reflist|refs=
<ref name="Stan_1995">{{cite journal |author-first1=Mircea R. |author-last1=Stan |author-first2=Wayne P. |author-last2=Burleson |title=Bus-Invert Coding for Low-Power I/O |journal=IEEE Transactions
}}
==Further reading==
* {{cite book |author-first=Vincent C. |author-last=Gaudet |chapter=Chapter 4.1. Low-Power Design Techniques for State-of-the-Art CMOS Technologies |editor-first=Bernd |editor-last=Steinbach |editor-link=:de:Bernd Steinbach |title=Recent Progress in the Boolean Domain |publisher=[[Cambridge Scholars Publishing]] |
[[Category:Electronics optimization]]
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