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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Encoder (digital)</span></span>

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<p>An <b>encoder</b> (or "simple encoder") in <a href="Digital_electronics" title="Digital electronics">digital electronics</a> is a <a href="One-hot" title="One-hot">one-hot</a> to binary <a href="Code" title="Code">converter</a>. That is, if there are 2<sup><i>n</i></sup> input lines, and at most only one of them will ever be high, the binary code of this 'hot' line is produced on the <i>n</i>-bit output lines. A binary encoder is the <a href="Duality_(mathematics)" title="Duality (mathematics)">dual</a> of a <a href="Binary_decoder" title="Binary decoder">binary decoder</a>.

</p><p>If the input circuit can guarantee at most a single-active input, a simple encoder is a better choice than a <a href="Priority_encoder" title="Priority encoder">priority encoder</a>, since it requires less logic to implement. However, a simple encoder can generate an incorrect output when more than a single input is active, so a <a href="Priority_encoder" title="Priority encoder">priority encoder</a> is required in such cases.

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<div class="mw-heading mw-heading2"><h2 id="Types_of_encoder">Types of encoder</h2></div>

<div class="mw-heading mw-heading3"><h3 id="2n-to-n_encoders">2<sup>n</sup>-to-n encoders</h3></div>

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<annotation encoding="application/x-tex">{\displaystyle 2^{n}}</annotation>

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</math></span><img src="./8226f30650ee4fe4e640c6d2798127e80e9c160d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.381ex; height:2.343ex;" alt="{\displaystyle 2^{n}}" loading="lazy"></span>-to-n encoder has n number of outputs in correspondence to the <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 2^{n}}">

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<annotation encoding="application/x-tex">{\displaystyle 2^{n}}</annotation>

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</math></span><img src="./8226f30650ee4fe4e640c6d2798127e80e9c160d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.381ex; height:2.343ex;" alt="{\displaystyle 2^{n}}" loading="lazy"></span> number of inputs. It thus reduces the number of transmission lines and can be compared to a <a href="Multiplexer" title="Multiplexer">multiplexer</a>. Only one of the inputs become "high" (logic state "1") at a time.

</p><p>For example, a 4-to-2 simple encoder takes 4 input bits and produces 2 output bits. The illustrated gate level example implements the simple encoder defined by the truth table, but it must be understood that for all the non-explicitly defined input combinations (i.e., inputs containing 0, 2, 3, or 4 high bits) the outputs are treated as <a href="Don't-care_term" title="Don't-care term">don't cares</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading4"><h4 id="4-to-2_encoder">4-to-2 encoder</h4></div>

<caption>Truth Table

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<td colspan="4">Input</td>

<td colspan="3" style="border-left:2px solid #000;">Output

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