{"id":31678,"date":"2025-06-22T07:42:27","date_gmt":"2025-06-22T07:42:27","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=31678"},"modified":"2025-06-22T07:42:29","modified_gmt":"2025-06-22T07:42:29","slug":"show-the-truth-table-for-a-4-2-priority-encoder-where-the-lsb-has-the-highest-priority-as-shown-below","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/show-the-truth-table-for-a-4-2-priority-encoder-where-the-lsb-has-the-highest-priority-as-shown-below\/","title":{"rendered":"Show the truth table for a 4-2 priority encoder where the LSB has the highest priority, as shown below"},"content":{"rendered":"\n<p>Show the truth table for a 4-2 priority encoder where the LSB has the highest priority, as shown below. Note that you are allowed to use input (and output) don&#8217;t care conditions to reduce the number of rows in your truth table.<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\"><strong>The correct answer and explanation is:<\/strong><\/mark><\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Truth Table for a 4-to-2 Priority Encoder (LSB has highest priority)<\/strong><\/h3>\n\n\n\n<p>In a <strong>4-to-2 priority encoder<\/strong>, there are 4 input lines and 2 output lines. The inputs are typically labeled <strong>I3, I2, I1, I0<\/strong>, where <strong>I0<\/strong> is the least significant bit (LSB) and has the <strong>highest priority<\/strong> in this configuration. Only one output represents the position of the highest-priority active input.<\/p>\n\n\n\n<p>Here is the truth table using <strong>don\u2019t care conditions<\/strong> (<code>X<\/code>) to simplify where lower-priority inputs do not affect the output:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>I3<\/th><th>I2<\/th><th>I1<\/th><th>I0<\/th><th>Y1<\/th><th>Y0<\/th><\/tr><\/thead><tbody><tr><td>X<\/td><td>X<\/td><td>X<\/td><td>1<\/td><td>0<\/td><td>0<\/td><\/tr><tr><td>X<\/td><td>X<\/td><td>1<\/td><td>0<\/td><td>0<\/td><td>1<\/td><\/tr><tr><td>X<\/td><td>1<\/td><td>0<\/td><td>0<\/td><td>1<\/td><td>0<\/td><\/tr><tr><td>1<\/td><td>0<\/td><td>0<\/td><td>0<\/td><td>1<\/td><td>1<\/td><\/tr><tr><td>0<\/td><td>0<\/td><td>0<\/td><td>0<\/td><td>&#8211;<\/td><td>&#8211;<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Explanation (300 Words)<\/strong><\/h3>\n\n\n\n<p>A <strong>priority encoder<\/strong> assigns a binary value to the highest-priority active input. In this <strong>4-to-2 encoder<\/strong>, there are four inputs (<strong>I3, I2, I1, I0<\/strong>) and two binary outputs (<strong>Y1, Y0<\/strong>). Usually, higher input numbers (I3 being most significant) have the highest priority, but in this design, the <strong>least significant input (I0)<\/strong> has the <strong>highest priority<\/strong>.<\/p>\n\n\n\n<p>That means if <strong>I0<\/strong> is high (1), it takes precedence over all other inputs, regardless of their state. The encoder ignores higher-numbered inputs if a lower-priority input is active. If <strong>I0 = 1<\/strong>, then the output is <code>00<\/code>. If <strong>I0 = 0<\/strong> and <strong>I1 = 1<\/strong>, then I1 takes priority, and the output becomes <code>01<\/code>. Similarly, if both I0 and I1 are 0 but <strong>I2 = 1<\/strong>, the output is <code>10<\/code>. If only <strong>I3 = 1<\/strong>, then it gets priority, giving an output of <code>11<\/code>.<\/p>\n\n\n\n<p>When all inputs are zero (<code>0000<\/code>), the output is <strong>undefined or may include an additional valid signal<\/strong> like a <code>valid<\/code> or <code>enable<\/code> output to indicate whether the output is valid.<\/p>\n\n\n\n<p>To reduce the truth table size, <strong>don\u2019t care conditions (X)<\/strong> are used for inputs with lower priority once a higher-priority input is active. This simplification avoids listing all 16 possible input combinations, instead focusing only on scenarios where the highest-priority <code>1<\/code> appears.<\/p>\n\n\n\n<p>This logic helps reduce hardware complexity in digital systems by ensuring that only the most important signal is encoded at any time.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Show the truth table for a 4-2 priority encoder where the LSB has the highest priority, as shown below. Note that you are allowed to use input (and output) don&#8217;t care conditions to reduce the number of rows in your truth table. The correct answer and explanation is: Truth Table for a 4-to-2 Priority Encoder [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-31678","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31678","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=31678"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31678\/revisions"}],"predecessor-version":[{"id":31679,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/31678\/revisions\/31679"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=31678"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=31678"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=31678"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}