[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-seo-655295-105":3,"detail-sidebar-cat-0-en-105":81,"doc-detail-655295-en":130},{"code":4,"msg":5,"data":6},0,"ok",{"site_id":7,"language":8,"slug":9,"title":10,"keywords":11,"description":12,"schema_data":13,"social_meta":74,"head_meta":76,"extra_data":78,"updated_unix":80},105,"en","ladder-logic-fundamentals","Ladder Logic Fundamentals","","Ladder Logic Fundamentals introduces PLC ladder logic as the dominant method for programming industrial controllers, emphasizing that inputs and ladder rungs evaluate to TRUE or FALSE. The material explains how rung structure places input instructions on the left and outputs on the right, and how processor scanning order affects control flow when jumps or subroutines execute. It also covers core logic functions (AND, OR, XOR), then contrasts logical continuity with electrical continuity to clarify when outputs energize.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/technology/","Technology",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/ladder-logic-fundamentals/655295/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/ladder-logic-fundamentals/655295.png","ImageObject",300,407,{"name":42,"@type":43},"นรินทร์","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-11-01","2026-10-25",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",6,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"What makes ladder logic rungs evaluate to TRUE or FALSE?","Question",{"text":63,"@type":64},"PLC programs treat inputs and ladder rungs as logical states. When required input conditions are TRUE, the rung becomes TRUE and energizes the corresponding output action.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"Where are input and output instructions located in a ladder program rung?",{"text":68,"@type":64},"Input instructions are entered on the left side of the rung, while output instructions are entered on the right side. Power rails simulate the supply lines.",{"name":70,"@type":61,"acceptedAnswer":71},"How does logical continuity differ from electrical continuity?",{"text":72,"@type":64},"Logical continuity exists when there is a continuous path of TRUE conditions from the left power rail to the output instruction(s), causing the rung to become true. Electrical continuity refers to a complete current path in the input circuit, setting a bit in the PLC memory (input image table) to 1.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},655295,1793051838,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,104,109,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":89,"show_sort_weight":90,"slug":91},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":93,"show_sort_weight":94,"slug":95},"Exam",70,"exam",{"id":97,"doc_module":4,"doc_module_name":25,"category_name":98,"show_sort_weight":99,"slug":100},5,"Comic",60,"comic",{"id":55,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":102,"slug":103},50,"technology",{"id":105,"doc_module":4,"doc_module_name":25,"category_name":106,"show_sort_weight":107,"slug":108},7,"Healthcare",40,"healthcare",{"id":110,"doc_module":4,"doc_module_name":25,"category_name":111,"show_sort_weight":112,"slug":113},8,"Research & Report",30,"research-report",{"id":115,"doc_module":4,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},9,"Religion & Spirituality",20,"religion-spirituality",{"id":117,"doc_module":4,"doc_module_name":25,"category_name":120,"show_sort_weight":117,"slug":121},"World Cup","world-cup",{"id":123,"doc_module":4,"doc_module_name":25,"category_name":124,"show_sort_weight":123,"slug":125},10,"Lifestyle","lifestyle",{"id":127,"doc_module":4,"doc_module_name":25,"category_name":128,"show_sort_weight":97,"slug":129},19,"General","general",{"code":4,"msg":82,"data":131},{"doc_id":79,"user_id":132,"nickname":42,"user_avatar":133,"doc_module":4,"category_id":55,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":139,"language":140,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":12,"update_tm":144,"read_time":145},2336475104957,"https://ap-avatar.wpscdn.com/avatar/22000c4c6bd8a5076e1?x-image-process=image/resize,m_fixed,w_180,h_180&k=1787554080175789136","MET 382 1/14/2008  \nPLC Fundamentals –  \nLadder Logic Fundamentals  \nMET 382  \nControls & Instrumentation for Automation  \nSpring ‘08  \nT. E. Kostek  \nTopics  \n􀂄 PLC programming languages  \n􀂄 Anatomy of a ladder program  \n􀂄 Logic functions  \n􀂄 Logical continuity vs. electrical continuity  \n􀂄 I/O Mapping  \n􀂄 Mastering examine on and examine off instructions  \n􀂄 The PLC scanning process  \n2  \nLadder Logic Fundamentals 1  \nMET 382 1/14/2008  \nPLC Programming Languages  \n􀂄 In the United States, ladder logic is the most popular method used to program a PLC  \n􀂄 This course will focus primarily on ladder logic programming  \n􀂄 Other programming methods include:  \n􀂅 Function block diagrams (FBDs)  \n􀂅 Structured text (ST)  \n􀂅 Instruction List (IL)  \n􀂅 Sequential function charts (SFCs)  \n3  \n\n| Anatomy of a Ladder Program\u003Cbr>| 4 |\n| --- | --- |\n\nLadder Logic Fundamentals 2  \nMET 382 1/14/2008  \nAnatomy of a Ladder Program (cont’d)  \n􀂄 Input instructions are entered on the left  \n􀂄 Output instructions are entered on the right  \n􀂄 The power rails simulate the power supply lines  \n􀂅 L1 and L2 for AC circuits and +24 v and ground for DC circuits  \n􀂄 Most PLCs allow more than one output per rung  \n5  \nAnatomy of a Ladder Program (cont’d)  \n􀂄 The processor (or “controller”) scans ladder rungs from top-to-bottom and from left-to-right.  \n􀂅 The basic sequence is altered whenever jump or subroutine instructions are executed.  \n6  \nLadder Logic Fundamentals 3  \nMET 382 1/14/2008  \nAnatomy of a Ladder Program (cont’d)  \nA 3-rung example ladder program  \nAnatomy of a Ladder Program (cont’d)  \nRung Comment  \nRung Number  \nDescription assigned to alias tag Alias tag pointing to base address Base address  \nInput Instruction  \n8  \nLadder Logic Fundamentals 4  \nMET 382 1/14/2008  \nLogic Functions  \n􀂄 PLC programming is a logical procedure  \n􀂄 In a PLC program,“things”(inputs and rungs) are either TRUE or FALSE  \n􀂄 If the proper input conditions are TRUE:  \n􀂅 The rung becomes TRUE and an output action occurs (for example, a motor turns on)  \n􀂄 If the proper input conditions are not TRUE:  \n􀂅 The rung becomes FALSE and an output action does not occur  \n9  \nLogic Functions (cont’d)  \n􀂄 Ladder logic is based on the following logic functions:  \n􀂅 AND  \n􀂅 OR  \n􀂄 Sometimes called “inclusive OR”  \n􀂅 Exclusive OR  \n10  \nLadder Logic Fundamentals 5  \nMET 382 1/14/2008  \n\n| Logic Functions-AND\u003Cbr>|  |  |  |  |  |  |  |  |\n| --- | --- | --- | --- | --- | --- | --- | --- | --- |\n| Input 1\u003Cbr>Input 2 |  | |  |  |  | Output |  |  |\n| Input 1 Input 2 Output 0 0 0 0 1 0 1 0 0 1 1 1 |  |  |  |  |  |  | 0 Æ False\u003Cbr>1 Æ True |  |\n| Contacts ANDed together | |  | | | ( )~~ ~~ |  |  | 11 |\n\n\n| Logic Functions-OR\u003Cbr>|  |  |  |\n| --- | --- | --- | --- |\n| Input 1\u003Cbr>Input 2 | | Output |  |\n| Input 1 Input 2 Output 0 0 0 0 1 1 1 0 1 1 1 1 |  |  | 0 Æ False\u003Cbr>1 Æ True |\n| Contacts ORed together\u003Cbr>\u003Cbr>\u003Cbr>\u003Cbr>12 |  |  |  |\n\nLadder Logic Fundamentals 6  \nMET 382 1/14/2008  \n\n| Logic Functions-Exclusive OR\u003Cbr>In addition to ANDing and ORing, the Exclusive OR (XOR) is also useful. When the inputs are DIFFERENT, the XOR output is true.\u003Cbr>|  |  |  |\n| --- | --- | --- | --- |\n| Input 1\u003Cbr>Input 2 | \u003Cbr>XOR\u003Cbr>Logic | Output |  |\n| Input 1 Input 2 Output 0 0 0 0 1 1 1 0 1 1 1 0 |  |  | 0 Æ False\u003Cbr>1 Æ True |\n| 13 |  |  |  |\n\nLogic Functions (cont’d)  \n􀂄 Example 1 – Inputs ANDed together in series  \nInputs Output  \nThree input instructionsANDed together.  \nAll 3 input instructions must be  \ntrue in order to energize the output  \n14  \nLadder Logic Fundamentals 7  \nMET 382 1/14/2008  \nLogic Functions (cont’d)  \n􀂄 Example 2 – Inputs ORed together in parallel Inputs  Output   \nThree input instructions ORed together.  \nIf any of the 3 input instructions are  \ntrue the output will be energized 15  \nLogic Functions (cont’d)  \n􀂄 Example 3 – A combination of ANDing and ORing  \n16  \nLadder Logic Fundamentals 8  \nMET 382 1/14/2008  \nLogical Continuity  \n􀂄 Logical continuity in a ladder rung occ","cbCaiad8NK8xk2K2","https://ap.wps.com/l/cbCaiad8NK8xk2K2","pdf",257406,27,"English","# PLC Programming Languages\n# Anatomy of a Ladder Program\n## Input and Output Placement\n## Processor Scanning Behavior\n# Logic Functions\n## AND\n## OR\n## Exclusive OR (XOR)\n# Logical Continuity\n## Logical Continuity vs. Electrical Continuity","[{\"question\":\"What makes ladder logic rungs evaluate to TRUE or FALSE?\",\"answer\":\"PLC programs treat inputs and ladder rungs as logical states. When required input conditions are TRUE, the rung becomes TRUE and energizes the corresponding output action.\"},{\"question\":\"Where are input and output instructions located in a ladder program rung?\",\"answer\":\"Input instructions are entered on the left side of the rung, while output instructions are entered on the right side. Power rails simulate the supply lines.\"},{\"question\":\"How does logical continuity differ from electrical continuity?\",\"answer\":\"Logical continuity exists when there is a continuous path of TRUE conditions from the left power rail to the output instruction(s), causing the rung to become true. Electrical continuity refers to a complete current path in the input circuit, setting a bit in the PLC memory (input image table) to 1.\"}]","Ladder Logic Fundamentals | PDF",1792960665,68]