EET-123 Study Guide - Final Guide: Switch, Humber College, The Sixteen
Document Summary
When a plc is set in the run mode, the processor reads in data from the input module and stores the values in memory. A portion of the memory is reserved for inputs. One register in the input data table part of memory is called a word. One word is made up of 16 bits. Each word has a unique address, eg. i:1. Each bit in a word has a unique address, eg. i:1/00, or i:1/13 etc. For example if the input card in slot 1 has sixteen screw terminals. Input card 1 is represented by word i:1. The sixteen inputs are represented by the sixteen bits in word i:1, from 00 to 15. When the plc reads data from the input module, it stores the status of each input as bit zero or bit one in the appropriate word and bit location. Each bit in word i:1 represents the status of the toggle switch or the pushbutton.
