Tech & Buying Guide

Modern Programmable Logic Controllers manage execution through distinct operational states: Run, Stop, Start-Up, and Hold. During power-up, a controller initializes memory registers within Stop mode before briefly transitioning to Start-Up mode. During this phase, internal self-diagnostics evaluate system integrity across hardware and user programs. If the controller detects no critical faults, it enters Run mode to execute the control program continuously. However, any severe system anomaly forces the CPU back into Stop mode immediately to prevent erratic machine behavior across the plant floor.