Editing Programmable logic controller (section)

== Safety PLCs ==
Safety PLCs can be either a standalone device or a [[Safety integrity level|safety-rated]] hardware and functionality added to existing controller architectures ([[Allen-Bradley]] GuardLogix, [[Siemens]] F-series, etc.). These differ from conventional PLC types by being suitable for safety-critical applications for which PLCs have traditionally been supplemented with hard-wired [[safety relay]]s and areas of the memory dedicated to the safety instructions. The standard of safety level is the [[Safety integrity level|SIL]]. 

A safety PLC might be used to control access to a [[Industrial robot|robot cell]] with [[Trapped-key interlocking|trapped-key access]], or to manage the shutdown response to an emergency stop button on a conveyor production line. Such PLCs typically have a restricted regular instruction set augmented with safety-specific instructions designed to interface with emergency stop buttons, light screens, and other safety-related devices. 

The flexibility that such systems offer has resulted in rapid growth of demand for these controllers.{{Citation needed|date=July 2022}}