What does "firmware" refer to in a PLC?

Firmware in the context of a PLC refers to software that is embedded into the hardware of the device itself. This type of software is critical because it provides the foundational control and functionality necessary for the PLC to execute its primary tasks. Unlike traditional software that can be easily replaced or modified by the user, firmware is closely integrated with the hardware and is typically designed to manage and control specific operations of the device. It remains in a read-only memory (ROM) or flash memory and ensures that the PLC can boot up and run effectively.

The importance of firmware lies in its role in establishing the basic operating system and control logic that supports the PLC's functionality. This includes processes such as scanning inputs, executing control logic, and updating outputs, which are essential for automated control tasks in industrial settings. Since firmware is built specifically for the PLC hardware, it is often optimized for performance, reliability, and resource utilization, making it a crucial component of any PLC system.