In the RUN mode, what does the programmable controller do with the ladder logic?

In the RUN mode, the primary function of the programmable controller is to scan the ladder logic. Scanning involves sequentially reading each rung of the ladder logic program from top to bottom and left to right, interpreting the conditions and executing the corresponding actions based on the current state of the inputs. During this process, the controller evaluates the logic to determine which outputs should be activated or deactivated, depending on the conditions that have been met. The scanning process is fundamental to how programmable controllers operate in real-time, allowing them to respond to changes in input signals and effectively control output devices.

In contrast, while interpreting can be seen as a part of the scanning process, it does not encompass the entire operation. Holding refers to maintaining the current state without executing any new actions, and processing generally implies more extensive operations that may not specifically focus on the scanning of ladder logic as the primary activity in RUN mode. Therefore, scanning accurately captures the essential function performed by the programmable controller during its RUN mode.