When are configuration settings sent to PLC-controlled devices?

The correct answer highlights that configuration settings for PLC-controlled devices are typically sent during the power-up process of the PLC system. This is essential because, at startup, the PLC initializes its operating environment, loading necessary configurations to ensure that all devices connected to it can operate under the defined parameters from the very beginning.

When the system powers up, it scans the inputs, initializes the outputs, and applies any pre-defined configuration settings to adapt to the current operational state. This ensures that the devices will function correctly and integrate seamlessly into the broader control system.

While it might seem beneficial to send configuration settings at various times, like when a sensor detects an object or at regular intervals, those approaches do not align with standard operational practices for PLCs. Additionally, sending configurations only during maintenance schedules would lead to unnecessary downtimes and could prevent the system from being optimized during regular operation. Thus, sending configurations at power-up allows for a stable and consistent operational state from the outset.