A counter's done (DN) bit is triggered when the accumulated value meets or exceeds what?

A counter's done (DN) bit is triggered when the accumulated value meets or exceeds the preset value. The preset value is a specific number that is set at the beginning of the counting process, indicating the target or threshold that the counter needs to reach for the done bit to activate. Once the accumulated value, which represents the total count of events or signals, equals or surpasses this preset value, it signifies that the counter has completed its intended task, prompting the done bit to be set.

This function is crucial in programmable controller systems as it allows for conditional operations to follow the completion of a counting process, enabling automation tasks such as starting other functions, logging events, or triggering alarms. Understanding the role of the preset value in the operation of counters is vital for effectively utilizing programmable controllers in a variety of applications.