Which condition must be true for the DN bit to be set in a counter instruction?

The condition for the DN (Done) bit to be set in a counter instruction is that the accumulated value must meet or exceed the preset. This means that the counter has successfully counted the number of occurrences or events specified by its preset value. When the accumulated count reaches or exceeds this value, it indicates that the counter has completed its intended function, and at this point, the DN bit is activated to signal that the operation is complete.

This aspect of counter functionality is crucial in programming and automation, as it allows for accurate timing and event tracking. Understanding this condition enables programmers to effectively employ counters in control systems to monitor processes and provide feedback based on event counting. The ability to recognize when a counter has reached its preset allows for further actions or state changes in a control logic sequence, facilitating robust automation operations.