How is logic evaluated in a ladder logic program?

In ladder logic programs, logic is evaluated based on the actual state of the inputs and the corresponding conditions specified in the rungs of the ladder diagram. The correct choice indicates that logic execution occurs when all instructions and their corresponding tags reflect the current conditions being examined. This means that every input and condition must be verified against the physical state or value they represent.

For example, if a rung is designed to represent a condition that requires all inputs to be true for the output to activate, the logic must check that each input is indeed in the required state (such as being closed or high). If they are, then the rung is considered true, activating the output.

In contrast, other choices imply different conditions for evaluation. Evaluating logic based on at least one input being true does not accurately describe how ladder logic operates since it does not take into account the requirement for all specified conditions to be satisfied. Similarly, stating that logic is evaluated when no inputs are true or when an output is manually set does not reflect the fundamental evaluation process of ladder logic, which is based on the actual state of each instruction and tag associated with the rungs in the program. This comprehensive evaluation method ensures that control actions are only taken when all necessary conditions are appropriately met.