Programmable logic controller, sequence control system, and non-transitory computer readable medium

A non-transitory computer readable medium storing an active state control program for a programmable logic controller to execute a sequence program, the sequence program including a first execution element defining a preceding action, a second execution element defining a subsequent action to be performed subsequently to the preceding action, and a transition condition element defining a transition condition for transition of an active state from the first execution element to the second execution element, the active state control program causing the programmable logic controller to function as:

• a flag data update receiver to receive an update of flag data indicating whether activation of the second element is permitted or prohibited;
• an interrupt receiver to receive an interrupt instruction indicating a request for activating the second execution element independently of whether the transition condition is satisfied;
• an interrupt preventer to refer to latest flag data when the interrupt receiver receives the interrupt instruction, and to maintain, when the flag data indicates that the activation of the second execution element is prohibited, an inactive state of the second execution element and output an interrupt invalidation error indicating that the interrupt instruction is invalidated;
• and
• an executor to activate the second execution element when the interrupt receiver receives the interrupt instruction and the latest flag data indicates that the activation of the second execution element is permitted.