A programmable logic controller includes an error detection unit, a data memory storing error occurrence information indicating, for each error kind, whether the error detection unit has detected an error, an error automatic cancellation processing unit determining whether an error factor of each error has been eliminated and, when the error factor has been eliminated, performing an error cancellation process including a process to change the error occurrence information to error non-occurrence, and an error-automatic-cancellation-permission determination unit referring to an error automatic cancellation permission setting and determining, when the error detection unit detects an error, whether the error is canceled by the error automatic cancellation processing unit on the basis of the error automatic cancellation permission setting, wherein the error automatic cancellation processing unit performs the error cancellation process on the error that the error-automatic-cancellation-permission determination unit has determined that the error automatic cancellation processing unit is to cancel.

An object of the present invention is to efficiently identify an abnormal device by analyzing and classifying characteristics such as periodicity and continuity of data related to each device. A programmable logic controller collects data held by a device as a collection target out of the plurality of devices in accordance with a predetermined collection setting for each scan cycle of the user program, classifies each of the devices into one of a plurality of types on the basis of a characteristic of the collected time-series data of each of the devices, and determines a detection algorithm used in identification of the device as an abnormal device in accordance with the time-series data of the device collected by the collection section and the type of the device classified by the classification section for each of the devices.

An object of the present invention is to efficiently identify an abnormal device by analyzing and classifying characteristics such as periodicity and continuity of data related to each device. A programmable logic controller collects data held by a device as a collection target out of the plurality of devices in accordance with a predetermined collection setting for each scan cycle of the user program, classifies each of the devices into one of a plurality of types on the basis of a characteristic of the collected time-series data of each of the devices, and determines a detection algorithm used in identification of the device as an abnormal device in accordance with the time-series data of the device collected by the collection section and the type of the device classified by the classification section for each of the devices.

A monitoring device for a programmable controller includes: a display portion configured to display, on a display, a step that is being executed by the programmable controller among a plurality of steps in such a manner that the step can be distinguished from the other steps; a receiving portion configured to receive selection of a step serving as an initial point of reactivation in a case where a facility stops during a continuous operation by the programmable controller; and a change instruction generation portion configured to generate an instruction to the programmable controller so as to cause the programmable controller to restart execution of control processes from the step received by the receiving portion at the time of the reactivation.