Programmable logic controller, setting tool, and recording medium

A programmable logic controller for cyclically executing a control program, the programmable logic controller comprising:

• a differential logging circuit to collect, from a device storage to store device values including an input value and an output value for the control program, a device value that has changed among device values set as collection targets from the device values in the device storage at each execution of the control program, and to store a differential log being a log of the collected device value into a differential log storage;
• a collective logging circuit to collect a determined number of data pieces at a time, from the device storage, for the device values set as collection targets from the device values in the device storage at a set time as reference data to be used to collect the differential log, and to collectively store logs of the collected device values into a reference data storage;
• and
• a split logging circuit to acquire as split logs, after the set time, logs of the device values multiple times, and to store the split logs into the reference data storage,
• wherein
• the split logging circuit stores the split logs into the reference data storage multiple times to store new reference data into the reference data storage,
• after the new reference data is stored into the reference data storage, the differential logging circuit overwrites a differential log that was stored in the differential log storage prior to generation of the new reference data with a new differential log corresponding to the new reference data, and
• the split logging circuit determines the number of data pieces for device values collected at a time based on a set N value and a number of data pieces for device values stored in the device storage and a data size of each of the data pieces for the device values.