A slave (51, 61), comprising: a volatile storage section connected to a control section; a non-volatile storage section connected to the control section, characterized in that the slave further comprises: a communication interface connected to a master in an industrial network; and the control section configured to perform processing based on control data transmitted from the master via the communication interface; wherein the control section is further configured to perform - first storage processing storing log information into the volatile storage section during normal operation before a communication abnormality occurs such that communication with the master cannot be kept, - communication abnormality determination processing for determining whether the communication abnormality has occurred, and - second storage processing storing the log information into the non-volatile storage section by acquiring the log information from the volatile storage section, in response to a determination made in that the communication abnormality has occurred as a result of the communication abnormality determination processing wherein in the first storage processing, the control section is configured to associate information, relating to the control data transmitted from the master, with a time of performing the processing based on the control data, and to store the associated information into the volatile storage section as the log information. a volatile storage section connected to a control section; a non-volatile storage section connected to the control section, characterized in that the slave further comprises: a communication interface connected to a master in an industrial network; and the control section configured to perform processing based on control data transmitted from the master via the communication interface; wherein the control section is further configured to perform - first storage processing storing log information into the volatile storage section during normal operation before a communication abnormality occurs such that communication with the master cannot be kept, - communication abnormality determination processing for determining whether the communication abnormality has occurred, and - second storage processing storing the log information into the non-volatile storage section by acquiring the log information from the volatile storage section, in response to a determination made in that the communication abnormality has occurred as a result of the communication abnormality determination processing wherein in the first storage processing, the control section is configured to associate information, relating to the control data transmitted from the master, with a time of performing the processing based on the control data, and to store the associated information into the volatile storage section as the log information. a communication interface connected to a master in an industrial network; and the control section configured to perform processing based on control data transmitted from the master via the communication interface; wherein the control section is further configured to perform - first storage processing storing log information into the volatile storage section during normal operation before a communication abnormality occurs such that communication with the master cannot be kept, - communication abnormality determination processing for determining whether the communication abnormality has occurred, and - second storage processing storing the log information into the non-volatile storage section by acquiring the log information from the volatile storage section, in response to a determination made in that the communication abnormality has occurred as a result of the communication abnormality determination processing - first storage processing storing log information into the volatile storage section during normal operation before a communication abnormality occurs such that communication with the master cannot be kept, - communication abnormality determination processing for determining whether the communication abnormality has occurred, and - second storage processing storing the log information into the non-volatile storage section by acquiring the log information from the volatile storage section, in response to a determination made in that the communication abnormality has occurred as a result of the communication abnormality determination processing wherein in the first storage processing, the control section is configured to associate information, relating to the control data transmitted from the master, with a time of performing the processing based on the control data, and to store the associated information into the volatile storage section as the log information.