Patent ID: 8457003

Claim:
A Factory Automation (FA) controller comprising: abnormality diagnosis function of determining presence of abnormality of a network to be connected; protocol monitor function of monitoring data communicated with a device connected to the network; function of holding the data monitored with the protocol monitor function in advance when abnormality is detected by the abnormality diagnosis function; and a ring buffer, and wherein the controller is further configured so that the data communicated with the device causes adoption of a communication method of initially being stored in the ring buffer; wherein the data held in the ring buffer is used as monitor data and, when abnormality is detected by the abnormality diagnosis function, data immediately before the abnormality detection is held, and a communication after the abnormality is detected is continued using a region other than a region holding the data immediately before the abnormality detection in the ring buffer, wherein the region within the ring buffer that is used after the abnormality is detected is defined by a capture stop pointer and a capture head data pointer, wherein the capture stop pointer is a position within the ring buffer where a next reception or transmission data is to be stored after the abnormality is detected, the capture head pointer being a position within the ring buffer that is next to a buffer portion within the ring buffer, in which the capture head pointer differs from the capture stop pointer by a pointer value corresponding to the buffer portion that is used for general communication when the abnormality is detected, wherein the ring buffer includes a reception ring buffer and a transmission ring buffer, and wherein the capture head pointer and the capture stop pointer of the reception ring buffer differ in respective values from the capture head pointer and the capture stop pointer of the transmission ring buffer.