1

An 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; and

function of holding the data monitored with the protocol monitor function in advance when abnormality is detected by the abnormality diagnosis function.

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2

The controller according to Claim 1, further comprising a ring buffer, and whereinthe data communicated with the device adopts a communication method of once being stored in the ring buffer;

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.

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3

The controller according to Claim 1, wherein the controller corresponds to Ethernet (registered trademark) or EtherCAT (registered trademark).

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4

The controller according to Claim 2, wherein the controller corresponds to Ethernet (registered trademark) or EtherCAT (registered trademark); andthe ring buffer is set in an Ethernet driver unit.

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