Exception response by server

In operating mode MODBUS client, the AC500 does only send requests, if the parameters at the MODMAST inputs are logically correct. Nevertheless, it can happen that a server cannot process the request of the client or that the server cannot interpret the request due to transmission errors or in case it’s capabilities are exceeded in any way. In those cases, the server returns an exception response to the client. In order to identify this response as an exception response, the function code returned by the server is a logical OR interconnection of the function code received from the client and the value 80HEX.

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• Example