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6.3 Response in the Event of an Error
This section describes the response in the event of a Modbus communication error.
If the slave (this detector) judges that there is an error with a request from the master, the slave will
create an exception response message and send it to the master without processing the request.
If an exception response message is returned from the slave, the master should be capable of
checking its contents.
In the Modbus RTU (RS-485) communication, if a communication error, listed in the table below,
occurs, the slave will not return an exception response message and wait for the next request.
Error
Description
Framing error
The stop bit of the received data cannot be detected
Overrun error
In the RS-485 communication, before reading the received data from the
received data register, the next one frame of data was received
Parity error
The parity bit of the received data cannot be detected
CRC error
The error check codes (CRC values) do not match
