Chapter 4 Explanation of Functions
4-132
Message configuration: Response
(i) Time required for communication
After the inverter receives a query, the inverter waits for the sum of the silent interval (corresponding to the
transmission of 3.5 characters) and the communication wait time (C078) before sending a response.
After receiving a response from the inverter, the master system must wait for the silent interval (corresponding to
the transmission of 3.5 characters) or longer before sending the next query to the inverter.
(ii) Normal response
If the query specifies the function code (08h) for the loopback test, the inverter returns a response that has the
same contents as the query.
If the query specifies a function code (05h, 06h, 0Fh, or 10h) for writing data to registers or coils, the inverter
returns the query without a change as a response.
If the query specifies a function code (01h or 03h) for reading a register or coil, the inverter returns a response
that contains the slave address and function code specified in the query and the data read from the register or
coil.
(iii) Response upon error
Field configuration
If the query includes an error (other than a communication error), the inverter returns an exception response
without executing the function specified by the query.
To know the error, check the function code set in the exception response. The exception response in reply to a
query includes a function code that is the sum of "80h" and the function code specified by the query.
The exception code in the exception response indicates the content of the error.
Exception codes
An unsupported function is specified.
The specified address is not found.
The specified data has an unacceptable format.
The data to be written to a register exceeds the range of inverter specifications.
The inverter restricts the execution of the specified function:
- Rewriting a register that cannot be rewritten during the operation
- Issuing an Enter command during the operation (in undervoltage status)
- Writing to a register during tripping (because of undervoltage)
- Writing to a read-only register (coil)
(iv) No response
The inverter ignores a query without returning any response if:
- the query is a broadcast query,
- a communication occurs during the reception of the query,
- the slave address specified in the query differs from that of the inverter,
- the time interval between data items in the query message is less than the time corresponding to the
transmission of 3.5 characters, or
- the data length of the query is invalid.
Note: In the master system, set a timer to monitor the responses from the inverter, and configure the master system
so that, when the inverter does not return the response to a query within a specified limit time, the master
system resends the query.
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