Chapter 11 RS485 Communication
11-1-7
■ (5) Communication time required
The response of the inverter after the inverter receives a query is as follows: "Silent interval (3.5
characters)" + "Communication wait time [C078]" + "Processing time such as response message
creation (several msec)".
After the external control equipment receives a response from the inverter, be sure to leave an
interval of at least the silent interval (3.5 characters) between sending the next query.
■ (6) Normal response
Returns the response according to the per-query formats described in "11.2 Explanation of
Modbus-RTU Function Codes".
■ (7) Abnormal response
If there is a fault (excluding communication error) in the contents of the query, the inverter
returns an exceptional response without executing anything.
To determine the error, check the function code of the response. The function code of the
exceptional response is the value added by 80h to the function code of the query.
For error details, see section "11.2.9 Exceptional Responses".
Exceptional Response Field Configuration
■ (8) No response
In the following cases, the inverter ignores the query and returns no response.
A broadcast (a query with a slave address "0") is received.
A communication error is detected during query reception.
The slave address of the query does not match the inverter setting slave address.
The time interval between the data composing the message is 3.5 characters or less.
The query data length is invalid.
The frame reception interval exceeds 1.5 characters.
The error check code of the query does not match (CRC error).
A group-wide broadcast (a query with a slave address between 250 and 254) is received.
In the external control equipment, provide a timer to monitor the response message from the
inverter. If no response message is returned within a specific time, provide retransmission
processing or error processing, such as sending the same query again.
To Next Page
Loading...
