7 Serial interface (Modbus RTU)
7.3 Operating mode Modbus RTU
146 DC1 Frequency Inverter 10/12 MN04020003Z-EN www.eaton.com
7.3.2 Structure of the slave response
7.3.2.1 Required transfer time
• The time between receiving a request from the master and the response
of the frequency inverter is at least 3.5 characters (rest time).
• Once the master has received a response from the frequency inverter, it
must wait for at least the rest time before it can send a new request.
7.3.2.2 Normal slave response
• If the master request contains a write register function (function code
06), the frequency inverter immediately returns the request as a
response.
• If the master request contains a read register function (function code
03), the frequency inverter returns the read data with the slave address
and the function code as a response.
7.3.2.3 No slave response
In the following cases, the frequency inverter ignores the request and does
not send a reply:
• on receiving a broadcast request.
• if the request contains a transmission error.
• If the slave address in the request does not match the frequency
inverter's address.
• With a CRC or parity error.
• If the time interval between the messages is less
than 3.5. characters.
￫
The master must be programmed to repeat the request if it
does not receive a response within a specified time.
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