Mitsubishi Electric FR-A820-00046 (0.4K), Instruction Manual

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Ethernet communication (FR-A800-E) Parameters
5 - 786
5.22.2 Modbus®/TCP
The Modbus®/TCP protocol allows transmission of Modbus® messages via Ethernet communication.
Communication specifications
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The Modbus®/TCP communication specifications are given below.
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Initial setting
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To select Modbus®/TCP for the application, set "502" in any of Pr. 1427 to Pr. 1429 (Ethernet
function selection 1 to 3). (Refer to page 5-677.)
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To limit the network devices that send the operation or speed command through the Ethernet
network (Modbus®/TCP), set the range of IP addresses (Pr. 1449 to Pr. 1454). (Refer to page 5-681.)
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Set the interval of the communication check (signal loss detection) time in Pr. 1432 "Ethernet
communication check time interval" for all devices with IP addresses in the range specified for
Ethernet command source selection (Pr. 1449 to Pr. 1454). (Refer to page 5-682.)
Message format
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Query
A message is sent to the slave (the inverter) having the address specified by the master.
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Normal response
After the query from the master is received, the slave executes the request function, and returns
the corresponding normal response to the master.
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Error response
When an invalid function code, address or data is received by the slave, the error response is
returned to the master.
This response is appended with an error code that indicates the reason why the request from the
master could not be executed.
This response cannot be returned for errors, detected by the hardware, frame error and header
check error.
Item Description
Communication protocol Modbus®/TCP protocol
Conforming standard Open Modbus®/TCP specification
Waiting time setting Not used
Maximum number of connections 3
Slave function (server)
Number of simultaneously acceptable
request messages
1
Tab. 5-367: Modbus®/TCP communication specifications
I003124E
Fig. 5-388: Message format
Request
Response
Within 10 ms
The chart shows the performance when the inverter is connected to a master on a 1:1 basis. (It takes 10 ms or
more for parameter clear, all parameter clear, or accessing multiple registers.)