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Modbus/Tcp - Mitsubishi Electric A800-E Instruction Manual

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2.5.5

Modbus/TCP

The Modbus/TCP protocol allows transmission of Modbus messages via Ethernet communication.
Communication specifications
• The communication specifications are given below.
Item
Communication protocol
Conforming standard
Waiting time setting
Maximum number of connections
Slave function
Number of simultaneously
(server)
acceptable request messages
Initial setting
• 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
21.)
• 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
• 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
25.)
Message format

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.)
• Query
A message is sent to the slave (the inverter) having the address specified by the master.
• 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.
• 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.
(N) Operation via communication and its settings
Description
Modbus/TCP protocol
Open Modbus/TCP specification
Not used
3
1
page
24.)
Request
Response
Within 10 ms∗1
39
PARAMETER
2
GROUP
N

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