Mitsubishi Electric MELSERVO-JE MR-JE-C, Инструкция по эксплуатации

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2. MODBUS/TCP PROTOCOL
2 - 10
2.3.5 Processing at occurrence of an error
In Modbus/TCP communication, when the Query Message sent from the client (controller) includes an
incorrect value, the server (servo amplifier) returns an exception response to the client (controller).
If an error is detected in the TCP/IP layer, the server (servo amplifier) returns no message to the client
(controller).
When an exception response occurs, a value obtained by adding "80h" to the function code sent in the
Query Message is returned with an exception code.
However, no exception response occurs in the following cases.
Function code "03h" (Read Holding Registers)
When data can be read from even one of consecutive registers, no exception response occurs. In this
case, "0" is returned to the register data that cannot be read.
Function code "10h" (Preset Multiple Registers)
When data can be written into even one of consecutive registers, no exception response occurs.
Response Message
Transaction
Identifier
Protocol
Identifier
Length Field
Unit
Identifier
Function
Exception
Code
16 bits 0000h 0003h FFh 8 bits 8 bits
Message field Size Description
Transaction Identifier
(Transaction identifier) 16 bits Transaction Identifier received from the client (controller) is copied and returned.
Protocol Identifier
(Protocol identifier) 16 bits The value "0000h" is returned.
Length Field (Message length) 16 bits The byte length from Unit Identifier to Data is returned.
Unit Identifier (Unit identifier) 8 bits Unit Identifier received from the client (controller) is copied and returned.
Function (Function field) 8 bits A value obtained by adding "80h" to the function code of the Query Message is
returned.
When Function is "03h": "83h"
When Function is "08h": "88h"
When Function is "10h": "90h"
When an unsupported Function (example: "01h") is used, "Fu 80h"
(example: "81h") is returned.
Exception Code (Exception code) 8 bits An exception code is set. For details of exception codes, refer to the following
"List of exception codes".
List of exception codes
Code Error name Description
01h ILLEGAL FUNCTION
(Illegal function code)
The Query Message sent from the client set a function code that the server does not
support.
02h ILLEGAL DATA ADDRESS
(Illegal address)
The Query Message sent from the client set a register address that the server does not
support. (Ex: No register address is set, or reading or writing data from/to registers is
not available.)
03h ILLEGAL DATA VALUE
(Illegal data)
The Query Message sent from the client set data that the register cannot handle. (Ex: A
value out of the setting range is set, or "0" is set to No. of Registers.)