4P642495-1A
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2022.02
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(4) Exception response
In case the query message is faulty, the
Modbus Interface DIII
will reply an exception response. In normal
conditions the function code of the response message is the same as the query message. But in case of an
error, 0x80 is added to the function code of the response message.
The exception response includes the exception code, indicating the cause of the error.
Exception code
Name
Cause
0x01
Illegal function
This function code is not supported.
0x02
Illegal data address
Access was attempted to an unassigned register
address.
0x03
Illegal data
This query includes unauthorized data.
[Example of exception response]
In the case of setting an illegal mode to the holding register address 42002.
Query
Response
Field
Data
Field
Data
Slave Address
0x01
Slave Address
0x01
Function Code
0x06
Function Code
0x86
Start Address(Upper)
0x07
Exception Code
0x03
Start Address(Lower)
0xD1
Error Check(Lower)
0x02
Number of Registers(Upper)
0x01
Error Check(Upper)
0x61
Number of Registers(Lower)
0x0F
Error Check(Lower)
0x99
Error Check(Upper)
0x13
