7
7 System Design Responsibility
8 Laws and Regulations
● Please make sure to comply with laws and regulations in terms of Modbus communication designed locally.
6.4 Exception code
When the message from the master device is not valid, the interface unit will discard the message and respond exception code.
The structure of exception response is shown below.
1
Slave address
2
Function code + 80h
3
Exception code
4
CRC-16
The description of exception codes in exception response is shown in the table below.
Code Name
Description
01h
ILLEGAL FUNCTION
The function code received in the query is not an allowable action for the slave (the interface unit).
02h
ILLEGAL DATA ADDRESS
The data address received in the query is not allowable address for the slave (the interface unit).
03h
ILLEGAL DATA VALUE
A value contained in the query data field is not an allowable value for the slave (the interface unit).
6
Function code and Data address
● Mitsubishi Electric does not take any responsibility on the local system design of Modbus communication.
