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Exception codes
MODBUS protocol manual
6. EXCEPTION CODES
When the instrument receives a not-valid query, an error message (exception code) is sent.
According to the used MODBUS protocol mode, possible exception codes are as follows.
MODBUS ASCII/RTU
Values contained in Response messages are in hexa format.
Response example in case of MODBUS ASCII/RTU: 0183000131F0
Example Byte Description No. of bytes
01 - Slave address 1
83 - Function code (80+03) 1
00 High
Exception code 2
01 Low
31 High
Error check (CRC) 2
F0 Low
Exception codes for MODBUS ASCII/RTU are following described:
0001 ILLEGAL FUNCTION: the function code received in the query is not an allowable
action.
0002 ILLEGAL DATA ADDRESS: the data address received in the query is not an allowable
address (i.e. the combination of register and transfer length is invalid).
0003 ILLEGAL DATA VALUE: a value contained in the query data field is not an allowable
value.
0004 ILLEGAL RESPONSE LENGTH: the request would generate a response with size bigger
than that available for MODBUS protocol.
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