Orientalmotor BLV Series, User Manual, Page: 15 / 40

Method of control via Modbus protocol
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• Exception response
An exception response is returned if the slave cannot execute the process requested by the query. Appended
to this response is an exception code indicating why the process cannot be executed. The message structure of
exception response is as follows.
Slave address Function code Exception code Error check
8 bits 8 bits 8 bits 16 bits
Function code
The function code in the exception response is a sum of the function code in the query and 80h.
Example) query: 03h
→
Exception response: 83h
Exception code
This code indicates why the process cannot be executed.
Exception
code
Communication
error code
Cause Description
01h
88h
Invalid
function
The process could not be executed because the function code was
invalid.
· The function code is not supported.
· The sub-function code for diagnosis (08h) is other than 00h.
02h
Invalid data
address
The process could not be executed because the data address was invalid.
· The register address is not supported (other than 0000h to 1FFFh).
· The register address and the number of registers are 2000h or more in
total.
03h 8Ch Invalid data
The process could not be executed because the data was invalid.
· The number of registers is 0 or more than 17.
· The number of bytes is other than twice the number of registers.
· The data length is outside the specified range.
04h
89h
8Ah
8Ch
8Dh
Slave error
The process could not be executed because an error occurred at the
slave.
•
User interface communication in progress (89h)
Download, initialization or teaching operation is in progress using the
MEXE02 or OPX-2A .
• NV memory processing in progress (8Ah)
· Internal processing is in progress (S-BSY is ON).
· An EEPROM error alarm is present.
•
Outside the parameter setting range (8Ch)
The value write is outside the setting range.
•
Command execute disable (8Dh)
Example of exception response
Slave address 01h
Function code 06h
Register address (upper)
Data
02h
Error check (lower) E9h
Error check (upper) C4h
Slave address 01h
Function code 86h
Data Exception code 04h
Register address (lower) 1Eh
Value write (upper)
FFh
Value write (lower) FFh
Error check (lower) 02h
Error check (upper) 61h
Master
Query
Response
Slave