Chapter 4 Exception Codes - Mitsubishi Electric MELSEC iQ-R Series Reference Manual

4
EXCEPTION CODES
Exception codes are error codes that are common to the MODBUS protocol and are stored in the response message when a
slave returns an abnormal response for the request message from the master.
When the master receives an exception code from a slave, perform actions according to the description in this chapter.
The response message format when processing completed with an error is shown below.
b15
(1)
(1) Abnormal response function code
(2) Exception code
Abnormal response function code list
This section lists the abnormal response function codes that are stored in the upper byte of the response message format.
Abnormal response function code
81H
82H
83H
84H
85H
86H
87H
88H
8BH
8CH
8FH
90H
91H
94H
95H
96H
97H
4 EXCEPTION CODES
50
b8 b7
(2)
Function name
Read coils
Read discrete inputs
Read holding registers
Read input registers
Write single coil
Write single register
Read exception status
Page 13 Diagnosis function details
Get communications event counter
Get communications event log
Write multiple coils
Write multiple registers
Report slave ID
Read file record
Write file record
Mask write register
Read/Write multiple registers
b0
Details
'Read coils' completed with an error.
'Read discrete inputs' completed with an error.
'Read holding registers' completed with an error.
'Read input registers' completed with an error.
'Write single coil' completed with an error.
'Write single holding register' completed with an error.
'Read exception status' completed with an error.
'Diagnostics' completed with an error.
'Get communications event counter' completed with
an error.
'Get communications event log' completed with an
error.
'Write multiple coils' completed with an error.
'Write multiple holding registers' completed with an
error.
'Report slave ID' completed with an error.
'Read file record' completed with an error.
'Write file record' completed with an error.
'Mask write register' completed with an error.
'Read/Write multiple registers' completed with an
error.