Rs485: Modbus Rtu Message Function Codes - Danfoss VLT AutomationDrive FC 361 Series Design Manual

Appendix
11.9 RS485: Modbus RTU Message Function
Codes
11.9.1 Function Codes Supported by
Modbus RTU
Modbus RTU supports use of the function codes in
Table 11.17 in the function field of a message.
Function
Read coils
Read holding registers
Write single coil
Write single register
Write multiple coils
Write multiple registers
Get comm. event counter
Report slave ID
Table 11.17 Function Codes
Function Function Sub-
code function
code
Diagnostics 8 1
2
10
11
12
13
14
Table 11.18 Function Codes
MG06K102
Design Guide
Function code
1 hex
3 hex
5 hex
6 hex
F hex
10 hex
B hex
11 hex
Sub-function
Restart communication.
Return diagnostic register.
Clear counters and
diagnostic register.
Return bus message count.
Return bus communication
error count.
Return bus exception error
count.
Return slave message
count.
Danfoss A/S © 03/2019 All rights reserved.
11.9.2 Modbus Exception Codes
For a full explanation of the structure of an exception code
response, refer to chapter 11.8 RS485: Modbus RTU Telegram
Structure.
Code Name Meaning
1 Illegal The function code received in the query is
function not an allowable action for the server (or
slave). This code can be because the
function code is only applicable to newer
devices and was not implemented in the
unit selected. It could also indicate that
the server (or slave) is in the wrong state
to process a request of this type, for
example because it is not configured and
is being asked to return register values.
2 Illegal data The data address received in the query is
address not an allowable address for the server
(or slave). More specifically, the
combination of reference number and
transfer length is invalid. For a controller
with 100 registers, a request with offset
96 and length 4 would succeed, a request
with offset 96 and length 5 generates
exception 02.
3 Illegal data A value contained in the query data field
value is not an allowable value for server (or
slave). This code indicates a fault in the
structure of the remainder of a complex
request, such as that the implied length is
incorrect. It specifically does NOT mean
that a data item submitted for storage in
a register has a value outside the
expectation of the application program,
since the Modbus protocol is unaware of
the significance of any particular value of
any particular register.
4 Slave device An unrecoverable error occurred while the
failure server (or slave) was attempting to
perform the requested action.
Table 11.19 Modbus Exception Codes
11 11
87