51
User Manual
MN032EN
Effective October 2017
215U-2 802.11
wireless I/O and gateway
EATON
www.eaton.com
Modbus error codes
The following are Modbus error response codes that the Modbus
RTU Master or TCP Client will generate and write to a general
purpose analog register (30501, 40501, and so on) in the event of
a poll fail. Codes 65281 through 65291 (FF01 through FF0B) reflect
Modbus error codes returned from the remote device as codes
01 through 0B. These codes and descriptions are taken from the
Modbus protocol reference. Codes 65024, 64512, 63488 and 65535
(FE00, FC00, F800, and FFFF) are generated by the Modbus master
(Client) on detection of an error with the communications such as a
failure to respond or a garbled message.
Code
(decimal)
Hex code
Name
Meaning
65281
FF01
Illegal Function
The function code received in the query is not an allowable action for the server (or slave).
This may be because the function code is only applicable to newer devices, and was not
implemented in the unit selected. It might also indicate that the server (or slave) is in the
wrong state to process a request of this type
65282
FF02
Illegal Data Address
The data address received in the query is 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, the PDU addresses the first register as 0, and the last one as 99.
If a request is submitted with a starting register address of 96 and a quantity of 4 registers,
this request will successfully operate on registers 96, 97, 98, 99. If a request is submitted with
a starting register address of 96 and a quantity of 5, this request will fail with Exception Code
0x02 “Illegal Data Address.”
65283
FF03
Illegal Data Value
A value contained in the query data field is not an allowable value for server (or slave). This
indicates a fault in the structure of the remainder of a complex request. For example, it may
indicate that the implied length is incorrect. It does not mean that a data item submitted
for storage in a register has a value outside the expectation of the application program.
The Modbus protocol is unaware of the significance of any particular value of any particular
register.
65384
FF04
Slave Device Failure
An unrecoverable error occurred while the server (or slave) was attempting to perform the
requested action
65285
FF05
Acknowledge
Specialized use in conjunction with programming commands (Included for completeness).
The server (or slave) has accepted the request and is processing it, but significant time will
be required to complete this task. This response is returned to prevent a timeout error from
occurring in the client (or master).
65286
FF06
Slave Device Busy
Specialized use in conjunction with programming commands (Included for completeness). The
server (or slave) is engaged in processing a long–duration program command. The client (or
master) should retransmit the message later when the server (or slave) is free.
65288
FF08
Memory Parity Error
Specialized use in conjunction with function codes 20 and 21 and reference type 6, to indicate
that the extended file area failed to pass a consistency check. (Included for completeness)
65290
FF0A
Gateway Path Unavailable
Specialized use in conjunction with gateways. Indicates that the gateway was unable to
allocate an internal communication path from the input port to the output port for processing
the request. Typically indicates that the gateway is mis-configured or overloaded.
65291
FF0B
Gateway Device Failed to Respond
Specialized use in conjunction with gateways. Indicates that no response was obtained from
the target device. Typically indicates that the device is not present on the network.
65024
FE00
Invalid Response from Slave
Command type or slave address did not match request. This error usually indicates that the
response from another request has been received after issuing the current request.
64512
FC00
Server Offline
Could not connect to the Modbus TCP server (Applies to Modbus TCP Client only).
63488
F800
Invalid Local Memory Address
Local address is invalid in the command. The memory location does not exist or is not
initialized
65535
FFFF
No Response
There was no response to the poll message
Error Response from Remote modbus Server (Slave)
Error code generated by local Modbus Client (Master)
