Rev Version 1.4.1
103
103
Rev Version 1.4.1
Appendix
E - MODBUS EXCEPTION CODES
The following are Modbus exception codes that the Master will generate and write to a general purpose analog
register (30501, 40501, and so on) in the event of a poll fail.
Dec Code
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 could
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 with a quantity of 4
registers, then 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 registers 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, 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.
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.
The server (or slave) has accepted the request and is processing it, but a
significant amount of 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.
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.
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. Usually means that the
gateway is misconfigured 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. Usually means that the device is not
present on the network
65024
FE00
Invalid Response
from Slave
Command type or slave address did not match request (the address may
belong to another unit).
64512
FC00
Server Offline
Could not connect to Modbus TCP server.
63488
F800
Invalid Local Memory
Address
Local address invalid in command. Memory location does not exist or is
not initialized.
65535
FFFF
No Response to the
Poll
No response to poll message.
