ProSoft MVI56E-MCMR User Manual page 189

MVI56E-MCMR ♦ ControlLogix Platform
Modbus Communication Module with Reduced Data Block
Modbus Exception Codes
Code Name
01 Illegal Function
02 Illegal Data Address
03 Illegal Data Value
04 Slave Device Failure
05 Acknowledge
06 Slave Device Busy
08 Memory Parity Error
0a Gateway Path Unavailable Specialized use in conjunction with gateways, indicates that the
0b Gateway Target Device
Failed To Respond
ProSoft Technology, Inc.
Meaning
The function code received in the query is not an allowable
action for the 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 Slave is in the
wrong state to process a request of this type, for example
because it is unconfigured and is being asked to return register
values.
The data address received in the query is not an allowable
address for the 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 will generate
exception 02.
A value contained in the query data field is not an allowable
value for 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, because the Modbus
protocol is unaware of the significance of any particular value of
any particular register.
An unrecoverable error occurred while the Slave was attempting
to perform the requested action.
Specialized use in conjunction with programming commands.
The Slave has accepted the request and is processing it, but a
long duration of time will be required to do so. This response is
returned to prevent a timeout error from occurring in the Master.
The Master can next issue a poll program complete message to
determine if processing is completed.
Specialized use in conjunction with programming commands.
The Slave is engaged in processing a long-duration program
command. The Master should retransmit the message later when
the Slave is free.
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. The Slave attempted to read record
file, but detected a parity error in the memory. The Master can
retry the request, but service may be required on the Slave
device.
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.
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.
Reference
User Manual
Page 189 of 223