In-Situ Aqua TROLL 400 Modbus and SDI-12 Reference Guide - Manual (Page 66)

8.12 Exception Codes
The instrument manufacturer supports the standard Modbus exception codes but also provides
additional exception codes to assist with troubleshooting problems.
Code Name Description
1 Illegal Function The function code received in the query is not an allowable action for
the slave. If a Poll Program Complete command was issued, this code
indicates that no program function preceded it.
2 Illegal Data Address The data address received in the query is not an allowable address for
the slave.
3 Illegal Data Value A value contained in the query data field is not an allowable value for
the slave.
4 Slave Device Failure An unrecoverable error occurred while the slave was attempting to
perform the requested action.
5 Acknowledge 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.
This exception code may not be supported by the devices
6 Slave Device Busy The slave is engaged in processing a long–duration program
command. The master should retransmit the message later when the
slave is free.
This exception code may not be supported by the devices
8 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.
The server (or slave) attempted to read record file, but
detected a parity error in the memory. The client (or master)
can retry the request, but service may be required on the
server (or slave) device.
This exception code may not be supported by the devices
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