Modbus error 161 gets returned when trying to connect to a Modicon PLC with 'ProWORX 32'
'ProWORX 32', 'ProWORX NxT', 'Modsoft' and 'Concept'.
'Modbus error 161' is defined as an invalid address or address range.
To resolve the problem:
1.) Check the address and communications parameter setup to ensure that they are correct.
2.) Check the Modbus cable to see if the DSR connection is asserted high.
3.) Try placing the PLC into Dim Awareness and use the 'PLC & I/IO Status' function in Modsoft to
view the status. (If this is succcessful, download to the PLC using the default parameters of
(Modbus address, RTU, 8, Even, 1, 9600).