If you are using Visual basic it is best to compute the FCS (frame check sequence) and attached before the "*". Otherwise the PLC will reject the command string without a FCS.
If the PLC is in Auto protocol mode (default) you can also substitute the FCS with just "00*" which the PLC will take a a "wildcard" and accept it.
When you execute WO correctly, and if the output is NOT controlled by the ladder program then it will latch. To verify this, first transfer a blank program to the PLC and you will then be able to send WO command. The easiest way to test the command is to use TLServer's "Command String" text box.
When you write to a physical input it will never latch because the PLC will overwrite any changes to its input register as soon as it performs the next I/O scan (which happen after every ladder logic program scan). However, it is possible to make it change for 1 scan time which may be enough to trigger an action in the PLC.
