>I don't understand the need to have the system interface
>floating when programming a non-isolated AC-powered target
>device. I assume by "non-isolated," they mean the target
>device's ground is an earth ground

By 'non-isolated' I think they mean there is no transformer in the mains 
supply to the target device, when running off mains power. Personally I 
would be very worried about doing this as it means all the test equipment is 
connected to mains potential, and hence potentially (no pun intended) 
lethal.

On the other hand they may be talking about the earth, as it could be 
possible to have an earth loop through the ICD and test equipment back to 
the mains earth, as well as the earth direct from the target to mains earth. 
This could induce significant fault currents around the loop, and may be the 
cause of ICD buffers being destroyed (as has been reported here at various 
times). 

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