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May I suggest "As inputs with weak pull-up" as the default? It's less likely to damage something than driving ground as well as able to deal with floating inputs.
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I recommend setting "Device and Pin Options --> Unused Pins --> Reserve all unused pins" to "As input tri-stated with bus-hold circuitry" for device families that offer that choice. As I said in a post for another topic, bus hold has no conflict with an unused pin being grounded on the board. With the weak pull-up, you'll have a little wasted power.
I had noticed that this default changed in Quartus for some device families, so I checked to see what QII 7.1 gives for a few cases. When I created a new project for each of the following families, I got the following. It looks like your request has already been granted for most new families.
- "As input tri-stated with weak pull-up resistor" for Cyclone III (new family)
- "As input tri-stated with weak pull-up resistor" for Stratix III (new family)
- "As output driving ground" for Arria GX (new family, so not every new family has the change)
- "As output driving ground" for Stratix II and Stratix II GX (this is probably still the default for all older families too)
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