How to set to 0 value unconnected input pin?

Thank you for your quick replies!

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Wouldn't it simply to just set your pins as GND source instead of VCC on your input pins?

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I think that is what i'm trying to do. But i don't know how to do it internally in Quartus II or by scripting. I'm totally beginner.

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The unused pins are set in project assignments => device => device and pin options => unused pins

There are several options:

1) default(hopefully) "as tristated inputs with weak pullup", Quartus connects it to Vcc internally, no need for pcb wiring to Vcc

2) "as tristated inputs", you need to connect to board Vcc or ground

3) "as output driving ground", quartus connects it to gnd internally, no need for wiring to pcb gnd. This is what you are after, provides more ground.

4) "as outputs driving unspecified signal",

5) "as tristated inputs with bus hold circuitry"

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I have tried to set "as output driving ground" to all unused pins, but when I do it, the programmer tool fails to program my device.

I can't quite understand whether unused pins, are all those pins that are assigned in pin planner but not wired on board, or those are pins that are not assigned in pin planner at all?

I mean, I want to use pin as ordinary input but when I unplug connector to it, the pin value should be 0. And unfortunately there is no pull-down resistor.