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what do you mean with schmitt inputs? schmitt-triggered inputs that might be used to debounce your input signal(s)?? If you need to debounce your signal, try to use shiftregisters that "detect" your edges and logical state of the signal (as far I remember there is some additional register available too in near of the pad, but I'm not sure)
Hope it helped,
I haven't used this feature yet, but I think it should be possible by editing the ucf (user constraint file) or passing some attribute in your HDL code ;
please check the docu or maybe somebody else can help you, sorry for any inconvenience.
I think the inputs are by definition kind of shmit triggers, as you can set input levels to TTL or CMOS. a '1' is detected for a certain analogue level, which isn't the same as a '0'.
But if you want to debounce a signal digitaly for a switch, a shmit trigger is not what you need, as the input signal will go from high to low several times. a simple way to do it is is use register with a slow clock
if clk'event and clk='1' then
output<=registered_1 and registered_2 and input