For testing how to use input in EPM240T100C5 physically, I set up the following buffer .bfd :
Supposedly, when I connect the available VCC to PIN 55, the PIN 57 will be HIGH. Else, PIN 57 should be low.
However, once I programmed the board, the PIN 57 is HIGH all the time.
I then tested using other gates like AND gate instead of directly connecting input and output together. Still, the output is always HIGH.
How should I properly use input in physical circuit? Thanks!
What a careless mistake. I forgot to connect the ground. It should look something like this.
Basically, it is VCC => push button => ground, and in between push button and ground, just take a wire input to the input pin.