altera FPGA acting like OR gate when programed as AND gate

Question

I'm new to altera fpga , I've bought development board based on EP4CE6E22 cyclon IV and tryed to program it with basic program in quartus environment

module my_and(a,b,c);  
input a,b;  
output c;  
assign c = a & b; 
endmodule

I've loaded pin assignment from files that came with the board and programmed it with some chinese jtag blaster.

but when i tryed to push one or the other or both (attached to a,b signals)button - the led turned on , and went off when released (like OR GATE)

so i tryed to program it as OR GATE gate and the board started acting like AND GATE

am i doing somthing wrong?

Answer 1

Your switches will be active low (i.e. zero when pressed). Your LEDs will also be active low (i.e. zero will turn them on).

If you invert the inputs and output of an AND gate, you get an OR gate, hence the behaviour you are seeing.

There is nothing wrong with the FPGA.