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rvais1's avatar
rvais1
Icon for New Contributor rankNew Contributor
7 years ago
Solved

and gate acting as or and vysa versa

hey

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?

  • ak6dn's avatar
    ak6dn
    7 years ago

    Check the logic sense of your switches and LED pins. You are assuming PUSHed=1 and not=0, and out=1 for LED on, and out=0 for LED off.

    On many/most all boards pushbuttons will be connected to a pin with a pullup, so the default input will be a '1' (high). When you push it it goes to a '0' (low).

    The LED could be driven either active high ('1' high for ON, '0' low for OFF) or active low ('1' high for OFF, '0' low for ON). Check the schematic/docs for which way on your board.

1 Reply

  • ak6dn's avatar
    ak6dn
    Icon for Regular Contributor rankRegular Contributor
    7 years ago

    Check the logic sense of your switches and LED pins. You are assuming PUSHed=1 and not=0, and out=1 for LED on, and out=0 for LED off.

    On many/most all boards pushbuttons will be connected to a pin with a pullup, so the default input will be a '1' (high). When you push it it goes to a '0' (low).

    The LED could be driven either active high ('1' high for ON, '0' low for OFF) or active low ('1' high for OFF, '0' low for ON). Check the schematic/docs for which way on your board.