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Visitor
Visitor
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Registered: ‎10-12-2018

Logical operation problem

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Hi All!


I'm new in vhdl programming. I just started tutorial trainings and got some problem.


I'm using ISE 14.7 version. Development board Waveshare DVK601, Core3S250E.
It was programmed simple AND logical operation between two inputs.

For example y<=i0 and i1; Simulation has done and worked how should be.


After flashing the Core, it works like OR logical operation. Then I tested back and found that OR operation works like AND operation.

 

Did anybody had such a problem? Maybe I missed something?

 

Thanks in advance

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Advisor
Advisor
686 Views
Registered: ‎04-26-2015

I would guess that your inputs and outputs are inverted.

 

For inputs this is achieved by having switches that float high, but pressing the switch pulls them down to ground. Pressing the switch gets a zero, releasing it gets a one.

 

For outputs, it's because the LED anode is connected to 3.3V through a resistor and the LED cathode is connected to the FPGA pin. Setting the pin to 1 (3.3V) means there's no voltage across the LED and therefore no light; setting the pin to 0 (0V) means that the LED turns on.

 

Inverting all inputs and the output of an OR gate turns it into an AND gate, and vice versa.

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Advisor
Advisor
687 Views
Registered: ‎04-26-2015

I would guess that your inputs and outputs are inverted.

 

For inputs this is achieved by having switches that float high, but pressing the switch pulls them down to ground. Pressing the switch gets a zero, releasing it gets a one.

 

For outputs, it's because the LED anode is connected to 3.3V through a resistor and the LED cathode is connected to the FPGA pin. Setting the pin to 1 (3.3V) means there's no voltage across the LED and therefore no light; setting the pin to 0 (0V) means that the LED turns on.

 

Inverting all inputs and the output of an OR gate turns it into an AND gate, and vice versa.

View solution in original post

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Visitor
Visitor
657 Views
Registered: ‎10-12-2018
Ah!
Problem solved. I stucked at one point only, but should check the my board schematics.
Thank you, u4223374.
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