DE1 Control Panel

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so means DE1 seven segment cathode type?

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Incorrect. The displays are common anode, which is connected to +3.3V. There is an inline 1K current limit resistor from the individual segment cathode to the FPGA pin.

So you need to drive a pin LOW to light the corresponding segment. So '1' = off, '0' = on are the levels required on the FPGA segment driver pins.