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Altera_Forum
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10 years ago

VHDL : Problem with 4-Bit Adder and Subtractor !

Hi I want to make a 4-Bit Adder and Subtractor with VHDL I have created 1-Bit Full-Adder , XOR Gate ( for Subtract ) and a 4-Bit Adder as shown below : Full-Adder : LIBRARY ieee; USE i...
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Altera_Forum
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10 years ago

You cant make the rule in the code when you treat the code as if it were a programming language. But this is not a programming language, it is a hardware description language - therefore you need to know what the hardware will be before you write the code!

You need to take a step back, and draw the circuit you expect. If you dont know what to expect, then you need to go and get a text book on digital logic design. Trying to treat VHDL as if it were a programming language just leads to bad results, or just no results at all.