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Adder⚓

Adder

Without Carry-out:

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signal A : signed (3 downto 0);
signal B : signed (3 downto 0);
signal S : signed (3 downto 0);
--
S <= A + B ; -- no overflow management

With Carry-out:

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signal A : signed (3 downto 0);
signal B : signed (3 downto 0);
signal S : signed (4 downto 0);
--
S <= resize(A, S'length) + resize(B, S'length); -- overflow managed

The size of the result of an addition of two operand is the size of the largest operand plus one.