Error: Type conversion (to UNSIGNED) can not have string literal operand

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Change the line near the end to:

DATA<= unsigned(DATAi)-UNSIGNED(std_logic_vector'(X"80")) when SIGNED_DATA=0 else DATAi;

Note the change to enforce that the argument to UNSIGNED() is a std_logic_vector.

Cheers,

Dave

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Hai Dave,

Thanks, its can simulate know..I have another question, can you help me to verify it. I have line code of bp<=SXT(a,9) + b and bp<= a+b, wheres a and b is std_logic_vector(7 downto 0) and bp is std_logic_vector(8 downto 0). My question is what the different between the two line codes? thanks in advance