Reverse bit order on VHDL

Question

I\'m having trouble doing something like

b(0 to 7) <= a(7 downto 0)

when I compile it with ghdl, I have an order error. The only way I have

Answer 1

Suggestions?

Because your example specifies fixed length:

architecture rtl of reverser is 
    -- signal b: std_logic_vector (7 downto 0);

begin

    -- b(7) <= a(0);
    -- b(6) <= a(1);
    -- b(5) <= a(2);
    -- b(4) <= a(3);
    -- b(3) <= a(4);
    -- b(2) <= a(5);
    -- b(1) <= a(6);
    -- b(0) <= a(7);

    -- y <= b when rev = '1' else a;

    y <= a(0)&a(1)&a(2)&a(3)&a(4)&a(5)&a(6)&a(7) when rev = '1' else a;

end rtl;

The theory being that this should be less overhead than a function call or loop statement.