VHDL Conversion Functions

We could not be allowed to assign and integer to a binary value.  But we can use a conversion function such as To_unsigned to allow us to achieve this.


use IEEE.NUMERIC_STD.all;

...

signal A: Unsigned(7 downto 0);
signal F: Unsigned(2 downto 0);

...

Priority_encoder: process (A)
begin
  F <= "000";
  for I in 0 to 7 loop
    if A(I) = '1' then
      F <= To_unsigned(I, 3);
      exit;
    end if;
  end loop;
end process;


---
The example below is used to assign an integer to a type STD_LOGIC.


use IEEE.NUMERIC_STD.all;

...

signal A: Unsigned(7 downto 0);
signal S: Unsigned(2 downto 0);
signal G: Std_logic;

...

Mux: G <= A(To_integer(S));

Reference

http://www.doulos.com

This blog post contains notes taken when working through the Doulos Pacemaker tutorial.   Any content copied from the tutorial has been reproduced with permission.  http://www.doulos.com.