Convert Integer to Std_Logic
Suppose You Have a Loop for I in 1 Downto 0 Loop for J in 1 Downto 0 Loop tS0
Suppose you have a loop
for i in 1 downto 0 loop
for j in 1 downto 0 loop
tS0 <= i;
But I need to convert the integer (which is natural) to std_logic. tS0 is declared as std_logic. I am only doing it one bit (0 or 1). That is, my i and j can only represent the value {0,1}.
I think I am heading to the wrong approach here. Can someone please tell me what should I do instead?
I don't think std_logic has to_unsigned method. i tried letting tS0 to be a vector (1 down to 0), and assigned like tS0(0) <= i, and etc. But it still didn't work out.
Thank you very much!
5 Answers
There is no need to convert from integers. You can just iterate over the std_logic datatype:
for i in std_logic range '0' to '1' loop
ts0 <= i;
end loop;
I'd write a function:
function to_std_logic(i : in integer) return std_logic is
begin
if i = 0 then
return '0';
end if;
return '1';
end function;
then use:
ts0 <= to_std_logic(i);
You will need to use a vector, either unsigned or std_logic, but it can be one bit long. ie:
signal tS0 : unsigned (0 downto 0);
...
tS0 <= to_unsigned(i, tS0'length);
...or...
signal tS0: std_logic_vector(0 downto 0);
...
tS0 <= std_logic_vector(to_unsigned(i,tS0'length);
You can do it like this. It looks a little simplier.
ts0 <= std_logic(to_unsigned(i, 1)(0));
You will build a unsigned vector by using the to_unsigned function. Then you grap the lowest bit and convert it to std_logic and then you assign it to the signal.
This is how it works fine :-).
Improving on a previous answer, you could write:
ts0 <= to_unsigned(i, 1)(0);
Provided you include the "numeric_std" library, in which that function is defined:
library IEEE;
use IEEE.numeric_std.all;
You can skip the explicit cast to "std_logic" type because the return type of "to_unsigned()" is an array of "std_logic" itself:
type UNSIGNED is array (NATURAL range <>) of STD_LOGIC;
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