Variable length STD in VHDL_ logic_ Vector initialization

I have a variable length vector STD_ logic_ vector(X downto 0). Now I try to define a constant in my package for reset, so that the lower X / 2 bit is 1 and the others are 0

For example, a 3-bit vector (x = 3) will give the constant "011", while a 4-bit vector will give the constant "0011"

How can I do this in a VHDL package? The following code explains what I want to do

type Entry_Type is record
  state : std_logic_vector(X-1 downto 0);
end record;
constant Entry_Constant : Entry_Type := <???>;

Solution

There are at least two options to initialize your record type as needed One is to use initialization function, the other is to use the value of N in aggregation

Function is a good way to initialize custom data types In your case, you can create the function default_ entry_ from_ Width (n), return entry_ Type value:

type entry_type is record
    state: std_logic_vector;
end record;

function default_entry_from_width(width: natural) return entry_type is
    variable return_vector: std_logic_vector(width-1 downto 0);
begin
    for i in return_vector'range loop
        return_vector(i) := '1' when i <= width/2 else '0';
    end loop;
    return (state => return_vector);
end;

constant ENTRY_1: entry_type := default_entry_from_width(3);  -- return 011
constant ENTRY_2: entry_type := default_entry_from_width(4);  -- return 0011

Another method is to initialize constants with aggregates using predefined n values:

constant N: natural := 4;
constant ENTRY_3: entry_type := (
    state => (
        N-1 downto N/2 => '1',N/2-1 downto 0 => '0'
    )
);