VHDL initialize generic array of std_logic_vector

Question

I would like to implement a ring buffer for convolution stuff in VHDL and make it generic. My problem is how to initialize the internal data without introducing further signals or variables.

Usually I can intialize the std_logic_vector by

signal initialized_vector : std_logic_vector(15 downto 0) := (others => '0');

But I have no clue how to do that onto an array by default.

Here's my code:

entity convolution_ringbuffer is
    generic (
        BitDepth_signal : integer := 24;
        BufferSize : integer := 10
        );
    port (
        data_in : in std_logic_vector(BitDepth_signal-1 downto 0);
        sclk : in std_logic;
        enable : in std_logic;
        data_out : out std_logic_vector(BitDepth_signal-1 downto 0)
        );
end convolution_ringbuffer;

architecture behavioral of convolution_ringbuffer is

    type internal_data is array(0 to BufferSize-1) of std_logic_vector(BitDepth_signal-1 downto 0);
    signal data_internal : internal_data;

begin

    process ( sclk ) 

        variable current_position : integer range 0 to (BufferSize-1) := 0;

    begin

        if ( rising_edge(sclk) and enable = '1' ) then

            data_internal(current_position) <= std_logic_vector(data_in);

            if ( current_position < BufferSize-1 ) then
                current_position := current_position + 1;    
            else
                current_position := 0;
            end if;

        end if;

        if ( falling_edge(sclk) ) then
            data_out <= std_logic_vector(data_internal(current_position));
        end if;

    end process;

end behavioral;

Juergen · Accepted Answer · 2017-11-22 13:49:43Z

6

You can do almost the same as for std_logic_vector. You just have to consider that you have one more dimension:

signal data_internal : internal_data := (others=>(others=>'0'));

If you have more complex initialization data to store, you could use an initialization function:

function init return internal_data is
begin
    --do something (e.g. read data from a file, perform some initialization calculation, ...)
end function init;

signal data_internal : internal_data := init;

answered Nov 22, 2017 at 13:49

Juergen

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