RAM initialization

[Mario]

Hello,

I am new in VHDL and I would like to make a question.

I saw in a site a RAM code and manipulated it to make a 15 bit address an 8
bit word RAM (32k)

Is there a possible way to initialize this RAM using an external file and
how?How this file should look like?

Here is the code :

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity RAM_32K is
port (
CLK : in std_logic;
WE : in std_logic; -- write enable
EN : in std_logic;
addr : in std_logic_vector(14 downto 0);
datain : in std_logic_vector(7 downto 0);
dataout : out std_logic_vector(7 downto 0));
end RAM_32K;

architecture RAM32 of RAM_32K is
type ram_type is array(32767 downto 0) of std_logic_vector(7 downto 0);
signal ram : ram_type;
begin
process(CLK)
begin
if (CLK'event and CLK = '1') then
if (en = '1') then
if (we = '1') then
ram(conv_integer(addr)) <= datain;
dataout <= datain;
else dataout <= ram(conv_integer(addr));
end if;
end if;
end if;
end process;
end;

 

[Mike Treseler]

Is there a possible way to initialize this RAM using an external file

This has been covered in comp.arch.fpga:
http://groups.google.com/groups?q=fpga+initialize+ram

I have modified your code (below) as an example of
how to use the numeric_std library.

Since you asked the vhdl newsgroup,
here's my vhdl skewed take on blockram initialization:

Why might I want to init a blockram during download?
There are two possible reasons.

1. I really need a rom, and should consider using a vhdl
constant array of vectors to infer the ROM from
block RAM without worrying about vendor specific files.

2. I have a local or external controller that
will do read and write cycles to this block ram.
In this case, consider inferring the RAM from
a template and init it (if need be) using the controller.

-- Mike Treseler
--------------------------------------------------------------

Here is the code :

-- modified to use numeric_std
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity RAM_32K is
port (
CLK : in std_logic;
WE : in std_logic; -- write enable
EN : in std_logic;
addr : in std_logic_vector(14 downto 0);
datain : in std_logic_vector(7 downto 0);
dataout : out std_logic_vector(7 downto 0));
end RAM_32K;

architecture RAM32 of RAM_32K is
type ram_type is array(32767 downto 0)
of std_logic_vector(7 downto 0);
signal ram : ram_type;
begin
process(CLK)
begin
if (CLK'event and CLK = '1') then
if (en = '1') then
if (we = '1') then
ram(to_integer(unsigned(addr))) <= datain;
dataout <= datain;
else
dataout <= ram(to_integer(unsigned(addr)));
end if;
end if;
end if;
end process;
end;