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library ieee;
use ieee.std_logic_1164.all;
library ieee;
use ieee.numeric_std.all;
entity extend_mask is
port (
clk : in std_logic;
ra0_addr : in std_logic_vector(4 downto 0);
ra0_data : out std_logic_vector(20 downto 0)
);
end extend_mask;
architecture augh of extend_mask is
-- Embedded RAM
type ram_type is array (0 to 19) of std_logic_vector(20 downto 0);
signal ram : ram_type := (
"111111111111111111110", "111111111111111111100", "111111111111111111000", "111111111111111110000",
"111111111111111100000", "111111111111111000000", "111111111111110000000", "111111111111100000000",
"111111111111000000000", "111111111110000000000", "111111111100000000000", "111111111000000000000",
"111111110000000000000", "111111100000000000000", "111111000000000000000", "111110000000000000000",
"111100000000000000000", "111000000000000000000", "110000000000000000000", "100000000000000000000"
);
-- Little utility functions to make VHDL syntactically correct
-- with the syntax to_integer(unsigned(vector)) when 'vector' is a std_logic.
-- This happens when accessing arrays with <= 2 cells, for example.
function to_integer(B: std_logic) return integer is
variable V: std_logic_vector(0 to 0);
begin
V(0) := B;
return to_integer(unsigned(V));
end;
function to_integer(V: std_logic_vector) return integer is
begin
return to_integer(unsigned(V));
end;
begin
-- The component is a ROM.
-- There is no Write side.
-- The Read side (the outputs)
ra0_data <= ram( to_integer(ra0_addr) ) when to_integer(ra0_addr) < 20 else (others => '-');
end architecture;
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