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--
-- Asymmetric port RAM
-- Port A is 256x8-bit read-and-write (write-first synchronization)
-- Port B is 64x32-bit read-and-write (write-first synchronization)
-- Compact description with a for-loop statement
--
-- Download: ftp://ftp.xilinx.com/pub/documentation/misc/xstug_examples.zip
-- File: HDL_Coding_Techniques/rams/asymmetric_ram_2b.vhd
--
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity asymmetric_ram_2b is
generic (
WIDTHA : integer := 8;
SIZEA : integer := 256;
ADDRWIDTHA : integer := 8;
WIDTHB : integer := 32;
SIZEB : integer := 64;
ADDRWIDTHB : integer := 6
);
port (
clkA : in std_logic;
clkB : in std_logic;
enA : in std_logic;
enB : in std_logic;
weA : in std_logic;
weB : in std_logic;
addrA : in std_logic_vector(ADDRWIDTHA-1 downto 0);
addrB : in std_logic_vector(ADDRWIDTHB-1 downto 0);
diA : in std_logic_vector(WIDTHA-1 downto 0);
diB : in std_logic_vector(WIDTHB-1 downto 0);
doA : out std_logic_vector(WIDTHA-1 downto 0);
doB : out std_logic_vector(WIDTHB-1 downto 0)
);
end asymmetric_ram_2b;
architecture behavioral of asymmetric_ram_2b is
function max(L, R: INTEGER) return INTEGER is
begin
if L > R then
return L;
else
return R;
end if;
end;
function min(L, R: INTEGER) return INTEGER is
begin
if L < R then
return L;
else
return R;
end if;
end;
function log2 (val: INTEGER) return natural is
variable res : natural;
begin
for i in 0 to 31 loop
if (val <= (2**i)) then
res := i;
exit;
end if;
end loop;
return res;
end function Log2;
constant minWIDTH : integer := min(WIDTHA,WIDTHB);
constant maxWIDTH : integer := max(WIDTHA,WIDTHB);
constant maxSIZE : integer := max(SIZEA,SIZEB);
constant RATIO : integer := maxWIDTH / minWIDTH;
type ramType is array (0 to maxSIZE-1) of std_logic_vector(minWIDTH-1 downto 0);
shared variable ram : ramType := (others => (others => '0'));
signal readA : std_logic_vector(WIDTHA-1 downto 0):= (others => '0');
signal readB : std_logic_vector(WIDTHB-1 downto 0):= (others => '0');
signal regA : std_logic_vector(WIDTHA-1 downto 0):= (others => '0');
signal regB : std_logic_vector(WIDTHB-1 downto 0):= (others => '0');
begin
process (clkA)
begin
if rising_edge(clkA) then
if enA = '1' then
if weA = '1' then
ram(conv_integer(addrA)) := diA;
end if;
readA <= ram(conv_integer(addrA));
end if;
regA <= readA;
end if;
end process;
process (clkB)
begin
if rising_edge(clkB) then
if enB = '1' then
if weB = '1' then
for i in 0 to RATIO-1 loop
ram(conv_integer(addrB & conv_std_logic_vector(i,log2(RATIO))))
:= diB((i+1)*minWIDTH-1 downto i*minWIDTH);
end loop;
end if;
for i in 0 to RATIO-1 loop
readB((i+1)*minWIDTH-1 downto i*minWIDTH)
<= ram(conv_integer(addrB & conv_std_logic_vector(i,log2(RATIO))));
end loop;
end if;
regB <= readB;
end if;
end process;
doA <= regA;
doB <= regB;
end behavioral;
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