entity plru is
generic (
- BITS : positive := 2
- )
- ;
+ BITS : positive := 2
+ )
+ ;
port (
- clk : in std_ulogic;
- rst : in std_ulogic;
+ clk : in std_ulogic;
+ rst : in std_ulogic;
- acc : in std_ulogic_vector(BITS-1 downto 0);
- acc_en : in std_ulogic;
- lru : out std_ulogic_vector(BITS-1 downto 0)
- );
+ acc : in std_ulogic_vector(BITS-1 downto 0);
+ acc_en : in std_ulogic;
+ lru : out std_ulogic_vector(BITS-1 downto 0)
+ );
end entity plru;
architecture rtl of plru is
-- XXX Check if we can turn that into a little ROM instead that
-- takes the tree bit vector and returns the LRU. See if it's better
- -- in term of FPGA resouces usage...
+ -- in term of FPGA resource usage...
get_lru: process(tree)
- variable node : node_t;
+ variable node : node_t;
begin
- node := 0;
- for i in 0 to BITS-1 loop
--- report "GET: i:" & integer'image(i) & " node:" & integer'image(node) & " val:" & std_ulogic'image(tree(node));
- lru(BITS-1-i) <= tree(node);
- if i /= BITS-1 then
- node := node * 2;
- if tree(node) = '1' then
- node := node + 2;
- else
- node := node + 1;
- end if;
- end if;
- end loop;
+ node := 0;
+ for i in 0 to BITS-1 loop
+-- report "GET: i:" & integer'image(i) & " node:" & integer'image(node) & " val:" & std_ulogic'image(tree(node));
+ lru(BITS-1-i) <= tree(node);
+ if i /= BITS-1 then
+ node := node * 2;
+ if tree(node) = '1' then
+ node := node + 2;
+ else
+ node := node + 1;
+ end if;
+ end if;
+ end loop;
end process;
update_lru: process(clk)
- variable node : node_t;
- variable abit : std_ulogic;
+ variable node : node_t;
+ variable abit : std_ulogic;
begin
- if rising_edge(clk) then
- if rst = '1' then
- tree <= (others => '0');
- elsif acc_en = '1' then
- node := 0;
- for i in 0 to BITS-1 loop
- abit := acc(BITS-1-i);
- tree(node) <= not abit;
--- report "UPD: i:" & integer'image(i) & " node:" & integer'image(node) & " val" & std_ulogic'image(not abit);
- if i /= BITS-1 then
- node := node * 2;
- if abit = '1' then
- node := node + 2;
- else
- node := node + 1;
- end if;
- end if;
- end loop;
- end if;
- end if;
+ if rising_edge(clk) then
+ if rst = '1' then
+ tree <= (others => '0');
+ elsif acc_en = '1' then
+ node := 0;
+ for i in 0 to BITS-1 loop
+ abit := acc(BITS-1-i);
+ tree(node) <= not abit;
+-- report "UPD: i:" & integer'image(i) & " node:" & integer'image(node) & " val" & std_ulogic'image(not abit);
+ if i /= BITS-1 then
+ node := node * 2;
+ if abit = '1' then
+ node := node + 2;
+ else
+ node := node + 1;
+ end if;
+ end if;
+ end loop;
+ end if;
+ end if;
end process;
end;
-
-