56 lines
2.0 KiB
VHDL
56 lines
2.0 KiB
VHDL
-- ---------------------------------------------------------------------------
|
|
-- (2009) Benjamin Krill <ben@codiert.org>
|
|
--
|
|
-- "THE BEER-WARE LICENSE" (Revision 42):
|
|
-- ben@codiert.org wrote this file. As long as you retain this notice you can
|
|
-- do whatever you want with this stuff. If we meet some day, and you think
|
|
-- this stuff is worth it, you can buy me a beer in return Benjamin Krill
|
|
-- ---------------------------------------------------------------------------
|
|
library ieee;
|
|
use ieee.std_logic_1164.all;
|
|
use ieee.numeric_std.all;
|
|
|
|
entity rrarbiter is
|
|
generic ( CNT : integer := 7 );
|
|
port (
|
|
clk : in std_logic;
|
|
rst_n : in std_logic;
|
|
|
|
req : in std_logic_vector(CNT-1 downto 0);
|
|
ack : in std_logic;
|
|
grant : out std_logic_vector(CNT-1 downto 0)
|
|
);
|
|
end;
|
|
|
|
architecture rrarbiter of rrarbiter is
|
|
signal grant_q : std_logic_vector(CNT-1 downto 0);
|
|
signal pre_req : std_logic_vector(CNT-1 downto 0);
|
|
signal sel_gnt : std_logic_vector(CNT-1 downto 0);
|
|
signal isol_lsb : std_logic_vector(CNT-1 downto 0);
|
|
signal mask_pre : std_logic_vector(CNT-1 downto 0);
|
|
signal win : std_logic_vector(CNT-1 downto 0);
|
|
begin
|
|
grant <= grant_q;
|
|
mask_pre <= req and not (std_logic_vector(unsigned(pre_req) - 1) or pre_req); -- Mask off previous winners
|
|
sel_gnt <= mask_pre and std_logic_vector(unsigned(not(mask_pre)) + 1); -- Select new winner
|
|
isol_lsb <= req and std_logic_vector(unsigned(not(req)) + 1); -- Isolate least significant set bit.
|
|
win <= sel_gnt when mask_pre /= (CNT-1 downto 0 => '0') else isol_lsb;
|
|
|
|
process (clk,rst_n)
|
|
begin
|
|
if rst_n = '0' then
|
|
pre_req <= (others => '0');
|
|
grant_q <= (others => '0');
|
|
elsif rising_edge(clk) then
|
|
grant_q <= grant_q;
|
|
pre_req <= pre_req;
|
|
if grant_q = (CNT-1 downto 0 => '0') or ack = '1' then
|
|
if win /= (CNT-1 downto 0 => '0') then
|
|
pre_req <= win;
|
|
end if;
|
|
grant_q <= win;
|
|
end if;
|
|
end if;
|
|
end process;
|
|
end rrarbiter;
|