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vhdl: add rrarbiter module

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Benjamin Krill 2013-09-17 12:52:29 +02:00
commit 439e9f2e57
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-- ---------------------------------------------------------------------------
-- (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;

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-- ---------------------------------------------------------------------------
-- (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.STD_Logic_unsigned.all;
use IEEE.numeric_std.all;
entity rrarbiter_tb is
end rrarbiter_tb;
architecture rtl of rrarbiter_tb is
constant CLK_PERIOD : time := 36 ns;
signal clk : std_logic;
signal rst : std_logic;
signal rst_n : std_logic;
signal req : std_logic_vector(6 downto 0);
signal grant : std_logic_vector(6 downto 0);
signal ack : std_logic;
begin
rst <= transport '1', '0' after ( 4 * CLK_PERIOD);
rst_n <= not rst;
clock: process
begin
clk <= '1', '0' after CLK_PERIOD/2;
wait for Clk_PERIOD;
end process;
beh: process
begin
req <= "0000000";
wait for 10*CLK_PERIOD;
req <= "0000011";
wait for 5*CLK_PERIOD;
req <= "0000000";
wait for 5*CLK_PERIOD;
req <= "0001111";
wait for 5*CLK_PERIOD;
req <= "0001110";
wait for 20*CLK_PERIOD;
req <= "0000000";
wait for 20*CLK_PERIOD;
wait;
end process beh;
beh0: process
begin
ack <= '0';
wait for 10*CLK_PERIOD;
wait for 6*CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for 8*CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for 5*CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for 2*CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
ack <= '1';
wait for CLK_PERIOD;
ack <= '0';
wait for CLK_PERIOD;
wait for 20*CLK_PERIOD;
wait;
end process beh0;
DUT: entity work.rrarbiter_reg
port map (
clk => clk,
rst_n => rst_n,
ack => ack,
req => req,
grant => grant
);
end rtl;
configuration rrarbiter_tb_rtl_cfg of rrarbiter_tb is
for rtl
end for;
end rrarbiter_tb_rtl_cfg;