source: PROJECT_CORE_MPI/CORE_MPI/BRANCHES/v1.00/Hold_FSM.vhd

----------------------------------------------------------------------------------
-- Company: 
-- Engineer: GAMOM Roland Christian
-- 
-- Create Date:    17:38:35 04/20/2013 
-- Design Name: 
-- Module Name:    Hold_FSM - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
----------------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx primitives in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity Hold_FSM is
    Port ( Hold_Req : in  STD_LOGIC;
           ram_busy : in  STD_LOGIC;
           Clk : in  STD_LOGIC;
           Reset : in  STD_LOGIC;
           Ramsel : out  STD_LOGIC;
           Hold_Ack : out  STD_LOGIC);
end Hold_FSM;

architecture Behavioral of Hold_FSM is
type typ_Hld is (Ht_Lock,Core_Lock,Ht_free);
signal Holdstate,Hold_st :typ_hld;
                signal Ram_sel :std_logic:='0';
                signal front_Rbusy,front_hReq:std_logic:='0';
begin

hold_sync:process (clk,reset)
 begin
 if rising_edge(clk) then
        
                
 end if;
 end process hold_sync;
 Ramsel_state:process(clk)--,HoldState,Hold_Req,ram_Busy,Front_HReq,Front_RBusy)
 
 begin
 
 if rising_edge(clk) then
 if reset='1' then
                HolDState<=Ht_free;
        else
--              HolDState<=Hold_St;
--       Hold_St<=HoldState;
 case HoldState is
 when Ht_free =>
        if Hold_Req='1' and ram_busy='0'   then
                HolDState <=Core_lock;
        elsif Hold_Req='0' and ram_busy='1' then
                HoldState <=HT_lock;
        elsif Hold_Req='1' and ram_busy='1' then
                HoldState <=HT_lock;
        else
                HoldState <=HT_free;
        end if;
 when Ht_lock =>
        if Hold_Req='0' and ram_busy='0'  then
                HoldState <=HT_free;
        elsif Hold_Req='1' and Ram_busy='0' then
                HoldState <=Core_lock;
        else
                HoldState <=HT_lock;
        end if;
 
 When Core_lock =>
        If Hold_Req='0' and Ram_busy='0' then
                HoldState <=HT_free;
        elsif Hold_Req='0' and Ram_busy='1' then
                HoldState <=HT_lock;
        else
                HoldState <=Core_lock;
        end if;
 end case ;
 end if;
 end if;

 end process;
 
  Ramsel_val:process(HoldState,Hold_Req,Ram_Busy)
 
 begin
 case HoldState is
 when Ht_free =>
 ram_sel<='0';
 Hold_Ack<='0';
 when Ht_Lock =>
 ram_sel<='0';
 Hold_Ack<='0';
 when Core_lock =>
 Ram_sel <='1';
 Hold_Ack<='1';
 end case;
 if Hold_Req= not(front_HReq) then
        front_HReq<= not front_HReq;
end if;

if Ram_busy= not (front_RBusy) then
        front_RBusy<= not front_RBusy;
end if;
 end process ramsel_val;
 Ramsel<=Ram_sel;
--=======================================================================
end Behavioral;