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-- File Name   : in_key.fsm                                     -- 
-- Description : The control of in key blok                     --
-- Purpose     : To be used by SYF                              --
-- Date        : Aug 30, 2001                                   --
-- Version     : 1.1                                            --
-- Author      : Sigit Dewantor                                 --
-- Address     : VLSI RG, Dept. of Electrical Engineering ITB,  --
--               Bandung, Indonesia                             --
-- E-mail      : sigit@ic.vlsi.itb.ac.id                        --

ENTITY in_key IS
PORT ( clk,rst,key_sended           : IN  BIT;
       en_bufin,req_key,ikey_ready  : OUT BIT;
       n_block                      : OUT BIT;
       vdd, vss                     : IN BIT
      );
END in_key;

ARCHITECTURE fsm OF in_key IS

TYPE STATE_TYPE IS (S0, S1, S2, S3, S4,S5, S6, S7);

-- pragma CLOCK clk
-- pragma CURRENT_STATE CURRENT_STATE
-- pragma NEXT_STATE NEXT_STATE

SIGNAL CURRENT_STATE, NEXT_STATE: STATE_TYPE;

BEGIN
  PROCESS ( CURRENT_STATE, rst)
    BEGIN
      IF ( rst = '1' ) THEN
          NEXT_STATE <= S0;
          req_key <= '1';    
          en_bufin <= '0';
          ikey_ready <= '0';
          n_block  <= '0';
      ELSE
          CASE CURRENT_STATE IS
             WHEN S0 =>
                if(key_sended = '1') then
                   req_key   <= '0';
                   en_bufin <= '1';
                   ikey_ready <= '0';
                   n_block  <= '0';
                   NEXT_STATE <= S1;
                 else
                   req_key   <= '1';
                   en_bufin <= '0';
                   ikey_ready <= '0';
                   n_block  <= '0';     
                   NEXT_STATE <= S0;
                 end if;                             
             WHEN S1 =>                    
                   req_key   <= '1';
                   en_bufin <= '0';
                   ikey_ready <= '0';
                   n_block  <= '1';
                   NEXT_STATE <= S2;                   
             WHEN S2 =>
                if(key_sended = '1') then
                   req_key   <= '0';
                   en_bufin <= '1';
                   ikey_ready <= '0';
                   n_block  <= '1';
                   NEXT_STATE <= S3;
                else
                   req_key   <= '1';
                   en_bufin <= '0';
                   ikey_ready <= '0';
                   n_block  <= '1';     
                   NEXT_STATE <= S2;
                end if;                   
             
            WHEN S3 =>
                   req_key <= '1';
                   en_bufin <= '0';
                   ikey_ready <= '0';
                   n_block <= '1';
                   NEXT_STATE <= S4;
            WHEN S4 =>
                  if(key_sended = '1') then
                        req_key <= '0';
                        en_bufin <= '1';
                        ikey_ready <= '0';
                        n_block <= '1';
                        NEXT_STATE <= S5;
                else
                        req_key <= '1';
                        en_bufin <= '0';
                        ikey_ready <= '0';
                        n_block <= '1';
                        NEXT_STATE <= S4;
                end if;
            WHEN S5 =>
                req_key <= '1';
                en_bufin <= '0';
                ikey_ready <= '0';
                n_block <= '1';
                NEXT_STATE <= S6;

            WHEN S6 =>  
                   req_key   <= '0';
                   en_bufin <= '0';                                
                   ikey_ready <= '1';
                   n_block  <= '0';             
                   NEXT_STATE <= S0;                         
             WHEN OTHERS =>
                ASSERT ( '1' )
                REPORT "Illegal State";

          END CASE;
      END IF;
END PROCESS;

PROCESS (clk)
  BEGIN
    IF ((clk AND NOT clk'STABLE) ='1') THEN
         CURRENT_STATE <= NEXT_STATE;
    END IF;
END PROCESS;

END fsm;