-- ------------------------------------------
-- description du status du DLX-m en VHDL -
-- version m0.3
-- 4 decembre 1992
-- ------------------------------------------
--
-- le chemin de test n'est pas implemente, seuls figurent les connecteurs
-- associes  scout, fonc  .
-- Dans la simulation fonc doit etre a 1, scout  doivent etre 
-- mis a zero .


entity dlxm_sts is

port( ck        : in  bit ;                       -- horloge externe
      gel       : in  bit ;                       -- gel externe
      st_datain : in bit_vector(31 downto 0) ;    -- data du d_p pour modif status
      w_sr      : in  bit ;                       -- m_ins(16)=st_datain enable
      reset     : in  bit ;                       -- connecteur externe reset   
      ovr       : in  bit ;                       -- flag calcule dans data_path
      ipc       : in  bit ;                       -- flag calcule dans dpt
      byte      : in  bit ;                       -- ................. controle
      ico       : in  bit ;                       -- ................. controle
      data      : in  bit ;                       -- flag acces memoire ........
      mem       : in  bit ;                       -- ..........................
      it        : in  bit_vector(3 downto 0) ;    -- connecteur externe
      adr01     : in  bit_vector(1 downto 0) ;    -- bits poids faible adr du d_path
      adr31     : in  bit ;                       -- bit ...    fort   ..........
      rqst      : out bit ;                       -- signal int.  masquable 
      excp      : out bit ;                       -- .....  exception non masquable
      --rst       : out bit ;                       -- signal requete reset non masqu.
      st_datout : out bit_vector(31 downto 0) ;   -- registre status mis a jour 
      fonc      : in bit ;
      scout     : out bit ;
      vdd       : in  bit ;
      vss       : in  bit ) ;

end dlxm_sts ;

architecture FONCTIONAL of dlxm_sts is

-- --------------------------
-- - Definition des signaux -
-- --------------------------

signal d_status : reg_vector(31 downto 0) register ;

signal sh_reset : bit ;
signal sh_iav   : bit ;
signal sh_ico   : bit ;
signal sh_dav   : bit ;
signal sh_ovr   : bit ;
signal sh_it    : bit_vector(3 downto 0) ;

-- ----------------------------------
-- - ecriture des shifter du status -
-- ----------------------------------

begin

sh_reset  <= st_datain(3) when (w_sr='1') else
             '1' when (reset='1')      else
             '0' ;

sh_iav  <= st_datain(8) when (w_sr='1') else
             '1' when (ipc='1') else --  ((data='1') and (mem='0') and (adr01/=B"00")) 
             '0' ;
       --(data='1') and (mem='0') and (adr31='1') and (d_status(0)='1')) 

sh_ico  <= st_datain(9) when (w_sr='1') else
           '1' when ( ico ='1') else
           '0';

sh_dav  <= st_datain(10) when (w_sr='1') else
           '1' when (( adr01/= B"00") and (byte='0') and (data='0') and (mem='0')) else
           '1' when (( adr31='1') and (data='0') and (mem='0') and (d_status(0)='1')) else
           '0'  ; 

sh_ovr  <= st_datain(11) when (w_sr='1') else
           '1' when ( ovr='1' )      else
           '0'  ;

sh_it   <= st_datain(15 downto 12) when (w_sr='1') else
           it(3 downto 0) ; 

-- ------------------------------------
-- - ecriture dans les bascules du sr -
-- ------------------------------------
-- reset et exceptions sont dans "pieges a 1" --------------------------
-- ainsi que les interruptions                 
------------------------------------------------------------------------

binactif_sr : block (((not ck) and (not gel))='1' and not ck'STABLE)
begin
 with w_sr select
   d_status(2 downto 0) <= guarded st_datain(2 downto 0) when '1',
                                   d_status(2 downto 0) when others ;
 with w_sr select
   d_status(7 downto 4) <= guarded st_datain(7 downto 4) when '1',
                                   d_status(7 downto 4) when others ;
 with w_sr select
   d_status(31 downto 16) <= guarded st_datain(31 downto 16) when '1',
                                     d_status(31 downto 16) when others;
 with (w_sr & reset) select
   d_status(3) <= guarded d_status(3) when B"00",
                          sh_reset when others;
 with (w_sr & sh_iav) select
   d_status(8) <= guarded d_status(8)  when B"00",
                          sh_iav when others;
 with (w_sr & sh_ico) select
   d_status(9) <= guarded d_status(9) when B"00",
                          sh_ico when others;
 with (w_sr & sh_dav) select
   d_status(10)  <= guarded d_status(10) when B"00",
                            sh_dav when others;
 with (w_sr & sh_ovr) select
   d_status(11)  <= guarded d_status(11) when B"00",
                            sh_ovr when others;
 with (w_sr & sh_it(3)) select
   d_status(15)  <= guarded d_status(15) when B"00",
                            sh_it(3)     when others ;
 with (w_sr & sh_it(2)) select
   d_status(14)  <= guarded d_status(14) when B"00",
                            sh_it(2)     when others ;
 with (w_sr & sh_it(1)) select
   d_status(13)  <= guarded d_status(13) when B"00",
                            sh_it(1)     when others ;
 with (w_sr & sh_it(0)) select
   d_status(12)  <= guarded d_status(12) when B"00",
                            sh_it(0)     when others ;
 end block;

-- --------------------------
-- - definition des sorties -
-- --------------------------
--
-- le chemin de test n est pas implemente ------
--
scout <= '0' ;
--

st_datout (31 downto 0) <= d_status(31 downto 0) ;

rqst <= '1' when ((d_status(15 downto 12)/=B"0000") and (d_status(1)='1')) else
        '0' ;

excp <= '1' when (d_status(11 downto 10)/=B"00") or (d_status(8)/='0')
         else
        '0' ;

--rst <= d_status(3) ;


end FONCTIONAL;