ToolsCourseTp3: am2901_dpt.vbe

ENTITY  am2901_dpt  IS

PORT(
        -- Command for selecting operands R and S.
        ops_mx : in    BIT_VECTOR(2 downto 0);
        opr_mx : in    BIT_VECTOR(1 downto 0);

        -- ALU commands and auxiliary terminals.
        alu_k    : in    BIT_VECTOR(4 downto 0);
        alu_cin  : in    BIT;
        alu_cout :   out BIT;
        alu_over :   inout BIT;

        -- RAM, ACCU shifter commands and auxiliary terminals.
        ram_sh : in    BIT_VECTOR(1 downto 0);
        acc_sh : in    BIT_VECTOR(1 downto 0);
        -- RAM shifter inputs.
        ram_i_up   : in    BIT;
        ram_i_down : in    BIT;
        -- ACCU shifter inputs.
        acc_i_up   : in    BIT; 
        acc_i_down : in    BIT;
        -- ACCU shifter outputs ("acc_scout" is "acc_q_up").
        acc_q_up :   out BIT;
        acc_q_down :   out BIT;

        -- Output multiplexer commnand (for X bus).
        out_mx : in    BIT;

        -- ACCU controls terminals.
        acc_ck    : in    BIT;
        acc_wen   : in    BIT;

        -- Register file controls terminals.
        ram_ck   : in    BIT_VECTOR(15 downto 0) ;  -- Register clocks (ck).
        b_w      : in    BIT_VECTOR(15 downto 0) ;  -- Write enable
        a        : in    BIT_VECTOR(15 downto 0) ;  -- Register A address.
        b        : in    BIT_VECTOR(15 downto 0) ;  -- Register B address.

        -- Data buses terminals.
        opr_d  : in    BIT_VECTOR(3 downto 0);
        alu_f  : inout BIT_VECTOR(3 downto 0);
        alu_np :   out BIT_VECTOR(3 downto 0);
        alu_ng :   out BIT_VECTOR(3 downto 0);
        out_x  :   out BIT_VECTOR(3 downto 0);

        -- Power supply connectors.
        vdd : in   BIT;
        vss : in   BIT
        );

END am2901_dpt;


ARCHITECTURE  behavior_data_flow  OF  am2901_dpt  IS

        -- Internals bus.
        SIGNAL ops_ns : BIT_VECTOR(3 downto 0);
        SIGNAL opr_nr : BIT_VECTOR(3 downto 0);
        SIGNAL ram_d  : BIT_VECTOR(3 downto 0);
        SIGNAL acc_d  : BIT_VECTOR(3 downto 0);

        -- Internal registers.
        -- ACCU master/slave.
        SIGNAL acc_s_q   : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL acc_m_q   : REG_VECTOR(3 downto 0) REGISTER;
        -- Internal ACCU clock signals.
        SIGNAL acc_ws  : BIT;
        -- RAM SIGNALS
        SIGNAL ram_adra  : BIT_VECTOR(15 DOWNTO 0);
        SIGNAL ram_adrb  : BIT_VECTOR(15 DOWNTO 0);
        -- RAM masters.
        SIGNAL ram_m_r0  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r1  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r2  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r3  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r4  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r5  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r6  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r7  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r8  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r9  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r10 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r11 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r12 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r13 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r14 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_m_r15 : REG_VECTOR(3 downto 0) REGISTER;
        -- RAM slaves.
        SIGNAL ram_s_r0  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r1  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r2  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r3  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r4  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r5  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r6  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r7  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r8  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r9  : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r10 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r11 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r12 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r13 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r14 : REG_VECTOR(3 downto 0) REGISTER;
        SIGNAL ram_s_r15 : REG_VECTOR(3 downto 0) REGISTER;
        -- Internal RAM clocks signals.
        -- Masters write enable.
        SIGNAL ram_wmd0  :BIT;
        SIGNAL ram_wmd1  :BIT;
        SIGNAL ram_wmd2  :BIT;
        SIGNAL ram_wmd3  :BIT;
        SIGNAL ram_wmd4  :BIT;
        SIGNAL ram_wmd5  :BIT;
        SIGNAL ram_wmd6  :BIT;
        SIGNAL ram_wmd7  :BIT;
        SIGNAL ram_wmd8  :BIT;
        SIGNAL ram_wmd9  :BIT;
        SIGNAL ram_wmd10 :BIT;
        SIGNAL ram_wmd11 :BIT;
        SIGNAL ram_wmd12 :BIT;
        SIGNAL ram_wmd13 :BIT;
        SIGNAL ram_wmd14 :BIT;
        SIGNAL ram_wmd15 :BIT;
        -- Slaves write enable.
        SIGNAL ram_ws0  :BIT;
        SIGNAL ram_ws1  :BIT;
        SIGNAL ram_ws2  :BIT;
        SIGNAL ram_ws3  :BIT;
        SIGNAL ram_ws4  :BIT;
        SIGNAL ram_ws5  :BIT;
        SIGNAL ram_ws6  :BIT;
        SIGNAL ram_ws7  :BIT;
        SIGNAL ram_ws8  :BIT;
        SIGNAL ram_ws9  :BIT;
        SIGNAL ram_ws10 :BIT;
        SIGNAL ram_ws11 :BIT;
        SIGNAL ram_ws12 :BIT;
        SIGNAL ram_ws13 :BIT;
        SIGNAL ram_ws14 :BIT;
        SIGNAL ram_ws15 :BIT;
        -- Output mux bus RA and RB.
        SIGNAL ram_ra  : MUX_VECTOR(3 downto 0) BUS;
        SIGNAL ram_rb  : MUX_VECTOR(3 downto 0) BUS;
        -- Internal ALU signals.
        SIGNAL alu_cry : BIT_VECTOR(4 downto 0);
        SIGNAL alu_s   : BIT_VECTOR(3 downto 0);
        SIGNAL alu_r   : BIT_VECTOR(3 downto 0);



        SIGNAL sig_acc : BIT_VECTOR(3 downto 0);

        SIGNAL sig_ram0  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram1  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram2  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram3  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram4  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram5  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram6  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram7  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram8  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram9  : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram10 : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram11 : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram12 : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram13 : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram14 : BIT_VECTOR(3 downto 0);
        SIGNAL sig_ram15 : BIT_VECTOR(3 downto 0);

        SIGNAL ram_ck0  :BIT;
        SIGNAL ram_ck1  :BIT;
        SIGNAL ram_ck2  :BIT;
        SIGNAL ram_ck3  :BIT;
        SIGNAL ram_ck4  :BIT;
        SIGNAL ram_ck5  :BIT;
        SIGNAL ram_ck6  :BIT;
        SIGNAL ram_ck7  :BIT;
        SIGNAL ram_ck8  :BIT;
        SIGNAL ram_ck9  :BIT;
        SIGNAL ram_ck10 :BIT;
        SIGNAL ram_ck11 :BIT;
        SIGNAL ram_ck12 :BIT;
        SIGNAL ram_ck13 :BIT;
        SIGNAL ram_ck14 :BIT;
        SIGNAL ram_ck15 :BIT;

BEGIN

        -- ******************* RAM shifter description *******************

        -- RAM shifter control code :
        --     1)                "00" : UP   shift.
        --     2)                "01" : DOWN shift.
        --     3) either "10" or "11" : NO   shift.
        WITH  ram_sh(1 downto 0)  SELECT
                ram_d <= alu_f(2 downto 0)&ram_i_down  WHEN  B"00",
                         ram_i_up&alu_f(3 downto 1)    WHEN  B"01",
                         alu_f(3 downto 0)             WHEN  B"10" | B"11";

        -- ****************** ACCU shifter description *******************
        acc_q_down <= acc_s_q(0);

        -- ACCU shifter control code :
        --     1)                "00" : UP   shift accu.
        --     2)                "01" : DOWN shift accu.
        --     3) either "10" or "11" : write accu with no shift.
        WITH  acc_sh(1 downto 0)  SELECT
                acc_d <=  acc_s_q(2 downto 0)&acc_i_down  WHEN  B"00",
                          acc_i_up&acc_s_q(3 downto 1)    WHEN  B"01",
                          alu_f(3 downto 0)               WHEN  B"10" | B"11";

        -- ****************** S multiplexer description ******************
        WITH  ops_mx(2 downto 0)  SELECT
                ops_ns <= not acc_s_q   WHEN  B"000",
                          not ram_rb    WHEN  B"001",
                          not ram_ra    WHEN  B"010" | B"011",
                          "1111"        WHEN  B"100" | B"101" | B"110" | B"111";

        -- ****************** R multiplexer description ******************
        WITH  opr_mx(1 downto 0)  SELECT
                opr_nr <= not ram_ra  WHEN  B"00",
                          not opr_d   WHEN  B"01",
                          "1111"      WHEN  B"10" | B"11";

        -- ****************** X multiplexer description ******************
        WITH  out_mx  SELECT
                out_x <= alu_f WHEN  B"0",
                         ram_ra  WHEN  B"1";

        -- *********************** ALU description ***********************
        alu_cry(0) <= alu_cin;
        alu_cout   <= alu_cry(4);
        alu_over   <= alu_cry(3);

        -- Inversion of R and S operands.
        alu_s <= not ops_ns WHEN alu_k(1) = '0' ELSE ops_ns;
        alu_r <= not opr_nr WHEN alu_k(0) = '0' ELSE opr_nr;

        -- Compute of nP and nG.
        alu_np <= not (alu_s  or alu_r);
        alu_ng <= not (alu_s and alu_r);

        -- Arithmetic adder description.
        alu_cry(4 downto 1) <= (alu_s and alu_r )
                            or (alu_s and alu_cry(3 downto 0))
                            or (alu_cry(3 downto 0) and alu_r);

        -- Select the ALU output.
        WITH  alu_k(4 downto 2)  SELECT
                alu_f <= alu_s xor alu_r  xor alu_cry(3 downto 0) WHEN B"000",
                        (alu_s  or alu_r) xor alu_cry(3 downto 0) WHEN B"001",
                        (alu_s and alu_r) xor alu_cry(3 downto 0) WHEN B"010",
                        alu_cry(3 downto 0)                       WHEN B"011",
                        not (alu_s xor alu_r)                     WHEN B"100",
                        not (alu_s  or alu_r)                     WHEN B"101",
                        not (alu_s and alu_r)                     WHEN B"110",
                        B"1111"                                   WHEN B"111";

        -- ********************** ACCU description ************************
        -- Modification tenant compte du front montant de l'horloge
        acc_ws    <= not acc_ck;
        acc_q_up  <=     acc_s_q(3);

        WITH acc_wen SELECT
            sig_acc <= acc_d   WHEN B"1"  , -- Mode normal
                       acc_s_q WHEN OTHERS ; -- Reprise du registre

        -- A chaque cycle, on ecrit dans acc_s_q
       
        -- Echantillonnage lorsque ck=0 et memorisation sur front montant
        acc_ck:BLOCK(acc_ws = '1')
        BEGIN
             acc_m_q <= GUARDED sig_acc;
        END BLOCK acc_ck;

        -- Slave register write.
        -- Echantillonnage lorsque ck=1 et memorisation sur front descendant
        acc_ws:BLOCK(acc_ck = '1')
        BEGIN
                acc_s_q <= GUARDED acc_m_q;
        END BLOCK acc_ws;

        -- *********************** RAM description ***********************

        -- Select B register.
        ram_adrb(0 ) <= b(0 ) ;
        ram_adrb(1 ) <= b(1 ) ;
        ram_adrb(2 ) <= b(2 ) ;
        ram_adrb(3 ) <= b(3 ) ;
        ram_adrb(4 ) <= b(4 ) ;
        ram_adrb(5 ) <= b(5 ) ;
        ram_adrb(6 ) <= b(6 ) ;
        ram_adrb(7 ) <= b(7 ) ;
        ram_adrb(8 ) <= b(8 ) ;
        ram_adrb(9 ) <= b(9 ) ;
        ram_adrb(10) <= b(10) ;
        ram_adrb(11) <= b(11) ;
        ram_adrb(12) <= b(12) ;
        ram_adrb(13) <= b(13) ;
        ram_adrb(14) <= b(14) ;
        ram_adrb(15) <= b(15) ;
         
        -- Select A register.
        ram_adra(0 ) <= a(0 ) ;
        ram_adra(1 ) <= a(1 ) ;
        ram_adra(2 ) <= a(2 ) ;
        ram_adra(3 ) <= a(3 ) ;
        ram_adra(4 ) <= a(4 ) ;
        ram_adra(5 ) <= a(5 ) ;
        ram_adra(6 ) <= a(6 ) ;
        ram_adra(7 ) <= a(7 ) ;
        ram_adra(8 ) <= a(8 ) ;
        ram_adra(9 ) <= a(9 ) ;
        ram_adra(10) <= a(10) ;
        ram_adra(11) <= a(11) ;
        ram_adra(12) <= a(12) ;
        ram_adra(13) <= a(13) ;
        ram_adra(14) <= a(14) ;
        ram_adra(15) <= a(15) ;

        -- Write master enable signals for b
        ram_wmd0  <= b_w(0 );
        ram_wmd1  <= b_w(1 );
        ram_wmd2  <= b_w(2 );
        ram_wmd3  <= b_w(3 );
        ram_wmd4  <= b_w(4 );
        ram_wmd5  <= b_w(5 );
        ram_wmd6  <= b_w(6 );
        ram_wmd7  <= b_w(7 );
        ram_wmd8  <= b_w(8 );
        ram_wmd9  <= b_w(9 );
        ram_wmd10 <= b_w(10);
        ram_wmd11 <= b_w(11);
        ram_wmd12 <= b_w(12);
        ram_wmd13 <= b_w(13);
        ram_wmd14 <= b_w(14);
        ram_wmd15 <= b_w(15);

        -- Write slave enable signals.
        ram_ws0  <= not ram_ck(0 ) ;
        ram_ws1  <= not ram_ck(1 ) ;
        ram_ws2  <= not ram_ck(2 ) ;
        ram_ws3  <= not ram_ck(3 ) ;
        ram_ws4  <= not ram_ck(4 ) ;
        ram_ws5  <= not ram_ck(5 ) ;
        ram_ws6  <= not ram_ck(6 ) ;
        ram_ws7  <= not ram_ck(7 ) ;
        ram_ws8  <= not ram_ck(8 ) ;
        ram_ws9  <= not ram_ck(9 ) ;
        ram_ws10 <= not ram_ck(10) ;
        ram_ws11 <= not ram_ck(11) ;
        ram_ws12 <= not ram_ck(12) ;
        ram_ws13 <= not ram_ck(13) ;
        ram_ws14 <= not ram_ck(14) ;
        ram_ws15 <= not ram_ck(15) ;

        ram_ck0  <= ram_ck(0 ) ;
        ram_ck1  <= ram_ck(1 ) ;
        ram_ck2  <= ram_ck(2 ) ;
        ram_ck3  <= ram_ck(3 ) ;
        ram_ck4  <= ram_ck(4 ) ;
        ram_ck5  <= ram_ck(5 ) ;
        ram_ck6  <= ram_ck(6 ) ;
        ram_ck7  <= ram_ck(7 ) ;
        ram_ck8  <= ram_ck(8 ) ;
        ram_ck9  <= ram_ck(9 ) ;
        ram_ck10 <= ram_ck(10) ;
        ram_ck11 <= ram_ck(11) ;
        ram_ck12 <= ram_ck(12) ;
        ram_ck13 <= ram_ck(13) ;
        ram_ck14 <= ram_ck(14) ;
        ram_ck15 <= ram_ck(15) ;


        WITH ram_wmd0  SELECT
            sig_ram0   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r0  WHEN OTHERS ;

        WITH ram_wmd1  SELECT
            sig_ram1   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r1  WHEN OTHERS ;

        WITH ram_wmd2  SELECT
            sig_ram2   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r2  WHEN OTHERS ;

        WITH ram_wmd3 SELECT
            sig_ram3   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r3  WHEN OTHERS ;

        WITH ram_wmd4 SELECT
            sig_ram4   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r4  WHEN OTHERS ;

        WITH ram_wmd5 SELECT
            sig_ram5   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r5  WHEN OTHERS ;

        WITH ram_wmd6 SELECT
            sig_ram6   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r6  WHEN OTHERS ;

        WITH ram_wmd7 SELECT
            sig_ram7   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r7  WHEN OTHERS ;

        WITH ram_wmd8 SELECT
            sig_ram8   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r8  WHEN OTHERS ;

        WITH ram_wmd9 SELECT
            sig_ram9   <= ram_d     WHEN B"1"   , -- Mode ecriture
                          ram_s_r9  WHEN OTHERS ;

        WITH ram_wmd10 SELECT
            sig_ram10  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r10  WHEN OTHERS ;

        WITH ram_wmd11 SELECT
            sig_ram11  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r11  WHEN OTHERS ;

        WITH ram_wmd12 SELECT
            sig_ram12  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r12  WHEN OTHERS ;

        WITH ram_wmd13 SELECT
            sig_ram13  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r13  WHEN OTHERS ;

        WITH ram_wmd14 SELECT
            sig_ram14  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r14  WHEN OTHERS ;

        WITH ram_wmd15 SELECT
            sig_ram15  <= ram_d      WHEN B"1"   , -- Mode ecriture
                          ram_s_r15  WHEN OTHERS ;

        -- Write registers description.

        -- Echantillonnage lorsque ck=0 et memorisation sur front montant
        wm0 :BLOCK(ram_ws0 = '1') BEGIN ram_m_r0  <= GUARDED sig_ram0  ; END BLOCK wm0 ;
        wm1 :BLOCK(ram_ws1 = '1') BEGIN ram_m_r1  <= GUARDED sig_ram1  ; END BLOCK wm1 ;
        wm2 :BLOCK(ram_ws2 = '1') BEGIN ram_m_r2  <= GUARDED sig_ram2  ; END BLOCK wm2 ;
        wm3 :BLOCK(ram_ws3 = '1') BEGIN ram_m_r3  <= GUARDED sig_ram3  ; END BLOCK wm3 ;
        wm4 :BLOCK(ram_ws4 = '1') BEGIN ram_m_r4  <= GUARDED sig_ram4  ; END BLOCK wm4 ;
        wm5 :BLOCK(ram_ws5 = '1') BEGIN ram_m_r5  <= GUARDED sig_ram5  ; END BLOCK wm5 ;
        wm6 :BLOCK(ram_ws6 = '1') BEGIN ram_m_r6  <= GUARDED sig_ram6  ; END BLOCK wm6 ;
        wm7 :BLOCK(ram_ws7 = '1') BEGIN ram_m_r7  <= GUARDED sig_ram7  ; END BLOCK wm7 ;
        wm8 :BLOCK(ram_ws8 = '1') BEGIN ram_m_r8  <= GUARDED sig_ram8  ; END BLOCK wm8 ;
        wm9 :BLOCK(ram_ws9 = '1') BEGIN ram_m_r9  <= GUARDED sig_ram9  ; END BLOCK wm9 ;
        wm10:BLOCK(ram_ws10 = '1') BEGIN ram_m_r10 <= GUARDED sig_ram10 ; END BLOCK wm10;
        wm11:BLOCK(ram_ws11 = '1') BEGIN ram_m_r11 <= GUARDED sig_ram11 ; END BLOCK wm11;
        wm12:BLOCK(ram_ws12 = '1') BEGIN ram_m_r12 <= GUARDED sig_ram12 ; END BLOCK wm12;
        wm13:BLOCK(ram_ws13 = '1') BEGIN ram_m_r13 <= GUARDED sig_ram13 ; END BLOCK wm13;
        wm14:BLOCK(ram_ws14 = '1') BEGIN ram_m_r14 <= GUARDED sig_ram14 ; END BLOCK wm14;
        wm15:BLOCK(ram_ws15 = '1') BEGIN ram_m_r15 <= GUARDED sig_ram15 ; END BLOCK wm15;
        
        -- Write slave registers description.
        -- Echantillonnage lorsque ck=1 et memorisation sur front descendant
        ws0 :BLOCK(ram_ck0 = '1') BEGIN ram_s_r0  <= GUARDED ram_m_r0 ; END BLOCK ws0 ;
        ws1 :BLOCK(ram_ck1 = '1') BEGIN ram_s_r1  <= GUARDED ram_m_r1 ; END BLOCK ws1 ;
        ws2 :BLOCK(ram_ck2 = '1') BEGIN ram_s_r2  <= GUARDED ram_m_r2 ; END BLOCK ws2 ;
        ws3 :BLOCK(ram_ck3 = '1') BEGIN ram_s_r3  <= GUARDED ram_m_r3 ; END BLOCK ws3 ;
        ws4 :BLOCK(ram_ck4 = '1') BEGIN ram_s_r4  <= GUARDED ram_m_r4 ; END BLOCK ws4 ;
        ws5 :BLOCK(ram_ck5 = '1') BEGIN ram_s_r5  <= GUARDED ram_m_r5 ; END BLOCK ws5 ;
        ws6 :BLOCK(ram_ck6 = '1') BEGIN ram_s_r6  <= GUARDED ram_m_r6 ; END BLOCK ws6 ;
        ws7 :BLOCK(ram_ck7 = '1') BEGIN ram_s_r7  <= GUARDED ram_m_r7 ; END BLOCK ws7 ;
        ws8 :BLOCK(ram_ck8 = '1') BEGIN ram_s_r8  <= GUARDED ram_m_r8 ; END BLOCK ws8 ;
        ws9 :BLOCK(ram_ck9 = '1') BEGIN ram_s_r9  <= GUARDED ram_m_r9 ; END BLOCK ws9 ;
        ws10:BLOCK(ram_ck10 = '1') BEGIN ram_s_r10 <= GUARDED ram_m_r10; END BLOCK ws10;
        ws11:BLOCK(ram_ck11 = '1') BEGIN ram_s_r11 <= GUARDED ram_m_r11; END BLOCK ws11;
        ws12:BLOCK(ram_ck12 = '1') BEGIN ram_s_r12 <= GUARDED ram_m_r12; END BLOCK ws12;
        ws13:BLOCK(ram_ck13 = '1') BEGIN ram_s_r13 <= GUARDED ram_m_r13; END BLOCK ws13;
        ws14:BLOCK(ram_ck14 = '1') BEGIN ram_s_r14 <= GUARDED ram_m_r14; END BLOCK ws14;
        ws15:BLOCK(ram_ck15 = '1') BEGIN ram_s_r15 <= GUARDED ram_m_r15; END BLOCK ws15;
        
        -- Select register to write on tristate bus RA.
        wa0 :BLOCK(ram_adra(0 )) BEGIN ram_ra <= GUARDED ram_s_r0 ; END BLOCK wa0 ;
        wa1 :BLOCK(ram_adra(1 )) BEGIN ram_ra <= GUARDED ram_s_r1 ; END BLOCK wa1 ;
        wa2 :BLOCK(ram_adra(2 )) BEGIN ram_ra <= GUARDED ram_s_r2 ; END BLOCK wa2 ;
        wa3 :BLOCK(ram_adra(3 )) BEGIN ram_ra <= GUARDED ram_s_r3 ; END BLOCK wa3 ;
        wa4 :BLOCK(ram_adra(4 )) BEGIN ram_ra <= GUARDED ram_s_r4 ; END BLOCK wa4 ;
        wa5 :BLOCK(ram_adra(5 )) BEGIN ram_ra <= GUARDED ram_s_r5 ; END BLOCK wa5 ;
        wa6 :BLOCK(ram_adra(6 )) BEGIN ram_ra <= GUARDED ram_s_r6 ; END BLOCK wa6 ;
        wa7 :BLOCK(ram_adra(7 )) BEGIN ram_ra <= GUARDED ram_s_r7 ; END BLOCK wa7 ;
        wa8 :BLOCK(ram_adra(8 )) BEGIN ram_ra <= GUARDED ram_s_r8 ; END BLOCK wa8 ;
        wa9 :BLOCK(ram_adra(9 )) BEGIN ram_ra <= GUARDED ram_s_r9 ; END BLOCK wa9 ;
        wa10:BLOCK(ram_adra(10)) BEGIN ram_ra <= GUARDED ram_s_r10; END BLOCK wa10;
        wa11:BLOCK(ram_adra(11)) BEGIN ram_ra <= GUARDED ram_s_r11; END BLOCK wa11;
        wa12:BLOCK(ram_adra(12)) BEGIN ram_ra <= GUARDED ram_s_r12; END BLOCK wa12;
        wa13:BLOCK(ram_adra(13)) BEGIN ram_ra <= GUARDED ram_s_r13; END BLOCK wa13;
        wa14:BLOCK(ram_adra(14)) BEGIN ram_ra <= GUARDED ram_s_r14; END BLOCK wa14;
        wa15:BLOCK(ram_adra(15)) BEGIN ram_ra <= GUARDED ram_s_r15; END BLOCK wa15;
        
        -- Select register to write on tristate bus RB.
        wb0 :BLOCK(ram_adrb(0 )) BEGIN ram_rb <= GUARDED ram_s_r0 ; END BLOCK wb0 ;
        wb1 :BLOCK(ram_adrb(1 )) BEGIN ram_rb <= GUARDED ram_s_r1 ; END BLOCK wb1 ;
        wb2 :BLOCK(ram_adrb(2 )) BEGIN ram_rb <= GUARDED ram_s_r2 ; END BLOCK wb2 ;
        wb3 :BLOCK(ram_adrb(3 )) BEGIN ram_rb <= GUARDED ram_s_r3 ; END BLOCK wb3 ;
        wb4 :BLOCK(ram_adrb(4 )) BEGIN ram_rb <= GUARDED ram_s_r4 ; END BLOCK wb4 ;
        wb5 :BLOCK(ram_adrb(5 )) BEGIN ram_rb <= GUARDED ram_s_r5 ; END BLOCK wb5 ;
        wb6 :BLOCK(ram_adrb(6 )) BEGIN ram_rb <= GUARDED ram_s_r6 ; END BLOCK wb6 ;
        wb7 :BLOCK(ram_adrb(7 )) BEGIN ram_rb <= GUARDED ram_s_r7 ; END BLOCK wb7 ;
        wb8 :BLOCK(ram_adrb(8 )) BEGIN ram_rb <= GUARDED ram_s_r8 ; END BLOCK wb8 ;
        wb9 :BLOCK(ram_adrb(9 )) BEGIN ram_rb <= GUARDED ram_s_r9 ; END BLOCK wb9 ;
        wb10:BLOCK(ram_adrb(10)) BEGIN ram_rb <= GUARDED ram_s_r10; END BLOCK wb10;
        wb11:BLOCK(ram_adrb(11)) BEGIN ram_rb <= GUARDED ram_s_r11; END BLOCK wb11;
        wb12:BLOCK(ram_adrb(12)) BEGIN ram_rb <= GUARDED ram_s_r12; END BLOCK wb12;
        wb13:BLOCK(ram_adrb(13)) BEGIN ram_rb <= GUARDED ram_s_r13; END BLOCK wb13;
        wb14:BLOCK(ram_adrb(14)) BEGIN ram_rb <= GUARDED ram_s_r14; END BLOCK wb14;
        wb15:BLOCK(ram_adrb(15)) BEGIN ram_rb <= GUARDED ram_s_r15; END BLOCK wb15;

        -- ********************* Power supply check **********************
        ASSERT(vss = '0')
                REPORT "Power supply VSS badly connected." SEVERITY WARNING;
        ASSERT(vdd = '1')
                REPORT "Power supply VDD badly connected." SEVERITY WARNING;

END  behavior_data_flow;