--
--
--                                   DISCLAIMER
--
--        This code is the sole property of the Institute for Technology
--        Development (ITD), Jackson, Mississippi, and is distributed for
--        the purpose of providing examples of VHDL models written to
--        modeling standards.  This code may not be used for commercial
--        purposes, and may not be redistributed without permission from
--        the Institute for Technology Development.  ITD assumes no 
--        responsibility for errors, omissions, uses made, or decisions
--        based on its use.  No warranties, expressed or implied, are given.
--
--        ------------------------------------------------------------------

architecture behavioral of SN5438 is

-- ARCHITECTURE DECLARATIVE REGION

    constant generic_loads   : loads := 
        (tld_P3,
         tld_P6,
         tld_P8,
         tld_P11) ;

    constant generic_times   : times := 
        (tplz,
         tpzl) ;

    constant model_times     : sim_timing := 
        get_timing(generic_loads,generic_times) ;

    -- Local signal declarations

    signal ain1,ain2,ain3,ain4            : logic_mv := 'U' ;
    signal bin1,bin2,bin3,bin4            : logic_mv := 'U' ;
    signal yout1,yout2,yout3,yout4        : logic_mv := 'U' ;

-- ARCHITECTURE FUNCTIONAL REGION

begin

    -- assign pin values to internal signals after wire delay

    ain1 <= transport A1 after twd_P1 ;
    bin1 <= transport B1 after twd_P2 ;
    ain2 <= transport A2 after twd_P4 ;
    bin2 <= transport B2 after twd_P5 ;
    ain3 <= transport A3 after twd_P9 ;
    bin3 <= transport B3 after twd_P10 ;
    ain4 <= transport A4 after twd_P12 ;
    bin4 <= transport B4 after twd_P13 ;

    -- Assign internal values to output pins

    Y1 <= yout1 ;
    Y2 <= yout2 ;
    Y3 <= yout3 ;
    Y4 <= yout4 ;

-------------------------------------------------------------------------

NAND1 : process (ain1,bin1)

    variable output_value : logic_mv ;

begin

    output_value := ain1 NAND bin1 ;

    case output_value is
    when '0' =>
        yout1 <= transport '0' after model_times.prop_delays.tpzl_a_b_y ;
    when '1' => 
        yout1 <= transport 'Z' after model_times.prop_delays.tplz_a_b_y ;
    when others =>
        yout1 <= output_value ;
    end case ;

end process NAND1 ;
-------------------------------------------------------------------------

NAND2 : process (ain2,bin2)

    variable output_value : logic_mv ;

begin

    output_value := ain2 NAND bin2 ;

    case output_value is
    when '0' =>
        yout2 <= transport '0' after model_times.prop_delays.tpzl_a_b_y ;
    when '1' => 
        yout2 <= transport 'Z' after model_times.prop_delays.tplz_a_b_y ;
    when others =>
        yout2 <= output_value ;
    end case ;

end process NAND2 ;
-------------------------------------------------------------------------

NAND3 : process (ain3,bin3)

    variable output_value : logic_mv ;

begin

    output_value := ain3 NAND bin3 ;

    case output_value is
    when '0' =>
        yout3 <= transport '0' after model_times.prop_delays.tpzl_a_b_y ;
    when '1' => 
        yout3 <= transport 'Z' after model_times.prop_delays.tplz_a_b_y ;
    when others =>
        yout3 <= output_value ;
    end case ;

end process NAND3 ;
-------------------------------------------------------------------------

NAND4 : process (ain4,bin4)

    variable output_value : logic_mv ;

begin

    output_value := ain4 NAND bin4 ;

    case output_value is
    when '0' =>
        yout4 <= transport '0' after model_times.prop_delays.tpzl_a_b_y ;
    when '1' => 
        yout4 <= transport 'Z' after model_times.prop_delays.tplz_a_b_y ;
    when others =>
        yout4 <= output_value ;
    end case ;

end process NAND4 ;

end behavioral ;