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-- l80pkg.vhdl -- Support package for Light8080 SoC.
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-- l80pkg.vhdl -- Support package for Light8080 SoC.
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--
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--
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-- Contains functions used to initialize internal BRAM with object code.
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-- Contains functions used to initialize internal BRAM with object code.
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--
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--
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-- This package will be used from the object code package where the program
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-- This package will be used from the object code package where the program
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-- initialized RAM constant is defined. If you use script obj2hdl it will
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-- initialized RAM constant is defined. If you use script obj2hdl it will
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-- take care of this for you.
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-- take care of this for you.
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-- The package is used in entity l80soc too, and nowhere else.
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-- The package is used in entity l80soc too, and nowhere else.
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--
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--
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-- This file and all the light8080 project files are freeware (See COPYING.TXT)
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-- This file and all the light8080 project files are freeware (See COPYING.TXT)
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library ieee;
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_unsigned.all;
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package l80pkg is
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package l80pkg is
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-- Basic array type for the declaration of initialization constants.
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-- Basic array type for the declaration of initialization constants.
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-- This type is meant to be used to declare a constant with the object code
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-- This type is meant to be used to declare a constant with the object code
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-- that is to be preprogrammed in an initialized RAM.
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-- that is to be preprogrammed in an initialized RAM.
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type obj_code_t is array(integer range <>) of std_logic_vector(7 downto 0);
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type obj_code_t is array(integer range <>) of std_logic_vector(7 downto 0);
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-- Basic array type for the definition of initialized RAMs.
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-- Basic array type for the definition of initialized RAMs.
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type ram_t is array(integer range <>) of std_logic_vector(7 downto 0);
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type ram_t is array(integer range <>) of std_logic_vector(7 downto 0);
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-- Builds BRAM initialization constant from a constant CONSTRAINED byte array
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-- Builds BRAM initialization constant from a constant CONSTRAINED byte array
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-- containing the application object code.
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-- containing the application object code.
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-- The object code is placed at the beginning of the BRAM and the rest is
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-- The object code is placed at the beginning of the BRAM and the rest is
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-- filled with zeros.
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-- filled with zeros.
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-- CAN BE USED IN SYNTHESIZABLE CODE to compute a BRAM initialization constant
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-- CAN BE USED IN SYNTHESIZABLE CODE to compute a BRAM initialization constant
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-- from a constant argument.
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-- from a constant argument.
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--
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--
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-- oC: Object code table (as generated by utility script obj2hdl for instance).
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-- oC: Object code table (as generated by utility script obj2hdl for instance).
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-- size: Size of the target memory.
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-- size: Size of the target memory.
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-- Returns ram_t value size-bytes long, suitable for synth-time initialization
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-- Returns ram_t value size-bytes long, suitable for synth-time initialization
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-- of a BRAM.
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-- of a BRAM.
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function objcode_to_bram(oC : obj_code_t; size : integer) return ram_t;
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function objcode_to_bram(oC : obj_code_t; size : integer) return ram_t;
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-- Compute log2(A), rounding up.
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-- Use this to get the minimum width of the address bus necessary to
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-- address A locations.
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function log2(A : natural) return natural;
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end package;
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end package;
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package body l80pkg is
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package body l80pkg is
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-- Builds BRAM initialization constant from a constant CONSTRAINED byte array
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-- Builds BRAM initialization constant from a constant CONSTRAINED byte array
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-- containing the application object code.
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-- containing the application object code.
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function objcode_to_bram(oC : obj_code_t; size : integer) return ram_t is
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function objcode_to_bram(oC : obj_code_t; size : integer) return ram_t is
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variable br : ram_t(integer range 0 to size-1);
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variable br : ram_t(integer range 0 to size-1);
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variable i : integer;
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variable i : integer;
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variable obj_size : integer;
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variable obj_size : integer;
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begin
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begin
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-- If the object code table is longer than the array size, truncate code
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-- If the object code table is longer than the array size, truncate code
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if oC'length > size then
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if oC'length > size then
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obj_size := size;
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obj_size := size;
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else
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else
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obj_size := oC'length;
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obj_size := oC'length;
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end if;
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end if;
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-- Copy object code to start of BRAM...
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-- Copy object code to start of BRAM...
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for i in 0 to obj_size-1 loop
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for i in 0 to obj_size-1 loop
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br(i) := oC(i);
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br(i) := oC(i);
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end loop;
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end loop;
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-- ... and fill the rest with zeros
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-- ... and fill the rest with zeros
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br(obj_size to size-1) := (others => x"00");
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br(obj_size to size-1) := (others => x"00");
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return br;
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return br;
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end function objcode_to_bram;
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end function objcode_to_bram;
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function log2(A : natural) return natural is
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begin
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for I in 1 to 30 loop -- Works for up to 32 bit integers
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if(2**I >= A) then
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return(I);
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end if;
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end loop;
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return(30);
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end function log2;
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end package body;
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end package body;
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