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--------------------------------------------------------------------------------
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-- mips_pkg.vhdl -- Configuration constants & utility types and functions
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--------------------------------------------------------------------------------
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-- IMPORTANT:
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-- Here's where you define the memory map of the system, in the implementation
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-- of function decode_addr.
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-- You need to change that function to change the memory map, independent of any
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-- additional address decoding you may do out of the FPGA (e.g. if you have more
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-- than one chip on any data bus) or out of the MCU module (e.g. when you add
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-- new IO registers).
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-- Please see the module c2sb_demo and mips_mcu for examples of memory decoding.
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--------------------------------------------------------------------------------
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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 mips_pkg is
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package mips_pkg is
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-- FIXME this stuff belongs in the cache module where address decoding is made
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---- Basic types ---------------------------------------------------------------
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-- (besides, they should be module generics, not package constants)
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subtype t_word is std_logic_vector(31 downto 0);
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---- System configuration constants --------------------------------------------
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-- True to use standard-ish MIPS-1 memory map, false to use Plasma's
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-- (see implementation of function decode_addr below).
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constant USE_MIPS1_ADDR_MAP : boolean := true;
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-- Reset vector address minus 4 (0xfffffffc for Plasma, 0xbfbffffc for mips1)
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constant RESET_VECTOR_M4 : t_word := X"bfbffffc";
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-- Trap vector address (0x0000003c for Plasma, 0xbfc00180 for mips1)
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constant TRAP_VECTOR : t_word := X"bfc00180";
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---- Address decoding ----------------------------------------------------------
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-- Note: it is the cache module that does all internal address decoding --------
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-- This is the slice of the address that will be used to decode memory areas
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subtype t_addr_decode is std_logic_vector(31 downto 24);
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subtype t_addr_decode is std_logic_vector(31 downto 24);
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constant ADDR_BOOT : t_addr_decode := X"00";
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constant ADDR_XRAM : t_addr_decode := X"80";
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-- 'Attributes' of some memory block -- used when decoding memory addresses
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constant ADDR_IO : t_addr_decode := X"20";
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-- type[3] : can_write[1] : cacheable[1] : delay_states[2]
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subtype t_range_attr is std_logic_vector(6 downto 0);
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-- Part of the memory area attribute: the type of memory determines how the
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-- cache module handles each block
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subtype t_memory_type is std_logic_vector(2 downto 0);
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-- These are all the types the cache knows about
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constant MT_BRAM : t_memory_type := "000";
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constant MT_IO_SYNC : t_memory_type := "001";
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constant MT_SRAM_16B : t_memory_type := "010";
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constant MT_FLASH_16B : t_memory_type := "011";
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constant MT_DDR_16B : t_memory_type := "100";
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constant MT_UNMAPPED : t_memory_type := "111";
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---- More basic types and constants --------------------------------------------
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subtype t_addr is std_logic_vector(31 downto 0);
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subtype t_addr is std_logic_vector(31 downto 0);
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subtype t_word is std_logic_vector(31 downto 0);
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subtype t_dword is std_logic_vector(63 downto 0);
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subtype t_dword is std_logic_vector(63 downto 0);
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subtype t_regnum is std_logic_vector(4 downto 0);
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subtype t_regnum is std_logic_vector(4 downto 0);
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type t_rbank is array(0 to 31) of t_word;
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type t_rbank is array(0 to 31) of t_word;
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subtype t_pc is std_logic_vector(31 downto 2);
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subtype t_pc is std_logic_vector(31 downto 2);
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-- This is used as a textual shortcut only
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constant ZERO : t_word := (others => '0');
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constant ZERO : t_word := (others => '0');
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-- control word for ALU
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type t_alu_control is record
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type t_alu_control is record
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logic_sel : std_logic_vector(1 downto 0);
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logic_sel : std_logic_vector(1 downto 0);
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shift_sel : std_logic_vector(1 downto 0);
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shift_sel : std_logic_vector(1 downto 0);
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shift_amount : std_logic_vector(4 downto 0);
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shift_amount : std_logic_vector(4 downto 0);
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neg_sel : std_logic_vector(1 downto 0);
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neg_sel : std_logic_vector(1 downto 0);
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use_logic : std_logic_vector(1 downto 0);
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use_logic : std_logic_vector(1 downto 0);
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cy_in : std_logic;
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cy_in : std_logic;
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use_slt : std_logic;
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use_slt : std_logic;
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arith_unsigned : std_logic;
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arith_unsigned : std_logic;
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end record t_alu_control;
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end record t_alu_control;
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-- Flags coming from the ALU
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type t_alu_flags is record
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type t_alu_flags is record
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inp1_lt_zero : std_logic;
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inp1_lt_zero : std_logic;
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inp1_eq_zero : std_logic;
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inp1_eq_zero : std_logic;
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inp1_lt_inp2 : std_logic;
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inp1_lt_inp2 : std_logic;
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inp1_eq_inp2 : std_logic;
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inp1_eq_inp2 : std_logic;
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-- Computes ceil(log2(A)), e.g. address width of memory block
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-- Computes ceil(log2(A)), e.g. address width of memory block
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-- CAN BE USED IN SYNTHESIZABLE CODE as long as called with constant arguments
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-- CAN BE USED IN SYNTHESIZABLE CODE as long as called with constant arguments
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function log2(A : natural) return natural;
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function log2(A : natural) return natural;
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-- Decodes a memory address, gives the type of memory
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-- CAN BE USED IN SYNTHESIZABLE CODE, argument does not need to be constant
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function decode_addr(addr : t_addr_decode) return t_range_attr;
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end package;
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end package;
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package body mips_pkg is
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package body mips_pkg is
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end if;
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end if;
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end loop;
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end loop;
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return(30);
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return(30);
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end function log2;
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end function log2;
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-- Address decoding for Plasma-like system
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function decode_addr_plasma(addr : t_addr_decode) return t_range_attr is
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begin
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case addr(31 downto 27) is
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when "00000" => return MT_BRAM &"0"&"0"&"00"; -- useg
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when "10000" => return MT_SRAM_16B &"1"&"1"&"00"; -- kseg0
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when "00100" => return MT_IO_SYNC &"1"&"0"&"00"; -- kseg1 i/o
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when others => return MT_UNMAPPED &"0"&"0"&"00"; -- stray
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end case;
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end function decode_addr_plasma;
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-- Address decoding for MIPS-I-like system
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function decode_addr_mips1(addr : t_addr_decode) return t_range_attr is
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begin
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case addr(31 downto 27) is
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when "00000" => return MT_SRAM_16B &"1"&"1"&"00"; -- useg
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when "10000" => return MT_SRAM_16B &"1"&"1"&"00"; -- kseg0
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--when "10100" => return MT_IO_SYNC &"1"&"0"&"00"; -- kseg1 i/o
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when "00100" => return MT_IO_SYNC &"1"&"0"&"00"; -- kseg1 i/o
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when "10110" => return MT_FLASH_16B&"0"&"0"&"10"; -- kseg1 flash
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when "10111" => return MT_BRAM &"0"&"0"&"00"; -- kseg1 boot rom
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when others => return MT_UNMAPPED &"0"&"0"&"00"; -- stray
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end case;
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end function decode_addr_mips1;
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function decode_addr(addr : t_addr_decode) return t_range_attr is
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begin
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if USE_MIPS1_ADDR_MAP then
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return decode_addr_mips1(addr);
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else
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return decode_addr_plasma(addr);
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end if;
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end function decode_addr;
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end package body;
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end package body;
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