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[/] [ion/] [trunk/] [vhdl/] [mips_pkg.vhdl] - Rev 80
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-------------------------------------------------------------------------------- -- mips_pkg.vhdl -- Configuration constants & utility types and functions -------------------------------------------------------------------------------- -- IMPORTANT: -- Here's where you define the memory map of the system, in the implementation -- of function decode_addr. -- You need to change that function to change the memory map, independent of any -- additional address decoding you may do out of the FPGA (e.g. if you have more -- than one chip on any data bus) or out of the MCU module (e.g. when you add -- new IO registers). -- Please see the module c2sb_demo and mips_mcu for examples of memory decoding. -------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_arith.all; use ieee.std_logic_unsigned.all; package mips_pkg is ---- Basic types --------------------------------------------------------------- subtype t_word is std_logic_vector(31 downto 0); ---- System configuration constants -------------------------------------------- -- True to use standard-ish MIPS-1 memory map, false to use Plasma's -- (see implementation of function decode_addr below). constant USE_MIPS1_ADDR_MAP : boolean := true; -- Reset vector address minus 4 (0xfffffffc for Plasma, 0xbfbffffc for mips1) constant RESET_VECTOR_M4 : t_word := X"bfbffffc"; -- Trap vector address (0x0000003c for Plasma, 0xbfc00180 for mips1) constant TRAP_VECTOR : t_word := X"bfc00180"; ---- Address decoding ---------------------------------------------------------- -- Note: it is the cache module that does all internal address decoding -------- -- This is the slice of the address that will be used to decode memory areas subtype t_addr_decode is std_logic_vector(31 downto 24); -- Part of the memory area attribute: the type of memory determines how the -- cache module handles each block subtype t_memory_type is std_logic_vector(7 downto 5); -- These are all the types the cache knows about constant MT_BRAM : t_memory_type := "000"; constant MT_IO_SYNC : t_memory_type := "001"; constant MT_SRAM_16B : t_memory_type := "010"; constant MT_SRAM_8B : t_memory_type := "011"; constant MT_DDR_16B : t_memory_type := "100"; constant MT_UNMAPPED : t_memory_type := "111"; -- Wait state counter -- we're supporting static memory from 10 to >100 ns subtype t_wait_state_count is std_logic_vector(2 downto 0); -- 'Attributes' of some memory block -- used when decoding memory addresses type t_range_attr is record mem_type : t_memory_type; writeable : std_logic; cacheable : std_logic; wait_states : t_wait_state_count; end record t_range_attr; ---- More basic types and constants -------------------------------------------- subtype t_addr is std_logic_vector(31 downto 0); subtype t_dword is std_logic_vector(63 downto 0); subtype t_regnum is std_logic_vector(4 downto 0); type t_rbank is array(0 to 31) of t_word; subtype t_pc is std_logic_vector(31 downto 2); -- This is used as a textual shortcut only constant ZERO : t_word := (others => '0'); -- control word for ALU type t_alu_control is record logic_sel : std_logic_vector(1 downto 0); shift_sel : std_logic_vector(1 downto 0); shift_amount : std_logic_vector(4 downto 0); neg_sel : std_logic_vector(1 downto 0); use_arith : std_logic; use_logic : std_logic_vector(1 downto 0); cy_in : std_logic; use_slt : std_logic; arith_unsigned : std_logic; end record t_alu_control; -- Flags coming from the ALU type t_alu_flags is record inp1_lt_zero : std_logic; inp1_eq_zero : std_logic; inp1_lt_inp2 : std_logic; inp1_eq_inp2 : std_logic; end record t_alu_flags; -- 32-cycle mul/div module control. Bits 4-3 & 1-0 of IR. subtype t_mult_function is std_logic_vector(3 downto 0); constant MULT_NOTHING : t_mult_function := "0000"; constant MULT_READ_LO : t_mult_function := "1010"; -- 18 constant MULT_READ_HI : t_mult_function := "1000"; -- 16 constant MULT_WRITE_LO : t_mult_function := "1011"; -- 19 constant MULT_WRITE_HI : t_mult_function := "1001"; -- 17 constant MULT_MULT : t_mult_function := "1101"; -- 25 constant MULT_SIGNED_MULT : t_mult_function := "1100"; -- 24 constant MULT_DIVIDE : t_mult_function := "1111"; -- 26 constant MULT_SIGNED_DIVIDE : t_mult_function := "1110"; -- 27 -- Computes ceil(log2(A)), e.g. address width of memory block -- CAN BE USED IN SYNTHESIZABLE CODE as long as called with constant arguments function log2(A : natural) return natural; -- Decodes a memory address, gives the type of memory -- CAN BE USED IN SYNTHESIZABLE CODE, argument does not need to be constant function decode_addr(addr : t_addr_decode) return t_range_attr; end package; package body mips_pkg is function log2(A : natural) return natural is begin for I in 1 to 30 loop -- Works for up to 32 bit integers if(2**I > A) then return(I-1); end if; end loop; return(30); end function log2; -- Address decoding for Plasma-like system function decode_addr_plasma(addr : t_addr_decode) return t_range_attr is begin case addr(31 downto 27) is when "00000" => return (MT_BRAM ,'0','0',"000"); -- useg when "10000" => return (MT_SRAM_16B ,'1','1',"000"); -- kseg0 when "00100" => return (MT_IO_SYNC ,'1','0',"000"); -- kseg1 i/o when others => return (MT_UNMAPPED ,'0','0',"000"); -- stray end case; end function decode_addr_plasma; -- Address decoding for MIPS-I-like system as implemented in target hardware function decode_addr_mips1(addr : t_addr_decode) return t_range_attr is begin case addr(31 downto 27) is when "00000" => return (MT_SRAM_16B ,'1','1',"000"); -- useg when "10000" => return (MT_SRAM_16B ,'1','1',"000"); -- kseg0 --when "10100" => return (MT_IO_SYNC ,'1','0',"000"); -- kseg1 i/o when "00100" => return (MT_IO_SYNC ,'1','0',"000"); -- kseg1 i/o when "10110" => return (MT_SRAM_8B ,'0','0',"011"); -- kseg1 flash when "10111" => return (MT_BRAM ,'0','0',"000"); -- kseg1 boot rom when others => return (MT_UNMAPPED ,'0','0',"000"); -- stray end case; end function decode_addr_mips1; function decode_addr(addr : t_addr_decode) return t_range_attr is begin if USE_MIPS1_ADDR_MAP then return decode_addr_mips1(addr); else return decode_addr_plasma(addr); end if; end function decode_addr; end package body;
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