Subversion Repositories open8_urisc

-- VHDL Units :  Open8_cfg
-- Description:  Contains an example Open8_cfg file
--
-- Revision History
-- Author          Date     Change
------------------ -------- ---------------------------------------------------
-- Seth Henry      10/21/20 Design Start
 
library ieee;
  use ieee.std_logic_1164.all;
  use ieee.std_logic_unsigned.all;
  use ieee.std_logic_arith.all;
 
library work;
  use work.open8_pkg.all;
 
package open8_cfg is
 
  -- Internal Clock Frequency
  constant Clock_Frequency          : real      := 120000000.0;
 
    -- Open8 CPU Options
  constant Allow_Stack_Address_Move : boolean   := TRUE;
  constant Stack_Xfer_Flag          : integer   := PSR_GP4;
  constant Enable_Auto_Increment    : boolean   := TRUE;
  constant BRK_Implements_WAI       : boolean   := TRUE;
  constant Enable_NMI               : boolean   := TRUE;
  constant Sequential_Interrupts    : boolean   := TRUE;
  constant RTI_Ignores_GP_Flags     : boolean   := TRUE;
  constant Supervisor_Mode          : boolean   := TRUE;
  constant Unsigned_Index_Offsets   : boolean   := TRUE;
  constant Default_Int_Mask         : DATA_TYPE := x"00";
 
  -- System Memory Map
  constant RAM_Address              : ADDRESS_TYPE := x"0000";  -- System RAM
  constant WPR_Address              : ADDRESS_TYPE := x"1000";  -- Write Protect Mask
  constant WQL_Address              : ADDRESS_TYPE := x"1100";  -- Write Qual Register
  constant INT_Address              : ADDRESS_TYPE := x"1200";  -- Interrupt Manager
  constant ROM_Address              : ADDRESS_TYPE := x"8000";  -- Application ROM
  constant ISR_Start_Addr           : ADDRESS_TYPE := x"FFF0";  -- ISR vector table
 
  -- RAM size is used to calculate the initial stack pointer, which is set at
  --  the top of the RAM region.
  constant RAM_Size                 : integer   := 4096;
 
  constant RAM_Write_Protect        : boolean   := TRUE;
 
  -- CPU Interrupt assignments - Note that interrupt 0 is the NMI (non-maskable)
  --  also, because these are handled by the CPU, they are in priority order
  --  from 0 (highest) to 7 (lowest).
  constant CPU_INT_RAM              : integer range 0 to OPEN8_DATA_WIDTH - 1 := 0;
  constant CPU_INT_PIT              : integer range 0 to OPEN8_DATA_WIDTH - 1 := 1;
  constant CPU_INT_EXT              : integer range 0 to OPEN8_DATA_WIDTH - 1 := 2;
 
  -- I/O Interrupt assignments (Not technically required, as software will overwrite
  --  this during initialization)
  constant Default_IO_Int_Mask      : ADDRESS_TYPE := x"0000";
 
  -- Set this to the number of readable modules in the design, as it sets the
  --  number of ports on the read aggregator function.
  constant NUM_READ_BUSES           : integer := 4;
 
  -- Read Data Bus aggregator and bus assignments.
  --  Note that the ordering isn't important, only that each device has a
  --   unique number less than NUM_READ_BUSES.
  constant RDB_RAM                  : integer range 0 to NUM_READ_BUSES - 1   :=  0;
  constant RDB_WQL                  : integer range 0 to NUM_READ_BUSES - 1   :=  1;
  constant RDB_INT                  : integer range 0 to NUM_READ_BUSES - 1   :=  2;
  constant RDB_ROM                  : integer range 0 to NUM_READ_BUSES - 1   :=  3;
 
  -- System configuration calculations - no adjustable parameters below this point
  type OPEN8_BUS_ARRAY is array(0 to NUM_READ_BUSES - 1) of DATA_TYPE;
 
  constant INIT_READ_BUS            : OPEN8_BUS_ARRAY := (others => OPEN8_NULLBUS);
 
  function merge_buses (x : in OPEN8_BUS_ARRAY) return DATA_TYPE;
 
  -- Compute the stack start address based on the RAM size
  constant RAM_Vector_Size          : integer := ceil_log2(RAM_Size - 1);
  constant RAM_End_Addr             : std_logic_vector(RAM_Vector_Size - 1 downto 0)
                                     := (others => '1');
 
  constant Stack_Start_Addr         : ADDRESS_TYPE := RAM_Address + RAM_End_Addr;
 
end package;
 
package body open8_cfg is
 
  function merge_buses (x : in OPEN8_BUS_ARRAY) return DATA_TYPE is
    variable i               : integer   := 0;
    variable retval          : DATA_TYPE := x"00";
  begin
    retval                   := x"00";
    for i in 0 to NUM_READ_BUSES - 1 loop
      retval                 := retval or x(i);
    end loop;
    return retval;
  end function;
 
end package body;