befunge_processor/befunge_stack.vhd at master · mike7c2/befunge_processor · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
----------------------------------------------------------------------------------
-- Company:
-- Engineer:
--
-- Create Date:    22:21:54 12/01/2014
-- Design Name:
-- Module Name:    befunge_stack - Behavioral
-- Project Name:
-- Target Devices:
-- Tool versions:
-- Description:
--
-- Dependencies:
--
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
--
----------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use IEEE.numeric_std.all;

entity befunge_stack is
	generic(
	    stack_depth_pow  : integer := 4;
        word_size : integer := 8
	);

    port(
        clk          : in  std_logic;
        reset        : in  std_logic;
        stack_0_o    : out std_logic_vector(word_size-1 downto 0);
        stack_1_o    : out std_logic_vector(word_size-1 downto 0);
        stack_i      : in  std_logic_vector(word_size-1 downto 0);
        pop1         : in  std_logic;
        pop2         : in  std_logic;
        push         : in  std_logic;
        swap         : in  std_logic;
        en           : in  std_logic
    );
end befunge_stack;

architecture stack_v1 of befunge_stack is
   type stack_type is array ((2**stack_depth_pow)-1 downto 0) of std_logic_vector(word_size-1 downto 0);
   signal stack : stack_type;
   signal stack_ptr : Signed(stack_depth_pow-1 downto 0);
begin

    stack_0_o <= stack(to_integer(Unsigned(stack_ptr)));
    stack_1_o <= stack(to_integer(Unsigned(stack_ptr- 1)));

	process(reset,clk)
        variable ptr_incr : integer range -2 to 1;
	begin
        if(reset = '1') then
            --stack_0_o <= (others => '0');
            --stack_1_o <= (others => '0');
            stack <= (others => (others => '0'));
            stack_ptr <= (others => '0');
        else
            if rising_edge(clk) then
                ptr_incr := 0;
                if ( en = '1' ) then

                    if (pop1 = '1' or pop2 = '1' or push = '1') then
                        if ( pop1 = '1' ) then
                            ptr_incr := - 1;
                        elsif ( pop2 = '1' ) then
                            ptr_incr := - 2;
                        elsif ( push = '1' ) then
                            ptr_incr := 1;
                            stack(to_integer(Unsigned(stack_ptr + ptr_incr))) <= stack_i;
                        end if;


                    elsif (swap = '1' ) then
                        stack(to_integer(stack_ptr)) <= stack(to_integer(stack_ptr - 1));
                        stack(to_integer(stack_ptr - 1)) <= stack(to_integer(stack_ptr));

                        --stack_0_o <= stack(to_integer(stack_ptr + ptr_incr -1));
                        --stack_1_o <= stack(to_integer(stack_ptr + ptr_incr));
                    end if;

                    stack_ptr <= stack_ptr + ptr_incr;
                end if;
            end if;
		end if;
    end process;
end stack_v1;