URL https://opencores.org/ocsvn/hf-risc/hf-risc/trunk

Subversion Repositories hf-risc

[/] [hf-risc/] [trunk/] [hf-riscv/] [core_rv32i/] [datapath.vhd] - Blame information for rev 13

Go to most recent revision | Details | Compare with Previous | View Log


library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
 
entity datapath is
        port (  clock:          in std_logic;
                reset:          in std_logic;
 
                stall:          in std_logic;
                busy:           in std_logic;
 
                irq_vector:     in std_logic_vector(31 downto 0);
                irq:            in std_logic;
                irq_ack:        out std_logic;
                exception:      out std_logic;
 
                inst_addr:      out std_logic_vector(31 downto 0);
                inst_in:        in std_logic_vector(31 downto 0);
 
                data_addr:      out std_logic_vector(31 downto 0);
                data_in:        in std_logic_vector(31 downto 0);
                data_out:       out std_logic_vector(31 downto 0);
                data_w:         out std_logic_vector(3 downto 0);
                data_access:    out std_logic
        );
end datapath;
 
architecture arch_datapath of datapath is
-- datapath signals
        signal inst_in_s, data_in_s, pc, pc_last, pc_last2, pc_plus4, pc_next, result, branch, ext32b, ext32h, alu_src1, alu_src2: std_logic_vector(31 downto 0);
        signal ext32: std_logic_vector(31 downto 12);
        signal opcode, funct7: std_logic_vector(6 downto 0);
        signal funct3: std_logic_vector(2 downto 0);
        signal read_reg1, read_reg2, write_reg, rs1, rs2, rd: std_logic_vector(4 downto 0);
        signal write_data, read_data1, read_data2: std_logic_vector(31 downto 0);
        signal imm_i, imm_s, imm_sb, imm_uj, branch_src1, branch_src2: std_logic_vector(31 downto 0);
        signal imm_u: std_logic_vector(31 downto 12);
        signal wreg, zero, less_than, branch_taken, branch_taken_dly, jump_taken, jump_taken_dly, stall_reg: std_logic;
        signal irq_ack_s, irq_ack_s_dly, bds: std_logic;
 
-- control signals
        signal reg_write_ctl, alu_src1_ctl, sig_read_ctl, reg_to_mem, mem_to_reg, except: std_logic;
        signal jump_ctl, mem_write_ctl, mem_read_ctl: std_logic_vector(1 downto 0);
        signal alu_src2_ctl, branch_ctl: std_logic_vector(2 downto 0);
        signal alu_op_ctl: std_logic_vector(3 downto 0);
 
        signal rs1_r, rs2_r, rd_r: std_logic_vector(4 downto 0);
        signal imm_i_r, imm_s_r, imm_sb_r, imm_uj_r: std_logic_vector(31 downto 0);
        signal imm_u_r: std_logic_vector(31 downto 12);
        signal reg_write_ctl_r, alu_src1_ctl_r, sig_read_ctl_r, reg_to_mem_r, mem_to_reg_r, mem_to_reg_r_dly: std_logic;
        signal jump_ctl_r, mem_write_ctl_r, mem_read_ctl_r: std_logic_vector(1 downto 0);
        signal alu_src2_ctl_r, branch_ctl_r: std_logic_vector(2 downto 0);
        signal alu_op_ctl_r: std_logic_vector(3 downto 0);
begin
 
--
-- FETCH STAGE
--
-- 1st stage, instruction memory access, PC update, interrupt acknowledge logic
 
        -- program counter logic
        process(clock, reset, reg_to_mem_r, mem_to_reg_r, busy, stall)
        begin
                if reset = '1' then
                        pc <= (others => '0');
                        pc_last <= (others => '0');
                        pc_last2 <= (others => '0');
                elsif clock'event and clock = '1' then
                        if stall = '0' then
                                if busy = '0' then
                                        pc <= pc_next;
                                        pc_last <= pc;
                                        pc_last2 <= pc_last;
                                else
                                        if (reg_to_mem_r = '1' or mem_to_reg_r = '1' or except = '1') and branch_taken_dly = '0' and jump_taken_dly = '0' then
                                                pc <= pc_last;
                                        end if;
                                end if;
                        end if;
                end if;
        end process;
 
        pc_plus4 <=     pc + 4;
 
        pc_next <=      irq_vector when (irq = '1' and irq_ack_s = '1') or except = '1' else
                        branch when branch_taken = '1' or jump_taken = '1' else
                        pc_plus4;
 
        -- interrupt acknowledge logic
        irq_ack_s <= '1' when irq = '1' and
                bds = '0' and branch_taken = '0' and jump_taken = '0' and
                reg_to_mem_r = '0' and mem_to_reg_r = '0' else '0';
 
        irq_ack <= irq_ack_s_dly;
 
        exception <= '1' when except = '1' else '0';
 
        process(clock, reset, irq, irq_ack_s, mem_to_reg_r, busy, stall)
        begin
                if reset = '1' then
                        irq_ack_s_dly <= '0';
                        bds <= '0';
                        branch_taken_dly <= '0';
                        jump_taken_dly <= '0';
                        mem_to_reg_r_dly <= '0';
                        stall_reg <= '0';
                elsif clock'event and clock = '1' then
                        stall_reg <= stall;
                        if stall = '0' then
                                mem_to_reg_r_dly <= mem_to_reg_r;
                                if busy = '0' then
                                        irq_ack_s_dly <= irq_ack_s;
                                        if branch_taken = '1' or jump_taken = '1' then
                                                bds <= '1';
                                        else
                                                bds <= '0';
                                        end if;
                                        branch_taken_dly <= branch_taken or except;
                                        jump_taken_dly <= jump_taken;
                                end if;
                        end if;
                end if;
        end process;
 
--
-- DECODE STAGE
--
-- 2nd stage, instruction decode, control unit operation, pipeline bubble insertion logic on load/store and branches
 
        -- instruction decode
        inst_in_s <= inst_in(7 downto 0) & inst_in(15 downto 8) & inst_in(23 downto 16) & inst_in(31 downto 24);
 
        opcode <= inst_in_s(6 downto 0);
        funct3 <= inst_in_s(14 downto 12);
        funct7 <= inst_in_s(31 downto 25);
        rd <= inst_in_s(11 downto 7);
        rs1 <= inst_in_s(19 downto 15);
        rs2 <= inst_in_s(24 downto 20);
        imm_i <= ext32(31 downto 12) & inst_in_s(31 downto 20);
        imm_s <= ext32(31 downto 12) & inst_in_s(31 downto 25) & inst_in_s(11 downto 7);
        imm_sb <= ext32(31 downto 13) & inst_in_s(31) & inst_in_s(7) & inst_in_s(30 downto 25) & inst_in_s(11 downto 8) & '0';
        imm_u <= inst_in_s(31 downto 12);
        imm_uj <= ext32(31 downto 21) & inst_in_s(31) & inst_in_s(19 downto 12) & inst_in_s(20) & inst_in_s(30 downto 21) & '0';
        ext32 <= (others => '1') when inst_in_s(31) = '1' else (others => '0');
 
        -- control unit
        control_hellfire: entity work.control
        port map(       opcode => opcode,
                        funct3 => funct3,
                        funct7 => funct7,
                        reg_write => reg_write_ctl,
                        alu_src1 => alu_src1_ctl,
                        alu_src2 => alu_src2_ctl,
                        alu_op => alu_op_ctl,
                        jump => jump_ctl,
                        branch => branch_ctl,
                        mem_write => mem_write_ctl,
                        mem_read => mem_read_ctl,
                        sig_read => sig_read_ctl
        );
 
        reg_to_mem <= '1' when mem_write_ctl /= "00" else '0';
        mem_to_reg <= '1' when mem_read_ctl /= "00" else '0';
 
        process(clock, reset, irq_ack_s, bds, busy, stall)
        begin
                if reset = '1' then
                        rd_r <= (others => '0');
                        rs1_r <= (others => '0');
                        rs2_r <= (others => '0');
                        imm_i_r <= (others => '0');
                        imm_s_r <= (others => '0');
                        imm_sb_r <= (others => '0');
                        imm_u_r <= (others => '0');
                        imm_uj_r <= (others => '0');
                        reg_write_ctl_r <= '0';
                        alu_src1_ctl_r <= '0';
                        alu_src2_ctl_r <= (others => '0');
                        alu_op_ctl_r <= (others => '0');
                        jump_ctl_r <= (others => '0');
                        branch_ctl_r <= (others => '0');
                        mem_write_ctl_r <= (others => '0');
                        mem_read_ctl_r <= (others => '0');
                        sig_read_ctl_r <= '0';
                        reg_to_mem_r <= '0';
                        mem_to_reg_r <= '0';
                elsif clock'event and clock = '1' then
                        if stall = '0' then
                                if irq_ack_s = '1' then
                                        rd_r <= (others => '0');
                                        rs1_r <= (others => '0');
                                        rs2_r <= (others => '0');
                                        imm_i_r <= (others => '0');
                                        imm_s_r <= (others => '0');
                                        imm_sb_r <= (others => '0');
                                        imm_u_r <= (others => '0');
                                        imm_uj_r <= (others => '0');
                                        reg_write_ctl_r <= '0';
                                        alu_src1_ctl_r <= '0';
                                        alu_src2_ctl_r <= (others => '0');
                                        alu_op_ctl_r <= (others => '0');
                                        jump_ctl_r <= (others => '0');
                                        branch_ctl_r <= (others => '0');
                                        mem_write_ctl_r <= (others => '0');
                                        mem_read_ctl_r <= (others => '0');
                                        sig_read_ctl_r <= '0';
                                        reg_to_mem_r <= '0';
                                        mem_to_reg_r <= '0';
                                else
                                        if busy = '0' then
                                                if (reg_to_mem_r = '1' or mem_to_reg_r = '1' or except = '1' or branch_taken = '1' or jump_taken = '1' or branch_taken_dly = '1' or jump_taken_dly = '1') then
                                                        rd_r <= (others => '0');
                                                        rs1_r <= (others => '0');
                                                        rs2_r <= (others => '0');
                                                        imm_i_r <= (others => '0');
                                                        imm_s_r <= (others => '0');
                                                        imm_sb_r <= (others => '0');
                                                        imm_u_r <= (others => '0');
                                                        imm_uj_r <= (others => '0');
                                                        reg_write_ctl_r <= '0';
                                                        alu_src1_ctl_r <= '0';
                                                        alu_src2_ctl_r <= (others => '0');
                                                        alu_op_ctl_r <= (others => '0');
                                                        jump_ctl_r <= (others => '0');
                                                        branch_ctl_r <= (others => '0');
                                                        mem_write_ctl_r <= (others => '0');
                                                        mem_read_ctl_r <= (others => '0');
                                                        sig_read_ctl_r <= '0';
                                                        reg_to_mem_r <= '0';
                                                        mem_to_reg_r <= '0';
                                                else
                                                        rd_r <= rd;
                                                        rs1_r <= rs1;
                                                        rs2_r <= rs2;
                                                        imm_i_r <= imm_i;
                                                        imm_s_r <= imm_s;
                                                        imm_sb_r <= imm_sb;
                                                        imm_u_r <= imm_u;
                                                        imm_uj_r <= imm_uj;
                                                        reg_write_ctl_r <= reg_write_ctl;
                                                        alu_src1_ctl_r <= alu_src1_ctl;
                                                        alu_src2_ctl_r <= alu_src2_ctl;
                                                        alu_op_ctl_r <= alu_op_ctl;
                                                        jump_ctl_r <= jump_ctl;
                                                        branch_ctl_r <= branch_ctl;
                                                        mem_write_ctl_r <= mem_write_ctl;
                                                        mem_read_ctl_r <= mem_read_ctl;
                                                        sig_read_ctl_r <= sig_read_ctl;
                                                        reg_to_mem_r <= reg_to_mem;
                                                        mem_to_reg_r <= mem_to_reg;
                                                end if;
                                        end if;
                                end if;
                        end if;
                end if;
        end process;
 
--
-- EXECUTE STAGE
--
 
-- 3rd stage (a) register file access (read)
        -- the register file
        register_bank: entity work.reg_bank
        port map(       clock => clock,
                        read_reg1 => read_reg1,
                        read_reg2 => read_reg2,
                        write_reg => write_reg,
                        wreg => wreg,
                        write_data => write_data,
                        read_data1 => read_data1,
                        read_data2 => read_data2
        );
 
        -- register file read/write selection and write enable
        read_reg1 <= rs1_r;
        read_reg2 <= rs2_r;
        write_reg <= rd_r;
        wreg <= (reg_write_ctl_r or mem_to_reg_r_dly) and not busy and not stall_reg;
 
-- 3rd stage (b) ALU operation
        alu: entity work.alu
        port map(       op1 => alu_src1,
                        op2 => alu_src2,
                        alu_op => alu_op_ctl_r,
                        result => result,
                        zero => zero,
                        less_than => less_than
        );
 
        alu_src1 <= read_data1 when alu_src1_ctl_r = '0' else pc_last2;
        alu_src2 <=     imm_u_r & x"000" when alu_src2_ctl_r = "000" else
                        imm_i_r when alu_src2_ctl_r = "001" else
                        imm_s_r when alu_src2_ctl_r = "010" else
                        pc when alu_src2_ctl_r = "011" else
                        x"000000" & "000" & rs2_r when alu_src2_ctl_r = "100" else
                        read_data2;
 
        branch_src1 <= read_data1 when jump_ctl_r = "11" else pc_last2;
        branch_src2 <= imm_uj_r when jump_ctl_r = "10" else
                        imm_i_r when jump_ctl_r = "11" else imm_sb_r;
 
        branch <= branch_src1 + branch_src2;
 
        branch_taken <= '1' when (zero = '1' and branch_ctl_r = "001") or                                               -- BEQ
                                (zero = '0' and branch_ctl_r = "010") or                                         -- BNE
                                (less_than = '1' and branch_ctl_r = "011") or                                           -- BLT
                                (less_than = '0' and branch_ctl_r = "100") or                                            -- BGE
                                (less_than = '1' and branch_ctl_r = "101") or                                           -- BLTU
                                (less_than = '0' and branch_ctl_r = "110")                                               -- BGEU
                                else '0';
        except <= '1' when branch_ctl_r = "111" else '0';
        jump_taken <= '1' when jump_ctl_r /= "00" else '0';
 
        inst_addr <= pc;
        data_addr <= result; --result(31 downto 2) & "00";
        data_access <= '1' when reg_to_mem_r = '1' or mem_to_reg_r = '1' else '0';
 
 
-- 3rd stage (c) data memory / write back operation, register file access (write)
        -- memory access, store operations
        process(mem_write_ctl_r, result, read_data2)
        begin
                case mem_write_ctl_r is
                        when "11" =>                    -- store word
                                data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(23 downto 16) & read_data2(31 downto 24);
                                data_w <= "1111";
                        when "01" =>                    -- store byte
                                data_out <= read_data2(7 downto 0) & read_data2(7 downto 0) & read_data2(7 downto 0) & read_data2(7 downto 0);
                                case result(1 downto 0) is
                                        when "11" => data_w <= "0001";
                                        when "10" => data_w <= "0010";
                                        when "01" => data_w <= "0100";
                                        when others => data_w <= "1000";
                                end case;
                        when "10" =>                    -- store half word
                                data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(7 downto 0) & read_data2(15 downto 8);
                                case result(1) is
                                        when '1' => data_w <= "0011";
                                        when others => data_w <= "1100";
                                end case;
                        when others =>                  -- WTF??
                                data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(23 downto 16) & read_data2(31 downto 24);
                                data_w <= "0000";
                end case;
        end process;
 
        -- memory access, load operations
        process(mem_read_ctl_r, result, data_in)
        begin
                case mem_read_ctl_r is
                        when "01" =>                    -- load byte
                                case result(1 downto 0) is
                                        when "11" => data_in_s <= x"000000" & data_in(7 downto 0);
                                        when "10" => data_in_s <= x"000000" & data_in(15 downto 8);
                                        when "01" => data_in_s <= x"000000" & data_in(23 downto 16);
                                        when others => data_in_s <= x"000000" & data_in(31 downto 24);
 
                                end case;
                        when "10" =>                    -- load half word
                                case result(1) is
                                        when '1' => data_in_s <= x"0000" & data_in(7 downto 0) & data_in(15 downto 8);
                                        when others => data_in_s <= x"0000" & data_in(23 downto 16) & data_in(31 downto 24);
                                end case;
                        when others =>                  -- load word
                                data_in_s <= data_in(7 downto 0) & data_in(15 downto 8) & data_in(23 downto 16) & data_in(31 downto 24);
                end case;
        end process;
 
        -- write back
        ext32b <= x"000000" & data_in_s(7 downto 0) when (data_in_s(7) = '0' or sig_read_ctl_r = '0') else x"ffffff" & data_in_s(7 downto 0);
        ext32h <= x"0000" & data_in_s(15 downto 0) when (data_in_s(15) = '0' or sig_read_ctl_r = '0') else x"ffff" & data_in_s(15 downto 0);
 
        write_data <= data_in_s when mem_read_ctl_r = "11" else
                        ext32b when mem_read_ctl_r = "01" else
                        ext32h when mem_read_ctl_r = "10" else
                        pc_last when jump_taken = '1' else result;
 
end arch_datapath;
 

Browse

Tools

Subversion Repositories hf-risc

[/] [hf-risc/] [trunk/] [hf-riscv/] [core_rv32i/] [datapath.vhd] - Blame information for rev 13

Line No.	Rev	Author	Line
1	13	serginhofr	`library ieee;`
2			`use ieee.std_logic_1164.all;`
3			`use ieee.std_logic_unsigned.all;`
4			`use ieee.std_logic_arith.all;`
5
6			`entity datapath is`
7			`port ( clock: in std_logic;`
8			`reset: in std_logic;`
9
10			`stall: in std_logic;`
11			`busy: in std_logic;`
12
13			`irq_vector: in std_logic_vector(31 downto 0);`
14			`irq: in std_logic;`
15			`irq_ack: out std_logic;`
16			`exception: out std_logic;`
17
18			`inst_addr: out std_logic_vector(31 downto 0);`
19			`inst_in: in std_logic_vector(31 downto 0);`
20
21			`data_addr: out std_logic_vector(31 downto 0);`
22			`data_in: in std_logic_vector(31 downto 0);`
23			`data_out: out std_logic_vector(31 downto 0);`
24			`data_w: out std_logic_vector(3 downto 0);`
25			`data_access: out std_logic`
26			`);`
27			`end datapath;`
28
29			`architecture arch_datapath of datapath is`
30			`-- datapath signals`
31			`signal inst_in_s, data_in_s, pc, pc_last, pc_last2, pc_plus4, pc_next, result, branch, ext32b, ext32h, alu_src1, alu_src2: std_logic_vector(31 downto 0);`
32			`signal ext32: std_logic_vector(31 downto 12);`
33			`signal opcode, funct7: std_logic_vector(6 downto 0);`
34			`signal funct3: std_logic_vector(2 downto 0);`
35			`signal read_reg1, read_reg2, write_reg, rs1, rs2, rd: std_logic_vector(4 downto 0);`
36			`signal write_data, read_data1, read_data2: std_logic_vector(31 downto 0);`
37			`signal imm_i, imm_s, imm_sb, imm_uj, branch_src1, branch_src2: std_logic_vector(31 downto 0);`
38			`signal imm_u: std_logic_vector(31 downto 12);`
39			`signal wreg, zero, less_than, branch_taken, branch_taken_dly, jump_taken, jump_taken_dly, stall_reg: std_logic;`
40			`signal irq_ack_s, irq_ack_s_dly, bds: std_logic;`
41
42			`-- control signals`
43			`signal reg_write_ctl, alu_src1_ctl, sig_read_ctl, reg_to_mem, mem_to_reg, except: std_logic;`
44			`signal jump_ctl, mem_write_ctl, mem_read_ctl: std_logic_vector(1 downto 0);`
45			`signal alu_src2_ctl, branch_ctl: std_logic_vector(2 downto 0);`
46			`signal alu_op_ctl: std_logic_vector(3 downto 0);`
47
48			`signal rs1_r, rs2_r, rd_r: std_logic_vector(4 downto 0);`
49			`signal imm_i_r, imm_s_r, imm_sb_r, imm_uj_r: std_logic_vector(31 downto 0);`
50			`signal imm_u_r: std_logic_vector(31 downto 12);`
51			`signal reg_write_ctl_r, alu_src1_ctl_r, sig_read_ctl_r, reg_to_mem_r, mem_to_reg_r, mem_to_reg_r_dly: std_logic;`
52			`signal jump_ctl_r, mem_write_ctl_r, mem_read_ctl_r: std_logic_vector(1 downto 0);`
53			`signal alu_src2_ctl_r, branch_ctl_r: std_logic_vector(2 downto 0);`
54			`signal alu_op_ctl_r: std_logic_vector(3 downto 0);`
55			`begin`
56
57			`--`
58			`-- FETCH STAGE`
59			`--`
60			`-- 1st stage, instruction memory access, PC update, interrupt acknowledge logic`
61
62			`-- program counter logic`
63			`process(clock, reset, reg_to_mem_r, mem_to_reg_r, busy, stall)`
64			`begin`
65			`if reset = '1' then`
66			`pc <= (others => '0');`
67			`pc_last <= (others => '0');`
68			`pc_last2 <= (others => '0');`
69			`elsif clock'event and clock = '1' then`
70			`if stall = '0' then`
71			`if busy = '0' then`
72			`pc <= pc_next;`
73			`pc_last <= pc;`
74			`pc_last2 <= pc_last;`
75			`else`
76			`if (reg_to_mem_r = '1' or mem_to_reg_r = '1' or except = '1') and branch_taken_dly = '0' and jump_taken_dly = '0' then`
77			`pc <= pc_last;`
78			`end if;`
79			`end if;`
80			`end if;`
81			`end if;`
82			`end process;`
83
84			`pc_plus4 <= pc + 4;`
85
86			`pc_next <= irq_vector when (irq = '1' and irq_ack_s = '1') or except = '1' else`
87			`branch when branch_taken = '1' or jump_taken = '1' else`
88			`pc_plus4;`
89
90			`-- interrupt acknowledge logic`
91			`irq_ack_s <= '1' when irq = '1' and`
92			`bds = '0' and branch_taken = '0' and jump_taken = '0' and`
93			`reg_to_mem_r = '0' and mem_to_reg_r = '0' else '0';`
94
95			`irq_ack <= irq_ack_s_dly;`
96
97			`exception <= '1' when except = '1' else '0';`
98
99			`process(clock, reset, irq, irq_ack_s, mem_to_reg_r, busy, stall)`
100			`begin`
101			`if reset = '1' then`
102			`irq_ack_s_dly <= '0';`
103			`bds <= '0';`
104			`branch_taken_dly <= '0';`
105			`jump_taken_dly <= '0';`
106			`mem_to_reg_r_dly <= '0';`
107			`stall_reg <= '0';`
108			`elsif clock'event and clock = '1' then`
109			`stall_reg <= stall;`
110			`if stall = '0' then`
111			`mem_to_reg_r_dly <= mem_to_reg_r;`
112			`if busy = '0' then`
113			`irq_ack_s_dly <= irq_ack_s;`
114			`if branch_taken = '1' or jump_taken = '1' then`
115			`bds <= '1';`
116			`else`
117			`bds <= '0';`
118			`end if;`
119			`branch_taken_dly <= branch_taken or except;`
120			`jump_taken_dly <= jump_taken;`
121			`end if;`
122			`end if;`
123			`end if;`
124			`end process;`
125
126			`--`
127			`-- DECODE STAGE`
128			`--`
129			`-- 2nd stage, instruction decode, control unit operation, pipeline bubble insertion logic on load/store and branches`
130
131			`-- instruction decode`
132			`inst_in_s <= inst_in(7 downto 0) & inst_in(15 downto 8) & inst_in(23 downto 16) & inst_in(31 downto 24);`
133
134			`opcode <= inst_in_s(6 downto 0);`
135			`funct3 <= inst_in_s(14 downto 12);`
136			`funct7 <= inst_in_s(31 downto 25);`
137			`rd <= inst_in_s(11 downto 7);`
138			`rs1 <= inst_in_s(19 downto 15);`
139			`rs2 <= inst_in_s(24 downto 20);`
140			`imm_i <= ext32(31 downto 12) & inst_in_s(31 downto 20);`
141			`imm_s <= ext32(31 downto 12) & inst_in_s(31 downto 25) & inst_in_s(11 downto 7);`
142			`imm_sb <= ext32(31 downto 13) & inst_in_s(31) & inst_in_s(7) & inst_in_s(30 downto 25) & inst_in_s(11 downto 8) & '0';`
143			`imm_u <= inst_in_s(31 downto 12);`
144			`imm_uj <= ext32(31 downto 21) & inst_in_s(31) & inst_in_s(19 downto 12) & inst_in_s(20) & inst_in_s(30 downto 21) & '0';`
145			`ext32 <= (others => '1') when inst_in_s(31) = '1' else (others => '0');`
146
147			`-- control unit`
148			`control_hellfire: entity work.control`
149			`port map( opcode => opcode,`
150			`funct3 => funct3,`
151			`funct7 => funct7,`
152			`reg_write => reg_write_ctl,`
153			`alu_src1 => alu_src1_ctl,`
154			`alu_src2 => alu_src2_ctl,`
155			`alu_op => alu_op_ctl,`
156			`jump => jump_ctl,`
157			`branch => branch_ctl,`
158			`mem_write => mem_write_ctl,`
159			`mem_read => mem_read_ctl,`
160			`sig_read => sig_read_ctl`
161			`);`
162
163			`reg_to_mem <= '1' when mem_write_ctl /= "00" else '0';`
164			`mem_to_reg <= '1' when mem_read_ctl /= "00" else '0';`
165
166			`process(clock, reset, irq_ack_s, bds, busy, stall)`
167			`begin`
168			`if reset = '1' then`
169			`rd_r <= (others => '0');`
170			`rs1_r <= (others => '0');`
171			`rs2_r <= (others => '0');`
172			`imm_i_r <= (others => '0');`
173			`imm_s_r <= (others => '0');`
174			`imm_sb_r <= (others => '0');`
175			`imm_u_r <= (others => '0');`
176			`imm_uj_r <= (others => '0');`
177			`reg_write_ctl_r <= '0';`
178			`alu_src1_ctl_r <= '0';`
179			`alu_src2_ctl_r <= (others => '0');`
180			`alu_op_ctl_r <= (others => '0');`
181			`jump_ctl_r <= (others => '0');`
182			`branch_ctl_r <= (others => '0');`
183			`mem_write_ctl_r <= (others => '0');`
184			`mem_read_ctl_r <= (others => '0');`
185			`sig_read_ctl_r <= '0';`
186			`reg_to_mem_r <= '0';`
187			`mem_to_reg_r <= '0';`
188			`elsif clock'event and clock = '1' then`
189			`if stall = '0' then`
190			`if irq_ack_s = '1' then`
191			`rd_r <= (others => '0');`
192			`rs1_r <= (others => '0');`
193			`rs2_r <= (others => '0');`
194			`imm_i_r <= (others => '0');`
195			`imm_s_r <= (others => '0');`
196			`imm_sb_r <= (others => '0');`
197			`imm_u_r <= (others => '0');`
198			`imm_uj_r <= (others => '0');`
199			`reg_write_ctl_r <= '0';`
200			`alu_src1_ctl_r <= '0';`
201			`alu_src2_ctl_r <= (others => '0');`
202			`alu_op_ctl_r <= (others => '0');`
203			`jump_ctl_r <= (others => '0');`
204			`branch_ctl_r <= (others => '0');`
205			`mem_write_ctl_r <= (others => '0');`
206			`mem_read_ctl_r <= (others => '0');`
207			`sig_read_ctl_r <= '0';`
208			`reg_to_mem_r <= '0';`
209			`mem_to_reg_r <= '0';`
210			`else`
211			`if busy = '0' then`
212			`if (reg_to_mem_r = '1' or mem_to_reg_r = '1' or except = '1' or branch_taken = '1' or jump_taken = '1' or branch_taken_dly = '1' or jump_taken_dly = '1') then`
213			`rd_r <= (others => '0');`
214			`rs1_r <= (others => '0');`
215			`rs2_r <= (others => '0');`
216			`imm_i_r <= (others => '0');`
217			`imm_s_r <= (others => '0');`
218			`imm_sb_r <= (others => '0');`
219			`imm_u_r <= (others => '0');`
220			`imm_uj_r <= (others => '0');`
221			`reg_write_ctl_r <= '0';`
222			`alu_src1_ctl_r <= '0';`
223			`alu_src2_ctl_r <= (others => '0');`
224			`alu_op_ctl_r <= (others => '0');`
225			`jump_ctl_r <= (others => '0');`
226			`branch_ctl_r <= (others => '0');`
227			`mem_write_ctl_r <= (others => '0');`
228			`mem_read_ctl_r <= (others => '0');`
229			`sig_read_ctl_r <= '0';`
230			`reg_to_mem_r <= '0';`
231			`mem_to_reg_r <= '0';`
232			`else`
233			`rd_r <= rd;`
234			`rs1_r <= rs1;`
235			`rs2_r <= rs2;`
236			`imm_i_r <= imm_i;`
237			`imm_s_r <= imm_s;`
238			`imm_sb_r <= imm_sb;`
239			`imm_u_r <= imm_u;`
240			`imm_uj_r <= imm_uj;`
241			`reg_write_ctl_r <= reg_write_ctl;`
242			`alu_src1_ctl_r <= alu_src1_ctl;`
243			`alu_src2_ctl_r <= alu_src2_ctl;`
244			`alu_op_ctl_r <= alu_op_ctl;`
245			`jump_ctl_r <= jump_ctl;`
246			`branch_ctl_r <= branch_ctl;`
247			`mem_write_ctl_r <= mem_write_ctl;`
248			`mem_read_ctl_r <= mem_read_ctl;`
249			`sig_read_ctl_r <= sig_read_ctl;`
250			`reg_to_mem_r <= reg_to_mem;`
251			`mem_to_reg_r <= mem_to_reg;`
252			`end if;`
253			`end if;`
254			`end if;`
255			`end if;`
256			`end if;`
257			`end process;`
258
259			`--`
260			`-- EXECUTE STAGE`
261			`--`
262
263			`-- 3rd stage (a) register file access (read)`
264			`-- the register file`
265			`register_bank: entity work.reg_bank`
266			`port map( clock => clock,`
267			`read_reg1 => read_reg1,`
268			`read_reg2 => read_reg2,`
269			`write_reg => write_reg,`
270			`wreg => wreg,`
271			`write_data => write_data,`
272			`read_data1 => read_data1,`
273			`read_data2 => read_data2`
274			`);`
275
276			`-- register file read/write selection and write enable`
277			`read_reg1 <= rs1_r;`
278			`read_reg2 <= rs2_r;`
279			`write_reg <= rd_r;`
280			`wreg <= (reg_write_ctl_r or mem_to_reg_r_dly) and not busy and not stall_reg;`
281
282			`-- 3rd stage (b) ALU operation`
283			`alu: entity work.alu`
284			`port map( op1 => alu_src1,`
285			`op2 => alu_src2,`
286			`alu_op => alu_op_ctl_r,`
287			`result => result,`
288			`zero => zero,`
289			`less_than => less_than`
290			`);`
291
292			`alu_src1 <= read_data1 when alu_src1_ctl_r = '0' else pc_last2;`
293			`alu_src2 <= imm_u_r & x"000" when alu_src2_ctl_r = "000" else`
294			`imm_i_r when alu_src2_ctl_r = "001" else`
295			`imm_s_r when alu_src2_ctl_r = "010" else`
296			`pc when alu_src2_ctl_r = "011" else`
297			`x"000000" & "000" & rs2_r when alu_src2_ctl_r = "100" else`
298			`read_data2;`
299
300			`branch_src1 <= read_data1 when jump_ctl_r = "11" else pc_last2;`
301			`branch_src2 <= imm_uj_r when jump_ctl_r = "10" else`
302			`imm_i_r when jump_ctl_r = "11" else imm_sb_r;`
303
304			`branch <= branch_src1 + branch_src2;`
305
306			`branch_taken <= '1' when (zero = '1' and branch_ctl_r = "001") or -- BEQ`
307			`(zero = '0' and branch_ctl_r = "010") or -- BNE`
308			`(less_than = '1' and branch_ctl_r = "011") or -- BLT`
309			`(less_than = '0' and branch_ctl_r = "100") or -- BGE`
310			`(less_than = '1' and branch_ctl_r = "101") or -- BLTU`
311			`(less_than = '0' and branch_ctl_r = "110") -- BGEU`
312			`else '0';`
313			`except <= '1' when branch_ctl_r = "111" else '0';`
314			`jump_taken <= '1' when jump_ctl_r /= "00" else '0';`
315
316			`inst_addr <= pc;`
317			`data_addr <= result; --result(31 downto 2) & "00";`
318			`data_access <= '1' when reg_to_mem_r = '1' or mem_to_reg_r = '1' else '0';`
319
320
321			`-- 3rd stage (c) data memory / write back operation, register file access (write)`
322			`-- memory access, store operations`
323			`process(mem_write_ctl_r, result, read_data2)`
324			`begin`
325			`case mem_write_ctl_r is`
326			`when "11" => -- store word`
327			`data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(23 downto 16) & read_data2(31 downto 24);`
328			`data_w <= "1111";`
329			`when "01" => -- store byte`
330			`data_out <= read_data2(7 downto 0) & read_data2(7 downto 0) & read_data2(7 downto 0) & read_data2(7 downto 0);`
331			`case result(1 downto 0) is`
332			`when "11" => data_w <= "0001";`
333			`when "10" => data_w <= "0010";`
334			`when "01" => data_w <= "0100";`
335			`when others => data_w <= "1000";`
336			`end case;`
337			`when "10" => -- store half word`
338			`data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(7 downto 0) & read_data2(15 downto 8);`
339			`case result(1) is`
340			`when '1' => data_w <= "0011";`
341			`when others => data_w <= "1100";`
342			`end case;`
343			`when others => -- WTF??`
344			`data_out <= read_data2(7 downto 0) & read_data2(15 downto 8) & read_data2(23 downto 16) & read_data2(31 downto 24);`
345			`data_w <= "0000";`
346			`end case;`
347			`end process;`
348
349			`-- memory access, load operations`
350			`process(mem_read_ctl_r, result, data_in)`
351			`begin`
352			`case mem_read_ctl_r is`
353			`when "01" => -- load byte`
354			`case result(1 downto 0) is`
355			`when "11" => data_in_s <= x"000000" & data_in(7 downto 0);`
356			`when "10" => data_in_s <= x"000000" & data_in(15 downto 8);`
357			`when "01" => data_in_s <= x"000000" & data_in(23 downto 16);`
358			`when others => data_in_s <= x"000000" & data_in(31 downto 24);`
359
360			`end case;`
361			`when "10" => -- load half word`
362			`case result(1) is`
363			`when '1' => data_in_s <= x"0000" & data_in(7 downto 0) & data_in(15 downto 8);`
364			`when others => data_in_s <= x"0000" & data_in(23 downto 16) & data_in(31 downto 24);`
365			`end case;`
366			`when others => -- load word`
367			`data_in_s <= data_in(7 downto 0) & data_in(15 downto 8) & data_in(23 downto 16) & data_in(31 downto 24);`
368			`end case;`
369			`end process;`
370
371			`-- write back`
372			`ext32b <= x"000000" & data_in_s(7 downto 0) when (data_in_s(7) = '0' or sig_read_ctl_r = '0') else x"ffffff" & data_in_s(7 downto 0);`
373			`ext32h <= x"0000" & data_in_s(15 downto 0) when (data_in_s(15) = '0' or sig_read_ctl_r = '0') else x"ffff" & data_in_s(15 downto 0);`
374
375			`write_data <= data_in_s when mem_read_ctl_r = "11" else`
376			`ext32b when mem_read_ctl_r = "01" else`
377			`ext32h when mem_read_ctl_r = "10" else`
378			`pc_last when jump_taken = '1' else result;`
379
380			`end arch_datapath;`
381