Subversion Repositories hf-risc

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity hellfire_cpu_if is

        generic(

                address_width: integer := 14;

                memory_file : string := "code.txt";

                uart_support : string := "yes"

        );

        port (  clk_in:         in std_logic;

                reset_in:       in std_logic;

                int_in:         in std_logic;

                uart_read:      in std_logic;

                uart_write:     out std_logic;

                ram_address:    out std_logic_vector(31 downto 2);

                ram_data:       inout std_logic_vector(31 downto 0);

                ram_ce1_n:      out std_logic;

                ram_ub1_n:      out std_logic;

                ram_lb1_n:      out std_logic;

                ram_ce2_n:      out std_logic;

                ram_ub2_n:      out std_logic;

                ram_lb2_n:      out std_logic;

                ram_we_n:       out std_logic;

                ram_oe_n:       out std_logic

        );

end hellfire_cpu_if;

architecture interface of hellfire_cpu_if is

        signal clock, boot_enable, ram_enable_n, stall, stall_cpu, busy_cpu, irq_cpu, irq_ack_cpu, data_access_cpu, ram_dly, rff1, reset: std_logic;

        signal address, data_read, data_write, data_read_boot, data_read_ram, irq_vector_cpu, inst_addr_cpu, inst_in_cpu, data_addr_cpu, data_in_cpu, data_out_cpu: std_logic_vector(31 downto 0);

        signal ext_irq: std_logic_vector(7 downto 0);

        signal data_we, data_w_cpu: std_logic_vector(3 downto 0);

        signal we_n_next    : std_logic;

        signal we_n_reg     : std_logic;

        signal data_reg     : std_logic_vector(31 downto 0);

begin

        -- clock divider (25MHz clock from 50MHz main clock for Spartan3 Starter Kit)

        process (reset_in, clk_in, clock, we_n_next)

        begin

                if reset_in = '1' then

                        clock <= '0';

                else

                        if clk_in'event and clk_in='1' then

                                clock <= not clock;

                        end if;

                end if;

                if reset_in = '1' then

                        we_n_reg <= '1';

                elsif rising_edge(clk_in) then

                        we_n_reg <= we_n_next or not clock;

                end if;

                if reset_in = '1' then

                        data_read_ram <= (others => '0');

                elsif rising_edge(clock) then

                        data_read_ram <= ram_data;

                end if;

        end process;

        -- reset synchronizer

        process (clock, reset_in)

        begin

                if (reset_in = '1') then

                        rff1 <= '1';

                        reset <= '1';

                elsif (clock'event and clock = '1') then

                        rff1 <= '0';

                        reset <= rff1;

                end if;

        end process;

        process (reset, clock, ext_irq, ram_enable_n)

        begin

                if reset = '1' then

                        ram_dly <= '0';

                        ext_irq <= x"00";

                elsif clock'event and clock = '1' then

                        ram_dly <= not ram_enable_n;

                        ext_irq <= "0000000" & int_in;

                end if;

        end process;

        stall <= '0';

        boot_enable <= '1' when address(31 downto 28) = "0000" else '0';

        data_read <= data_read_boot when address(31 downto 28) = "0000" and ram_dly = '0' else data_read_ram;

        -- HF-RISC core

        core: entity work.datapath

        port map(       clock => clock,

                        reset => reset,

                        stall => stall_cpu,

                        busy => busy_cpu,

                        irq_vector => irq_vector_cpu,

                        irq => irq_cpu,

                        irq_ack => irq_ack_cpu,

                        inst_addr => inst_addr_cpu,

                        inst_in => inst_in_cpu,

                        data_addr => data_addr_cpu,

                        data_in => data_in_cpu,

                        data_out => data_out_cpu,

                        data_w => data_w_cpu,

                        data_access => data_access_cpu

        );

        -- peripherals / busmux logic

        peripherals_busmux: entity work.busmux

        generic map(

                uart_support => uart_support

        )

        port map(

                clock => clock,

                reset => reset,

                stall => stall,

                stall_cpu => stall_cpu,

                busy_cpu => busy_cpu,

                irq_vector_cpu => irq_vector_cpu,

                irq_cpu => irq_cpu,

                irq_ack_cpu => irq_ack_cpu,

                inst_addr_cpu => inst_addr_cpu,

                inst_in_cpu => inst_in_cpu,

                data_addr_cpu => data_addr_cpu,

                data_in_cpu => data_in_cpu,

                data_out_cpu => data_out_cpu,

                data_w_cpu => data_w_cpu,

                data_access_cpu => data_access_cpu,

                addr_mem => address,

                data_read_mem => data_read,

                data_write_mem => data_write,

                data_we_mem => data_we,

                extio_in => ext_irq,

                extio_out => open,

                uart_read => uart_read,

                uart_write => uart_write

        );

        -- instruction and data memory (boot RAM)

        boot_ram: entity work.ram

        generic map (memory_type => "DEFAULT")

        port map (

                clk                     => clock,

                enable                  => boot_enable,

                write_byte_enable       => "0000",

                address                 => address(31 downto 2),

                data_write              => (others => '0'),

                data_read               => data_read_boot

        );

        -- instruction and data memory (external SRAM)

        -- very simple SRAM memory controller using both IS61LV25616AL chips.

        -- these SRAMs have 16-bit words, so we use both chips and access each using low and

        -- high banks. using this arrangement, we have byte addressable 32-bit words.

        -- the address bus is controlled directly by the CPU.

        ram_enable_n <= '0' when address(31 downto 28) = "0100" else '1';

        ram_address <= address(31 downto 2);

        ram_we_n <= we_n_reg;

        ram_control:

        process(clock, ram_enable_n, data_we, data_write)

        begin

                if ram_enable_n = '0' then                       --SRAM

                        ram_ce1_n <= '0';

                        ram_ce2_n <= '0';

                        if data_we = "0000" then                -- read

                                ram_data  <= (others => 'Z');

                                ram_ub1_n <= '0';

                                ram_lb1_n <= '0';

                                ram_ub2_n <= '0';

                                ram_lb2_n <= '0';

                                we_n_next <= '1';

                                ram_oe_n  <= '0';

                        else                                    -- write

                                if clock = '1' then

                                        ram_data <= (others => 'Z');

                                else

                                        ram_data <= data_write;

                                end if;

                                ram_ub1_n <= not data_we(3);

                                ram_lb1_n <= not data_we(2);

                                ram_ub2_n <= not data_we(1);

                                ram_lb2_n <= not data_we(0);

                                we_n_next <= '0';

                                ram_oe_n  <= '1';

                        end if;

                else

                        ram_data <= (others => 'Z');

                        ram_ce1_n <= '1';

                        ram_ub1_n <= '1';

                        ram_lb1_n <= '1';

                        ram_ce2_n <= '1';

                        ram_ub2_n <= '1';

                        ram_lb2_n <= '1';

                        we_n_next <= '1';

                        ram_oe_n  <= '1';

                end if;

        end process;

end interface;