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-- sdram_controller.vhdl -- Interface for 16-bit SDRAM (non-DDR).

--

-- This module has been tested with a PSC A2V64S40 chip (equivalent to ISSI's

-- IS42S16400). Many parameters are still hardcoded (see below) including the

-- number of banks.

--------------------------------------------------------------------------------

-- To Be Done:

-- 1) CL and BL are hardcoded, generics are ignored.

-- 2) Column width is partially hardcoded (see 'column' signal).

-- 3) Auto-refresh logic is missing.

-- 4) No. of banks is hardcoded to 4.

--

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-- Copyright (C) 2011 Jose A. Ruiz

--                                                              

-- This source file may be used and distributed without         

-- restriction provided that this copyright statement is not    

-- removed from the file and that any derivative work contains  

-- the original copyright notice and the associated disclaimer. 

--                                                              

-- This source file is free software; you can redistribute it   

-- and/or modify it under the terms of the GNU Lesser General   

-- Public License as published by the Free Software Foundation; 

-- either version 2.1 of the License, or (at your option) any   

-- later version.                                               

--                                                              

-- This source is distributed in the hope that it will be       

-- useful, but WITHOUT ANY WARRANTY; without even the implied   

-- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      

-- PURPOSE.  See the GNU Lesser General Public License for more 

-- details.                                                     

--                                                              

-- You should have received a copy of the GNU Lesser General    

-- Public License along with this source; if not, download it   

-- from http://www.opencores.org/lgpl.shtml

--------------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

package sdram_pkg is

-- Record with all SDRAM control lines; all are outputs, data lines are excluded

type sdram_control_t is

record

    addr            : std_logic_vector(11 downto 0);

    ba              : std_logic_vector(1 downto 0);

    ldqm            : std_logic;

    udqm            : std_logic;

    ras_n           : std_logic;

    cas_n           : std_logic;

    cke             : std_logic;

    we_n            : std_logic;

    cs_n            : std_logic;

end record sdram_control_t;

type sdram_command_t is (

    cmd_inhibit,

    cmd_nop,

    cmd_active,

    cmd_read,

    cmd_reada,

    cmd_write,

    cmd_writea,

    cmd_burst_terminate,

    cmd_precharge,

    cmd_auto_refresh,

    cmd_self_refresh,

    cmd_load_mode_register

   );

end package sdram_pkg;

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

use work.sdram_pkg.all;

entity sdram_controller is

    generic (

        CLOCK_PERIOD    : integer := 20; -- Tclk in ns; for reset delay counters

        LATENCY         : integer := 2; -- CAS latency in clock cycles

        BURST           : integer := 8; -- Rd Burst Length in clock cycles

        ROW_WIDTH       : integer := 12;

        COL_WIDTH       : integer := 8

    );

    port (

    clk                 : in std_logic;

    reset               : in std_logic;

    -- ***** Cache interface

    data_rd             : out std_logic_vector(31 downto 0);

    data_wr             : in std_logic_vector(31 downto 0);

    data_addr           : in std_logic_vector(31 downto 2);

    enable              : in std_logic;

    byte_we             : in std_logic_vector(3 downto 0);

    rd                  : in std_logic;

    wr                  : in std_logic;

    busy                : out std_logic;

    done                : out std_logic;

    rd_data_valid       : out std_logic;

    burst_addr          : out std_logic_vector(2 downto 0); --@note1

    -- ***** DRAM interface pins (Tristate buffers not included)

    dram_control        : out sdram_control_t;

    dram_clk            : out std_logic;

    dram_dq_out         : out std_logic_vector(15 downto 0);

    dram_dq_in          : in std_logic_vector(15 downto 0)

    );

end sdram_controller;

architecture simple of sdram_controller is

type sdram_state_t is (

    --**** Chip initialization states

    init_reset,             -- initial state

    init_wait_for_clock,    -- waiting for power & clock to stabilize

    init_wait_for_chip,     -- waiting for SDRAM chip to reset

    init_precharge_all,     -- Issue PALL

    init_wait_trp,          -- Wait for command latency

    init_autorefresh,       -- Issue SELF command

    init_wait_trfc_0,       -- Wait for command latency

    init_wait_trfc_1,       -- Wait for command latency

    init_wait_trfc_2,       -- Wait for command latency

    init_wait_trfc_3,       -- Wait for command latency

    init_load_mode_reg,     -- Issue LMR command

    init_wait_tmrd_0,       -- Wait for command latency

    init_wait_tmrd_1,       -- Wait for command latency

    init_wait_tmrd_2,       -- Wait for command latency

    --**** States for write operation *******************************

    -- Activate target row

    write_00_act,           -- Issue ACT command

    write_01_act_wait,      -- Wait for command latency

    write_02_act_wait,      -- Wait for command latency

    -- Actual write cycles

    write_03_whi,           -- Write high halfword

    write_04_wlo,           -- Write low halfword, with autoprecharge

    write_05_pre_wait,      -- Wait for autoprecharge delay (tRP)

    write_06_pre_wait,      -- 

    write_07_pre_wait,      -- 

    idle,                   -- Waiting for r/w request

    --**** states for read operation ********************************

    -- Activate target row

    read_00_act,            -- Issue ACT command

    read_01_act_wait,       -- Wait for command latency

    read_02_act_wait,       -- Wait for command latency

    -- Read burst

    read_03_rd,             -- Issue READ command with autoprecharge

    read_04_rd_wait,        -- Wait for command latency

    read_05_rd_wait,        -- Wait for command latency

    read_06_rd_w0hi,        -- On bus: Word 0, HI

    read_07_rd_w0lo,        -- On bus: Word 0, LO

    read_08_rd_w1hi,        -- On bus: Word 1, HI

    read_09_rd_w1lo,        -- On bus: Word 1, LO

    read_10_rd_w2hi,        -- On bus: Word 2, HI

    read_11_rd_w2lo,        -- On bus: Word 2, LO

    read_12_rd_w3hi,        -- On bus: Word 3, HI

    read_13_rd_w3lo,        -- On bus: Word 3, LO

    void

   );

signal ps, ns :             sdram_state_t;

signal ctr_pause :          integer range 0 to 16383;

signal end_pause :          std_logic;

signal ddr_command :        sdram_command_t;

signal command_code :       std_logic_vector(3 downto 0);

signal end_autorefresh_loop : std_logic;

signal ctr_auto_refresh :   integer range 0 to 15;

signal byte_we_reg :        std_logic_vector(3 downto 0); --

signal data_wr_reg :        std_logic_vector(31 downto 0); --

signal data_rd_reg :        std_logic_vector(31 downto 0);

signal addr_reg :           std_logic_vector(31 downto 2);

signal load_hw_hi :         std_logic;

signal load_hw_lo :         std_logic;

signal row :                std_logic_vector(11 downto 0);

signal column :             std_logic_vector(9 downto 0);

signal bank :               std_logic_vector(1 downto 0);

signal halfword_addr :      std_logic;

begin

state_machine_reg:

process(clk)

begin

    if clk'event and clk='1' then

        if reset='1' then

            ps <= init_reset;

        else

            ps <= ns;

        end if;

    end if;

end process state_machine_reg;

state_machine_transitions:

process(ps,end_pause,end_autorefresh_loop, rd, byte_we, enable)

begin

    case ps is

    when init_reset =>

        ns <= init_wait_for_clock;

    when init_wait_for_clock =>

        if end_pause='1' then

            ns <= init_wait_for_chip;

        else

            ns <= ps;

        end if;

    when init_wait_for_chip =>

        if end_pause='1' then

            ns <= init_precharge_all;

        else

            ns <= ps;

        end if;

    when init_precharge_all =>

        ns <= init_wait_trp;

    when init_wait_trp =>

        ns <= init_autorefresh;

    when init_autorefresh =>

        ns <= init_wait_trfc_0;

    when init_wait_trfc_0 =>

        ns <= init_wait_trfc_1;

    when init_wait_trfc_1 =>

        ns <= init_wait_trfc_2;

    when init_wait_trfc_2 =>

        ns <= init_wait_trfc_3;

    when init_wait_trfc_3 =>

        ns <= init_load_mode_reg;

    when init_load_mode_reg =>

        ns <= init_wait_tmrd_0;

    when init_wait_tmrd_0 =>

        ns <= init_wait_tmrd_1;

    when init_wait_tmrd_1 =>

        ns <= init_wait_tmrd_2;

    when init_wait_tmrd_2 =>

        ns <= idle;

    when idle =>

        if rd='1' then

            ns <= read_00_act;

        elsif wr='1' then

            ns <= write_00_act;

        else

            ns <= ps;

        end if;

    when write_00_act =>

        ns <= write_01_act_wait;

    when write_01_act_wait =>

        ns <= write_02_act_wait;

    when write_02_act_wait =>

        ns <= write_03_whi;

    when write_03_whi =>

        ns <= write_04_wlo;

    when write_04_wlo =>

        ns <= write_05_pre_wait;

    when write_05_pre_wait =>

        ns <= write_06_pre_wait;

    when write_06_pre_wait =>

        ns <= write_07_pre_wait;

    when write_07_pre_wait =>

        ns <= idle;

    when read_00_act =>

        ns <= read_01_act_wait;

    when read_01_act_wait =>

        ns <= read_02_act_wait;

    when read_02_act_wait =>

        ns <= read_03_rd;

    when read_03_rd =>

        ns <= read_04_rd_wait;

    when read_04_rd_wait => -- FIXME RD burst latency hardcoded

        --ns <= read_05_rd_wait;

        ns <= read_06_rd_w0hi;

    when read_05_rd_wait =>

        ns <= read_06_rd_w0hi;

    when read_06_rd_w0hi =>

        ns <= read_07_rd_w0lo;

    when read_07_rd_w0lo =>

        ns <= read_08_rd_w1hi;

    when read_08_rd_w1hi =>

        ns <= read_09_rd_w1lo;

    when read_09_rd_w1lo =>

        ns <= read_10_rd_w2hi;

    when read_10_rd_w2hi =>

        ns <= read_11_rd_w2lo;

    when read_11_rd_w2lo =>

        ns <= read_12_rd_w3hi;

    when read_12_rd_w3hi =>

        ns <= read_13_rd_w3lo;

    when read_13_rd_w3lo =>

        ns <= idle;

    when void =>

        ns <= void;

    when others =>

        ns <= init_reset;

    end case;

end process state_machine_transitions;

with ps select ddr_command <=

    cmd_precharge           when init_precharge_all,

    cmd_auto_refresh        when init_autorefresh,

    cmd_load_mode_register  when init_load_mode_reg,

    cmd_active              when read_00_act,

    cmd_active              when write_00_act,

    cmd_write               when write_03_whi,

    cmd_writea              when write_04_wlo,

    cmd_reada               when read_03_rd,

    cmd_nop                 when others;

-- assert 'busy' when the controller is idle

with ps select busy <=

    '0' when idle,

    '1' when others;

-- assert 'done' for 1 cycle when current operation ends, before clearing 'busy'

with ps select done <=

    '1' when init_wait_tmrd_2,

    '1' when read_13_rd_w3lo,

    '1' when write_07_pre_wait,

    '0' when others;

--%%%%% Counters %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

pause_counter:

process(clk)

begin

    if clk'event and clk='1' then

        if ps=init_reset then

            ctr_pause <= 20000 / CLOCK_PERIOD; -- 20 us -- clock & vcc stable

        elsif ps=init_wait_for_clock then

            if ctr_pause/=0 then

                ctr_pause <= ctr_pause - 1;

            else

                ctr_pause <= 1000 / CLOCK_PERIOD; -- 1 us -- chip reset

            end if;

        elsif ps=init_wait_for_chip then

            if ctr_pause/=0 then

                ctr_pause <= ctr_pause - 1;

            end if;

        end if;

    end if;

end process pause_counter;

end_pause <= '1' when ctr_pause=0 else '0';

-- FIXME auto-refresh control logic missing

--init_auto_refresh_counter:

--process(clk)

--begin

--    if clk'event and clk='1' then

--        if ps=init_reset then

--            ctr_auto_refresh <= 10;

--        else

--            if ps=init_wait_trfc_3 and ctr_auto_refresh /= 0 then

--                ctr_auto_refresh <= ctr_auto_refresh - 1;

--            end if;

--        end if;

--    end if;

--end process init_auto_refresh_counter;

--

--end_autorefresh_loop <= '1' when ctr_auto_refresh = 0 else '0';

--%%%%% Interface registers %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

cpu_interface_registers:

process(clk)

begin

    if clk'event and clk='1' then

        if ps=idle then

            if rd='1' or byte_we/="0000" then

                data_wr_reg <= data_wr;

                addr_reg <= data_addr;

                byte_we_reg <= byte_we;

            end if;

        end if;

    end if;

end process cpu_interface_registers;

halfword_addr <= '1' when ps=write_04_wlo else '0';

-- FIXME zero-padding is not parametrized

column  <= "00" & addr_reg(COL_WIDTH downto 2) & halfword_addr;

row     <= addr_reg(COL_WIDTH+ROW_WIDTH downto COL_WIDTH+1);

bank    <= addr_reg(COL_WIDTH+ROW_WIDTH+2 downto COL_WIDTH+ROW_WIDTH+1);

--%%%%% Control lines %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

with ddr_command select command_code <=

    "1111"          when cmd_inhibit,

    "0111"          when cmd_nop,

    "0011"          when cmd_active,

    "0101"          when cmd_read,

    "0101"          when cmd_reada,

    "0100"          when cmd_write,

    "0100"          when cmd_writea,

    "0110"          when cmd_burst_terminate,

    "0010"          when cmd_precharge,

    "0001"          when cmd_self_refresh,

    "0001"          when cmd_auto_refresh,

    "0000"          when cmd_load_mode_register,

    "1111"          when others;

dram_control.cs_n   <= command_code(3);

dram_control.ras_n  <= command_code(2);

dram_control.cas_n  <= command_code(1);

dram_control.we_n   <= command_code(0);

with ps select dram_control.cke <=

    '0'             when init_reset,

    '1'             when others;

-- FIXME hardcoded BL and CL

with ps select dram_control.addr <=

--   OOAOOLLLTBBB

    "001000100011"  when init_load_mode_reg, -- CL = 2, BL = 8

    "010000000000"  when init_precharge_all, -- A10=1 => Precharge ALL banks

    row             when read_00_act,

    row             when write_00_act,

    "00" & column   when write_03_whi,

    "01" & column   when write_04_wlo,

    "00" & column   when read_03_rd,

    "010000000000"  when others;

dram_control.ba <= bank;

dram_clk <= clk;

-- DQM[0] is '1' when the byte is NOT to be written to

with ps select dram_control.ldqm <=

    not byte_we_reg(2)  when write_03_whi,

    not byte_we_reg(0)  when write_04_wlo,

    '0'                 when others;

-- DQM[1] is '1' when the byte is NOT to be written to

with ps select dram_control.udqm <=

    not byte_we_reg(3)  when write_03_whi,

    not byte_we_reg(1)  when write_04_wlo,

    '0'                 when others;

with ps select dram_dq_out <=

    data_wr_reg(31 downto 16)  when write_03_whi,

    data_wr_reg(15 downto  0)  when others;

data_rd <= data_rd_reg;

with ps select load_hw_hi <=

    '1' when read_06_rd_w0hi,

    '1' when read_08_rd_w1hi,

    '1' when read_10_rd_w2hi,

    '1' when read_12_rd_w3hi,

    '0' when others;

with ps select load_hw_lo <=

    '1' when read_07_rd_w0lo,

    '1' when read_09_rd_w1lo,

    '1' when read_11_rd_w2lo,

    '1' when read_13_rd_w3lo,

    '0' when others;

data_valid_ff:

process(clk)

begin

    if clk'event and clk='1' then

        -- NOTE: no need to reset this FF, will always be valid when read

        rd_data_valid <= load_hw_lo;

    end if;

end process data_valid_ff;

-- Data RD register is split in two 16-bit halves which are loaded separately

data_read_register:

process(clk)

begin

    if clk'event and clk='1' then

        if load_hw_hi='1' then

            data_rd_reg(31 downto 16) <= dram_dq_in;

        end if;

        if load_hw_lo='1' then

            data_rd_reg(15 downto  0) <= dram_dq_in;

        end if;

    end if;

end process data_read_register;

end simple;