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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
entity sdram_ctrl is
port
(
clock_100 : in std_logic;
reset_n : in std_logic;
b_cs_n : in std_logic;
b_rd_n : in std_logic;
b_wr_n : in std_logic;
b_wait_n : out std_logic;
b_addr : in std_logic_vector(15 downto 0);
b_data : inout std_logic_vector(7 downto 0);
sdram_clk : out std_logic;
sdram_cs_n : out std_logic;
sdram_cas_n : out std_logic;
sdram_ras_n : out std_logic;
sdram_we_n : out std_logic;
sdram_cke : out std_logic;
sdram_addr : out std_logic_vector(12 downto 0);
sdram_ba : out std_logic_vector(1 downto 0);
sdram_dq : inout std_logic_vector(15 downto 0);
sdram_dqm : out std_logic_vector(1 downto 0)
);
end entity;
architecture rtl of sdram_ctrl is
signal clock : std_logic;
signal ack_refresh_request : std_logic;
signal refresh_request : std_logic;
subtype uint13_t is integer range 0 to 8191;
signal refresh_counter : uint13_t;
signal init_done : std_logic;
signal i_addr : std_logic_vector(12 downto 0);
signal i_cmd : std_logic_vector(3 downto 0);
subtype uint4_t is integer range 0 to 15;
signal i_count : uint4_t;
subtype uint3_t is integer range 0 to 7;
signal i_next : uint3_t;
signal i_refs : uint3_t;
signal i_state :uint3_t;
constant I_ST_RESET_WAIT : uint3_t:=0;
constant I_ST_PRECHARGE : uint3_t :=1;
constant I_ST_REFRESH : uint3_t :=2;
constant I_ST_WAIT_COUNT : uint3_t :=3;
constant I_ST_SET_MODE : uint3_t :=4;
constant I_ST_DONE : uint3_t :=5;
-- CS_N RAS_N CAS_N WE_N
constant CMD_IGN : std_logic_vector(3 downto 0 ):="1111";
constant CMD_NOP : std_logic_vector(3 downto 0 ):="0111";
constant CMD_READ : std_logic_vector(3 downto 0 ):="0101";
constant CMD_WRIT : std_logic_vector(3 downto 0 ):="0100";
constant CMD_ACTV : std_logic_vector(3 downto 0 ):="0011";
constant CMD_PRE : std_logic_vector(3 downto 0 ):="0010";
constant CMD_REF : std_logic_vector(3 downto 0 ):="0001";
constant CMD_MRS : std_logic_vector(3 downto 0 ):="0000";
signal m_state : std_logic_vector(8 downto 0);
function active_high(constant val : in boolean) return std_logic is begin
if val then
return '1';
else
return '0';
end if;
end function active_high;
begin
clock<=clock_100;
refresh_counter_process: process(reset_n,clock) begin
if reset_n = '0' then
refresh_counter <= 8000;
elsif rising_edge(clock) then
if refresh_counter = 0 then
refresh_counter <= 624;
else
refresh_counter <= refresh_counter - 1;
end if;
end if;
end process;
refresh_request_process: process(reset_n,clock,refresh_counter,refresh_request,init_done,ack_refresh_request) begin
if reset_n = '0' then
refresh_request <= '0';
elsif rising_edge(clock) then
refresh_request <= (active_high(refresh_counter = 0) or refresh_request) and init_done and not ack_refresh_request;
end if;
end process;
init_done_process: process (reset_n,clock,i_state) begin
if reset_n = '0' then
init_done <= '0';
elsif rising_edge(clock) then
init_done <= init_done or active_high(i_state = I_ST_DONE );
end if;
end process;
init_fsm: process (reset_n,clock,i_state,i_count,i_next,refresh_counter) begin
if reset_n = '0' then
i_state <= I_ST_RESET_WAIT;
i_next <= I_ST_RESET_WAIT;
i_cmd <= CMD_IGN;
i_addr <= (others => '1');
i_count <= 0;
elsif rising_edge(clock) then
if i_state = I_ST_RESET_WAIT then
-- after reset wait until the refresh_counter ticks over for RAM to stabalize
i_cmd <= CMD_IGN;
i_refs <= 0;
if refresh_counter=0 then
i_state <= I_ST_PRECHARGE;
end if;
elsif i_state = I_ST_PRECHARGE then
-- precharge all banks, wait one clock, then go to refresh
i_cmd <=CMD_PRE;
i_state <= I_ST_WAIT_COUNT;
i_count <= 1;
i_next <= I_ST_REFRESH;
elsif i_state =I_ST_REFRESH then
-- repeat 7 times { refresh, wait 5 counts }
i_cmd <=CMD_REF;
i_refs <= i_refs + 1;
i_state <= I_ST_WAIT_COUNT;
i_count <= 5;
if i_refs = 7 then
i_next <= I_ST_SET_MODE;
else
i_next <= I_ST_REFRESH;
end if;
elsif i_state = I_ST_WAIT_COUNT then
-- wait i_count ticks then goto state i_next
i_cmd <= CMD_NOP;
if (i_count > 1) then
i_count <= i_count -1;
else
i_state <= i_next;
end if;
elsif i_state=I_ST_SET_MODE then
-- set mode, wait 3 ticks then goto done
i_cmd <= CMD_MRS;
-- reserverd 000
-- opcode burst read/write 0
-- reserved 00
-- cas latency 3 011
-- sequential burst 0
-- burst length 1 000
i_addr <= "0000000110000";
i_count <= 3;
i_next <= I_ST_DONE;
elsif i_state=I_ST_DONE then
i_state <= I_ST_DONE;
else
i_state <= I_ST_RESET_WAIT;
end if;
end if;
end process;
main_fsm: process (reset_n,clock,m_state,refresh_counter) begin
end process;
if reset_n ='0' then
m_state <= M_ST_1;
m_next <= M_ST_1;
m_cmd <= CMD_IGN;
m_bank <= "00";
m_addr <= "0000000000000";
m_data <= "0000000000000000";
m_dqm <= "00";
m_count <= 0;
ack_refresh_request <= 0;
f_pop <= 0;
oe <= 0;
elsif rising_edge(clock) then
if m_state = M_ST_1 then
if active_high(init_done) then
if active_high(refresh_request) then
m_cmd <= CMD_NOP;
else
m_vmd <= CMD_IGN;
end if;
ack_refresh_request <='1';
if active_high(refresh_request) then
m_state <= M_ST_7;
m_next <= M_ST_8;
m_count <= 1;
active_cs_n <= '1';
elsif (not active_high(f_empty)) then
f_pop <= '1';
active_cs_n <= f_cs_n;
active_rnw <= f_rnw;
active_addr <= f_addr;
active_data <= f_data;
m_state <= M_ST_2;
end if;
else
m_addr <= i_addr;
m_state <= M_ST_1;
m_next <= M_ST_1;
m_cmd <= i_cmd;
end if;
elsif m_state = M_ST_2 then
m_state <= M_ST_3;
m_cmd(3) <= csn_decode;
m_cmd(2 downto 0)="111";
m_bank <= active_bank;
m_addr <= active_addr(22 downto 10);
m_data <= active_data;
m_dqm <= active_dqm;
m_count <=2;
if (active_high(active_rnw)) then
m_next <=M_ST_4;
else
m_next <=M_ST_5;
end if;
elsif m_state = M_ST_3
end;
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