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Gyorgy Szombathelyi 2020-01-04 01:00:55 +01:00
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84
common/mist/gen_ram.vhd
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-- -----------------------------------------------------------------------
--
-- Syntiac's generic VHDL support files.
--
-- -----------------------------------------------------------------------
-- Copyright 2005-2008 by Peter Wendrich (pwsoft@syntiac.com)
-- http://www.syntiac.com/fpga64.html
--
-- Modified April 2016 by Dar (darfpga@aol.fr)
-- http://darfpga.blogspot.fr
-- Remove address register when writing
--
-- -----------------------------------------------------------------------
--
-- gen_rwram.vhd
--
-- -----------------------------------------------------------------------
--
-- generic ram.
--
-- -----------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.numeric_std.ALL;
-- -----------------------------------------------------------------------
entity gen_ram is
generic (
dWidth : integer := 8;
aWidth : integer := 10
);
port (
clk : in std_logic;
we : in std_logic;
addr : in std_logic_vector((aWidth-1) downto 0);
d : in std_logic_vector((dWidth-1) downto 0);
q : out std_logic_vector((dWidth-1) downto 0)
);
end entity;
-- -----------------------------------------------------------------------
architecture rtl of gen_ram is
subtype addressRange is integer range 0 to ((2**aWidth)-1);
type ramDef is array(addressRange) of std_logic_vector((dWidth-1) downto 0);
signal ram: ramDef;
signal rAddrReg : std_logic_vector((aWidth-1) downto 0);
signal qReg : std_logic_vector((dWidth-1) downto 0);
begin
-- -----------------------------------------------------------------------
-- Signals to entity interface
-- -----------------------------------------------------------------------
-- q <= qReg;
-- -----------------------------------------------------------------------
-- Memory write
-- -----------------------------------------------------------------------
process(clk)
begin
if rising_edge(clk) then
if we = '1' then
ram(to_integer(unsigned(addr))) <= d;
end if;
end if;
end process;
-- -----------------------------------------------------------------------
-- Memory read
-- -----------------------------------------------------------------------
process(clk)
begin
if rising_edge(clk) then
-- qReg <= ram(to_integer(unsigned(rAddrReg)));
-- rAddrReg <= addr;
---- qReg <= ram(to_integer(unsigned(addr)));
q <= ram(to_integer(unsigned(addr)));
end if;
end process;
--q <= ram(to_integer(unsigned(addr)));
end architecture;

254
common/mist/sdram.sv
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//
// sdram.v
//
// Static RAM controller implementation using SDRAM MT48LC16M16A2
//
// Copyright (c) 2015,2016 Sorgelig
//
// Some parts of SDRAM code used from project:
// http://hamsterworks.co.nz/mediawiki/index.php/Simple_SDRAM_Controller
//
// This source file is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This source file 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// ------------------------------------------
//
// v2.1 - Add universal 8/16 bit mode.
//
module sdram
(
input init, // reset to initialize RAM
input clk, // clock ~100MHz
//
// SDRAM_* - signals to the MT48LC16M16 chip
inout reg [15:0] SDRAM_DQ, // 16 bit bidirectional data bus
output reg [12:0] SDRAM_A, // 13 bit multiplexed address bus
output reg SDRAM_DQML, // two byte masks
output reg SDRAM_DQMH, //
output reg [1:0] SDRAM_BA, // two banks
output SDRAM_nCS, // a single chip select
output SDRAM_nWE, // write enable
output SDRAM_nRAS, // row address select
output SDRAM_nCAS, // columns address select
output SDRAM_CKE, // clock enable
//
input [1:0] wtbt, // 16bit mode: bit1 - write high byte, bit0 - write low byte,
// 8bit mode: 2'b00 - use addr[0] to decide which byte to write
// Ignored while reading.
//
input [24:0] addr, // 25 bit address for 8bit mode. addr[0] = 0 for 16bit mode for correct operations.
output [15:0] dout, // data output to cpu
input [15:0] din, // data input from cpu
input we, // cpu requests write
input rd, // cpu requests read
output reg ready // dout is valid. Ready to accept new read/write.
);
assign SDRAM_nCS = command[3];
assign SDRAM_nRAS = command[2];
assign SDRAM_nCAS = command[1];
assign SDRAM_nWE = command[0];
assign SDRAM_CKE = cke;
// no burst configured
localparam BURST_LENGTH = 3'b000; // 000=1, 001=2, 010=4, 011=8
localparam ACCESS_TYPE = 1'b0; // 0=sequential, 1=interleaved
localparam CAS_LATENCY = 3'd2; // 2 for < 100MHz, 3 for >100MHz
localparam OP_MODE = 2'b00; // only 00 (standard operation) allowed
localparam NO_WRITE_BURST = 1'b1; // 0= write burst enabled, 1=only single access write
localparam MODE = {3'b000, NO_WRITE_BURST, OP_MODE, CAS_LATENCY, ACCESS_TYPE, BURST_LENGTH};
localparam sdram_startup_cycles= 14'd12100;// 100us, plus a little more, @ 100MHz
localparam cycles_per_refresh = 14'd186; // (64000*36)/8192-1 Calc'd as (64ms @ 36MHz)/8192 rose
localparam startup_refresh_max = 14'b11111111111111;
// SDRAM commands
localparam CMD_INHIBIT = 4'b1111;
localparam CMD_NOP = 4'b0111;
localparam CMD_ACTIVE = 4'b0011;
localparam CMD_READ = 4'b0101;
localparam CMD_WRITE = 4'b0100;
localparam CMD_BURST_TERMINATE = 4'b0110;
localparam CMD_PRECHARGE = 4'b0010;
localparam CMD_AUTO_REFRESH = 4'b0001;
localparam CMD_LOAD_MODE = 4'b0000;
reg [13:0] refresh_count = startup_refresh_max - sdram_startup_cycles;
reg [3:0] command = CMD_INHIBIT;
reg cke = 0;
reg [24:0] save_addr;
reg [15:0] data;
assign dout = save_addr[0] ? {data[7:0], data[15:8]} : {data[15:8], data[7:0]};
typedef enum
{
STATE_STARTUP,
STATE_OPEN_1,
STATE_WRITE,
STATE_READ,
STATE_IDLE, STATE_IDLE_1, STATE_IDLE_2, STATE_IDLE_3,
STATE_IDLE_4, STATE_IDLE_5, STATE_IDLE_6, STATE_IDLE_7
} state_t;
state_t state = STATE_STARTUP;
always @(posedge clk) begin
reg old_we, old_rd;
reg [CAS_LATENCY:0] data_ready_delay;
reg [15:0] new_data;
reg [1:0] new_wtbt;
reg new_we;
reg new_rd;
reg save_we = 1;
command <= CMD_NOP;
refresh_count <= refresh_count+1'b1;
data_ready_delay <= {1'b0, data_ready_delay[CAS_LATENCY:1]};
if(data_ready_delay[0]) data <= SDRAM_DQ;
case(state)
STATE_STARTUP: begin
//------------------------------------------------------------------------
//-- This is the initial startup state, where we wait for at least 100us
//-- before starting the start sequence
//--
//-- The initialisation is sequence is
//-- * de-assert SDRAM_CKE
//-- * 100us wait,
//-- * assert SDRAM_CKE
//-- * wait at least one cycle,
//-- * PRECHARGE
//-- * wait 2 cycles
//-- * REFRESH,
//-- * tREF wait
//-- * REFRESH,
//-- * tREF wait
//-- * LOAD_MODE_REG
//-- * 2 cycles wait
//------------------------------------------------------------------------
cke <= 1;
SDRAM_DQ <= 16'bZZZZZZZZZZZZZZZZ;
SDRAM_DQML <= 1;
SDRAM_DQMH <= 1;
SDRAM_A <= 0;
SDRAM_BA <= 0;
// All the commands during the startup are NOPS, except these
if(refresh_count == startup_refresh_max-31) begin
// ensure all rows are closed
command <= CMD_PRECHARGE;
SDRAM_A[10] <= 1; // all banks
SDRAM_BA <= 2'b00;
end else if (refresh_count == startup_refresh_max-23) begin
// these refreshes need to be at least tREF (66ns) apart
command <= CMD_AUTO_REFRESH;
end else if (refresh_count == startup_refresh_max-15)
command <= CMD_AUTO_REFRESH;
else if (refresh_count == startup_refresh_max-7) begin
// Now load the mode register
command <= CMD_LOAD_MODE;
SDRAM_A <= MODE;
end
//------------------------------------------------------
//-- if startup is complete then go into idle mode,
//-- get prepared to accept a new command, and schedule
//-- the first refresh cycle
//------------------------------------------------------
if(!refresh_count) begin
state <= STATE_IDLE;
ready <= 1;
refresh_count <= 0;
end
end
STATE_IDLE_7: state <= STATE_IDLE_6;
STATE_IDLE_6: state <= STATE_IDLE_5;
STATE_IDLE_5: state <= STATE_IDLE_4;
STATE_IDLE_4: state <= STATE_IDLE_3;
STATE_IDLE_3: state <= STATE_IDLE_2;
STATE_IDLE_2: state <= STATE_IDLE_1;
STATE_IDLE_1: begin
SDRAM_DQ <= 16'bZZZZZZZZZZZZZZZZ;
state <= STATE_IDLE;
// mask possible refresh to reduce colliding.
if(refresh_count > cycles_per_refresh) begin
//------------------------------------------------------------------------
//-- Start the refresh cycle.
//-- This tasks tRFC (66ns), so 2 idle cycles are needed @ 36MHz
//------------------------------------------------------------------------
state <= STATE_IDLE_2;
command <= CMD_AUTO_REFRESH;
refresh_count <= refresh_count - cycles_per_refresh + 1'd1;
end
end
STATE_IDLE: begin
// Priority is to issue a refresh if one is outstanding
if(refresh_count > (cycles_per_refresh<<1)) state <= STATE_IDLE_1;
else if(new_rd | new_we) begin
new_we <= 0;
new_rd <= 0;
save_addr<= addr;
save_we <= new_we;
state <= STATE_OPEN_1;
command <= CMD_ACTIVE;
SDRAM_A <= addr[13:1];
SDRAM_BA <= addr[24:23];
end
end
// ACTIVE-to-READ or WRITE delay >20ns (1 cycle @ 36 MHz)(-75)
STATE_OPEN_1: begin
SDRAM_A <= {4'b0010, save_addr[22:14]};
SDRAM_DQML <= save_we & (new_wtbt ? ~new_wtbt[0] : save_addr[0]);
SDRAM_DQMH <= save_we & (new_wtbt ? ~new_wtbt[1] : ~save_addr[0]);
state <= save_we ? STATE_WRITE : STATE_READ;
end
STATE_READ: begin
state <= STATE_IDLE_5;
command <= CMD_READ;
SDRAM_DQ <= 16'bZZZZZZZZZZZZZZZZ;
// Schedule reading the data values off the bus
data_ready_delay[CAS_LATENCY] <= 1;
end
STATE_WRITE: begin
state <= STATE_IDLE_5;
command <= CMD_WRITE;
SDRAM_DQ <= new_wtbt ? new_data : {new_data[7:0], new_data[7:0]};
ready <= 1;
end
endcase
if(init) begin
state <= STATE_STARTUP;
refresh_count <= startup_refresh_max - sdram_startup_cycles;
end
old_we <= we;
old_rd <= rd;
if(we & ~old_we) {ready, new_we, new_data, new_wtbt} <= {1'b0, 1'b1, din, wtbt};
else
if((rd & ~old_rd) || (rd & old_rd & (save_addr != addr))) {ready, new_rd} <= {1'b0, 1'b1};
end
endmodule