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sdram.v
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sdram.v
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/*
* mt48lc16m16a2_ctrl - A sdram controller
*
* Copyright (C) 2022 Hirosh Dabui <hirosh@dabui.de>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
`default_nettype none `timescale 1ns / 1ps
// ===============================
// 16Mx16 = 32MByte
// Row addressing 8k (A0-A12)
// Bank Switching 4 (BA0, BA1)
// Column Addressing 512 (A0-A8)
// ===============================
module sdram #(
parameter SDRAM_CLK_FREQ = 64,
parameter TRP_NS = 20,
parameter TRC_NS = 66,
parameter TRCD_NS = 20,
parameter TCH_NS = 2,
parameter CAS = 3'd2
) (
input wire clk,
input wire resetn,
`ifdef EN_SDRAM_64MB
input wire [25:0] addr,
`else
input wire [24:0] addr,
`endif
input wire [31:0] din,
input wire [3:0] wmask,
input wire valid,
output reg [31:0] dout,
output reg ready,
output wire sdram_clk,
output wire sdram_cke,
output wire [1:0] sdram_dqm,
output wire [12:0] sdram_addr, // A0-A12 row address, A0-A8 column address
output wire [1:0] sdram_ba, // bank select A11,A12
output wire sdram_csn,
output wire sdram_wen,
output wire sdram_rasn,
output wire sdram_casn,
inout wire [15:0] sdram_dq
);
localparam ONE_MICROSECOND = SDRAM_CLK_FREQ;
localparam WAIT_100US = 100 * ONE_MICROSECOND; // 64 * 1/64e6 = 1us => 100 * 1us
// command period; PRE to ACT in ns, e.g. 20ns
localparam TRP = $rtoi((TRP_NS * ONE_MICROSECOND / 1000) + 1);
// tRC command period (REF to REF/ACT TO ACT) in ns
localparam TRC = $rtoi((TRC_NS * ONE_MICROSECOND / 1000) + 1); //
// tRCD active command to read/write command delay; row-col-delay in ns
localparam TRCD = $rtoi((TRCD_NS * ONE_MICROSECOND / 1000) + 1);
// tCH command hold time
localparam TCH = $rtoi((TCH_NS * ONE_MICROSECOND / 1000) + 1);
initial begin
$display("Clk frequence: %d MHz", SDRAM_CLK_FREQ);
$display("WAIT_100US: %d cycles", WAIT_100US);
$display("TRP: %d cycles", TRP);
$display("TRC: %d cycles", TRC);
$display("TRCD: %d cycles", TRCD);
$display("TCH: %d cycles", TCH);
$display("CAS_LATENCY: %d cycles", CAS_LATENCY);
end
localparam BURST_LENGTH = 3'b001; // 000=1, 001=2, 010=4, 011=8
localparam ACCESS_TYPE = 1'b0; // 0=sequential, 1=interleaved
localparam CAS_LATENCY = CAS; // 2/3 allowed, tRCD=20ns -> 3 cycles@128MHz
localparam OP_MODE = 2'b00; // only 00 (standard operation) allowed
localparam NO_WRITE_BURST = 1'b0; // 0= write burst enabled, 1=only single access write
localparam sdram_mode = {1'b0, NO_WRITE_BURST, OP_MODE, CAS_LATENCY, ACCESS_TYPE, BURST_LENGTH};
//
// ISSI-IS425 datasheet page 16
// (CS, RAS, CAS, WE)
localparam CMD_MRS = 4'b0000; // mode register set
localparam CMD_ACT = 4'b0011; // bank active
localparam CMD_READ = 4'b0101; // to have read variant with autoprecharge set A10=H
localparam CMD_WRITE = 4'b0100; // A10=H to have autoprecharge
localparam CMD_BST = 4'b0110; // burst stop
localparam CMD_PRE = 4'b0010; // precharge selected bank, A10=H both banks
localparam CMD_REF = 4'b0001; // auto refresh (cke=H), selfrefresh assign cke=L
localparam CMD_NOP = 4'b0111;
localparam CMD_DSEL = 4'b1xxx;
reg [3:0] command;
reg [3:0] command_nxt;
reg cke;
reg cke_nxt;
reg [1:0] dqm;
reg [12:0] saddr;
reg [12:0] saddr_nxt;
reg [1:0] ba;
reg [1:0] ba_nxt;
assign sdram_clk = clk;
assign sdram_cke = cke;
assign sdram_addr = saddr;
assign sdram_dqm = dqm;
assign {sdram_csn, sdram_rasn, sdram_casn, sdram_wen} = command;
// assign sdram_ba = ba_nxt;
assign sdram_ba = ba;
// state machine stuff
localparam RESET = 0;
localparam ASSERT_CKE = 1;
localparam INIT_SEQ_PRE_CHARGE_ALL = 2;
localparam INIT_SEQ_AUTO_REFRESH0 = 3;
localparam INIT_SEQ_AUTO_REFRESH1 = 4;
localparam INIT_SEQ_LOAD_MODE = 5;
localparam IDLE = 6;
localparam COL_READ = 7;
localparam COL_READL = 8;
localparam COL_READH = 9;
localparam COL_WRITEL = 10;
localparam COL_WRITEH = 11;
localparam AUTO_REFRESH = 12;
localparam PRE_CHARGE_ALL = 13;
localparam WAIT_STATE = 14;
localparam LAST_STATE = 15;
localparam STATE_WIDTH = $clog2(LAST_STATE);
reg [STATE_WIDTH -1:0] state;
reg [STATE_WIDTH -1:0] state_nxt;
reg [STATE_WIDTH -1:0] ret_state;
reg [STATE_WIDTH -1:0] ret_state_nxt;
localparam WAIT_STATE_WIDTH = $clog2(WAIT_100US);
reg [WAIT_STATE_WIDTH -1:0] wait_states;
reg [WAIT_STATE_WIDTH -1:0] wait_states_nxt;
reg ready_nxt;
reg [31:0] dout_nxt;
reg [1:0] dqm_nxt;
reg update_ready;
reg update_ready_nxt;
reg [15:0] dq;
reg [15:0] dq_nxt;
assign sdram_dq = oe ? dq : 16'hz;
reg oe;
reg oe_nxt;
always @(posedge clk) begin
if (~resetn) begin
state <= RESET;
ret_state <= RESET;
ready <= 1'b0;
wait_states <= 0;
dout <= 0;
command <= CMD_NOP;
dqm <= 2'b11;
dq <= 0;
ba <= 2'b11;
oe <= 1'b0;
saddr <= 0;
update_ready <= 1'b0;
end else begin
dq <= dq_nxt;
dout <= dout_nxt;
state <= state_nxt;
ready <= ready_nxt;
dqm <= dqm_nxt;
cke <= cke_nxt;
command <= command_nxt;
wait_states <= wait_states_nxt;
ret_state <= ret_state_nxt;
ba <= ba_nxt;
oe <= oe_nxt;
saddr <= saddr_nxt;
update_ready <= update_ready_nxt;
end
end
always @(*) begin
wait_states_nxt = wait_states;
state_nxt = state;
ready_nxt = ready;
ret_state_nxt = ret_state;
dout_nxt = dout;
command_nxt = command;
cke_nxt = cke;
saddr_nxt = saddr;
ba_nxt = ba;
dqm_nxt = dqm;
oe_nxt = oe;
dq_nxt = dq;
update_ready_nxt = update_ready;
case (state)
RESET: begin
cke_nxt = 1'b0;
wait_states_nxt = WAIT_100US;
ret_state_nxt = ASSERT_CKE;
state_nxt = WAIT_STATE;
end
ASSERT_CKE: begin
cke_nxt = 1'b1;
wait_states_nxt = 2;
ret_state_nxt = INIT_SEQ_PRE_CHARGE_ALL;
state_nxt = WAIT_STATE;
end
INIT_SEQ_PRE_CHARGE_ALL: begin
cke_nxt = 1'b1;
command_nxt = CMD_PRE;
saddr_nxt[10] = 1'b1;
wait_states_nxt = TRP;
ret_state_nxt = INIT_SEQ_AUTO_REFRESH0;
state_nxt = WAIT_STATE;
end
INIT_SEQ_AUTO_REFRESH0: begin
command_nxt = CMD_REF;
wait_states_nxt = TRC;
ret_state_nxt = INIT_SEQ_AUTO_REFRESH1;
state_nxt = WAIT_STATE;
end
INIT_SEQ_AUTO_REFRESH1: begin
command_nxt = CMD_REF;
wait_states_nxt = TRC;
ret_state_nxt = INIT_SEQ_LOAD_MODE;
state_nxt = WAIT_STATE;
end
INIT_SEQ_LOAD_MODE: begin
command_nxt = CMD_MRS;
saddr_nxt = sdram_mode;
wait_states_nxt = TCH;
ret_state_nxt = IDLE;
state_nxt = WAIT_STATE;
end
IDLE: begin
oe_nxt = 1'b0;
dqm_nxt = 2'b11;
ready_nxt = 1'b0;
if (valid && !ready) begin
command_nxt = CMD_ACT;
`ifdef EN_SDRAM_64MB
ba_nxt = addr[23:22];
saddr_nxt = {addr[25:24], addr[21:11]};
`else
ba_nxt = addr[22:21];
saddr_nxt = {addr[24:23], addr[20:10]};
`endif
wait_states_nxt = TRCD;
ret_state_nxt = |wmask ? COL_WRITEL : COL_READ;
update_ready_nxt = 1'b1;
state_nxt = WAIT_STATE;
end else begin
/* autorefresh */
command_nxt = CMD_REF;
saddr_nxt = 0;
ba_nxt = 0;
wait_states_nxt = 3; //TRC;
ret_state_nxt = IDLE;
update_ready_nxt = 1'b0;
state_nxt = WAIT_STATE;
end
end
COL_READ: begin
command_nxt = CMD_READ;
dqm_nxt = 2'b00;
saddr_nxt = {3'b001, addr[10:2], 1'b0}; // autoprecharge and column
`ifdef EN_SDRAM_64MB
ba_nxt = addr[23:22];
`else
ba_nxt = addr[22:21];
`endif
wait_states_nxt = CAS_LATENCY;
ret_state_nxt = COL_READL;
state_nxt = WAIT_STATE;
end
COL_READL: begin
command_nxt = CMD_NOP;
dqm_nxt = 2'b00;
dout_nxt[15:0] = sdram_dq;
//wait_states_nxt = TRP;
// ret_state_nxt = COL_READH;
state_nxt = COL_READH;
end
COL_READH: begin
command_nxt = CMD_NOP;
dqm_nxt = 2'b00;
dout_nxt[31:16] = sdram_dq;
wait_states_nxt = TRP;
update_ready_nxt = 1'b1;
ret_state_nxt = IDLE;
state_nxt = WAIT_STATE;
end
COL_WRITEL: begin
command_nxt = CMD_WRITE;
dqm_nxt = ~wmask[1:0];
saddr_nxt = {3'b001, addr[10:2], 1'b0}; // autoprecharge and column
`ifdef EN_SDRAM_64MB
ba_nxt = addr[23:22];
`else
ba_nxt = addr[22:21];
`endif
dq_nxt = din[15:0];
oe_nxt = 1'b1;
//wait_states_nxt = TRP;
//ret_state_nxt = COL_WRITEH;
state_nxt = COL_WRITEH;
end
COL_WRITEH: begin
command_nxt = CMD_NOP;
dqm_nxt = ~wmask[3:2];
saddr_nxt = {3'b001, addr[10:2], 1'b0}; // autoprecharge and column
`ifdef EN_SDRAM_64MB
ba_nxt = addr[23:22];
`else
ba_nxt = addr[22:21];
`endif
dq_nxt = din[31:16];
oe_nxt = 1'b1;
wait_states_nxt = TRP;
update_ready_nxt = 1'b1;
ret_state_nxt = IDLE;
state_nxt = WAIT_STATE;
end
PRE_CHARGE_ALL: begin
command_nxt = CMD_PRE;
saddr_nxt[10] = 1'b1; // select all banks
ba_nxt = 0;
wait_states_nxt = TRP;
ret_state_nxt = IDLE;
state_nxt = WAIT_STATE;
end
WAIT_STATE: begin
command_nxt = CMD_NOP;
wait_states_nxt = wait_states - 1;
if (wait_states == 1) begin
state_nxt = ret_state;
if (ret_state == IDLE && update_ready) begin
update_ready_nxt = 1'b0;
ready_nxt = 1'b1;
end
end
end
default: begin
state_nxt = state;
end
endcase
end
endmodule