基于FPGA的SDRAM控制器设计（2）
基于FPGA的SDRAM的自刷新操作
- SDRAM自刷新简述
- SDRAM自刷新时序图
- SDRAM自刷新代码
- 仿真模块的代码
- 仿真结果测试
- 参考文献
- 总结
SDRAM自刷新简述
SDRAM作为一个RAM并没有断电保存的功能，在操作的SDRAM的时候每隔一段时间必须对SDRAM进行自刷新操作，防止SDRAM中的数据丢失。那么，SDRAM 每两次刷新的间隔是多长时间呢。这个时间需要查找技术手册：
64ms 是电容在未充电的状态下能保持电量的最长时间，也就是 SDRAM 在未刷新的状态下能保存数据的最长时间是 64ms。而SDRAM的书信操作是一行一行刷新的，该SDRAM一共4096行，所以，每两次刷新的时间间隔大约是 64ms / 4096 = 15.625us。 在本项目中， 我们设置刷新间隔为 15us。
由于SDRAM需要同时调控自刷新、读操作、写操作的协调，所以在顶层需要控制三个模块的执行顺序，这三个模块中自刷新命令的优先级最高，但是在执行读写操作时需要等待本次突发结束才可以调到自刷新模块执行，否则就会丢数据。
以刷新操作为例： 当刷新的时间到了之后，刷新模块向仲裁发起刷新请求，然后仲裁老大根据 SDRAM 当前所处的一个状态来判断是否可以允许 SDRAM 进行刷新，当仲裁老大认为 SDRAM 可以刷新了之后，向刷新模块给出刷新使能信号；当刷新模块对 SDRAM 进行刷新完毕后，再向仲裁老大给出刷新结束标志。模块之间的状态转移图如下：
模块间的细节图如下：
这里为了省事直接套用了开源骚客的图形，有不懂的同学可以关注该老师，自己从该老师的课程中学到了很多知识。
SDRAM自刷新时序图
SDRAM刷新模块的时序图如下：
上面的COMMAND是与上电初始化模块相同的四个控制信号。同样需要特别注意A10这个信号，一般是对全部bank进行预充电操作。
SDRAM自刷新代码
这里我们需要在SDRAM的顶层模块补充仲裁模块，所遵循的方式正是上面的状态机，代码如下：
`timescale 1ns / 1ps
// *********************************************************************************
// Project Name : OSXXXX
// Author : zhangningning
// Email : [email protected]
// Website :
// Module Name : sdram_top.v
// Create Time : 2020-02-09 17:22:24
// Editor : sublime text3, tab size (4)
// CopyRight(c) : All Rights Reserved
//
// *********************************************************************************
// Modification History:
// Date By Version Change Description
// -----------------------------------------------------------------------
// XXXX zhangningning 1.0 Original
//
// *********************************************************************************
module sdram_top(
//System Interfaces
input sclk ,
input rst_n ,
//SDRAM Interfaces
output wire sdram_clk ,
output wire sdram_cke ,
output reg sdram_cs_n ,
output reg sdram_cas_n ,
output reg sdram_ras_n ,
output reg sdram_we_n ,
output wire [ 1:0] sdram_bank ,
output reg [11:0] sdram_addr ,
output wire [ 1:0] sdram_dqm ,
inout [15:0] sdram_dq
);
//========================================================================================\
//**************Define Parameter and Internal Signals**********************************
//========================================================================================/
localparam NOP = 4'b0111 ;
localparam IDLE = 5'b0_0001 ;
localparam ARBIT = 5'b0_0010 ;
localparam AREF = 5'b0_0100 ;
localparam WRITE = 5'b0_1000 ;
localparam READ = 5'b1_0000 ;
//sdram_init
wire [ 3:0] init_cmd ;
wire [11:0] init_addr ;
wire init_done ;
//AREF
wire aref_req ;
reg aref_en ;
wire aref_end ;
wire [ 3:0] aref_cmd ;
wire [11:0] aref_addr ;
//WRITE
//READ
//ARBIT
reg [ 4:0] state ;
//========================================================================================\
//************** Main Code **********************************
//========================================================================================/
assign sdram_dqm = 2'b00;
assign sdram_clk = ~sclk;
assign sdram_cke = 1'b1;
assign sdram_bank = 2'b00;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
state <= IDLE;
else case(state)
IDLE : if(init_done == 1'b1)
state <= ARBIT;
else
state <= state;
ARBIT : if(aref_req == 1'b1)
state <= AREF;
else
state <= state;
AREF : if(aref_end == 1'b1)
state <= ARBIT;
else
state <= state;
default : state <= IDLE;
endcase
always @(*)
case(state)
IDLE : begin
sdram_addr <= init_addr;
{sdram_cs_n, sdram_ras_n, sdram_cas_n, sdram_we_n} = init_cmd;
end
AREF : begin
sdram_addr <= aref_addr;
{sdram_cs_n, sdram_ras_n, sdram_cas_n, sdram_we_n} = aref_cmd;
end
default : begin
sdram_addr <= 12'd0;
{sdram_cs_n, sdram_ras_n, sdram_cas_n, sdram_we_n} = NOP;
end
endcase
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_en <= 1'b0;
else if(state == ARBIT && aref_req == 1'b1)
aref_en <= 1'b1;
else
aref_en <= 1'b0;
sdram_init sdram_init_inst(
//System Interfaces
.sclk (sclk ),
.rst_n (rst_n ),
//SDRAM Interfaces
.sdram_cmd (init_cmd ),
.sdram_addr (init_addr ),
//Others
.init_done (init_done )
);
sdram_aref sdram_aref_inst(
//Sysytem Interfaces
.sclk (sclk ),
.rst_n (rst_n ),
//SDRAM Interfaces
.aref_cmd (aref_cmd ),
.aref_addr (aref_addr ),
//Others
.aref_req (aref_req ),
.aref_end (aref_end ),
.aref_en (aref_en ),
.init_done (init_done )
);
endmodule
代码不多，但是要特别注意仲裁状态机的书写，很有借鉴意义。
自刷新模块的代码：
`timescale 1ns / 1ps
// *********************************************************************************
// Project Name : OSXXXX
// Author : zhangningning
// Email : [email protected]
// Website :
// Module Name : sdram_aref.v
// Create Time : 2020-02-10 13:34:03
// Editor : sublime text3, tab size (4)
// CopyRight(c) : All Rights Reserved
//
// *********************************************************************************
// Modification History:
// Date By Version Change Description
// -----------------------------------------------------------------------
// XXXX zhangningning 1.0 Original
//
// *********************************************************************************
module sdram_aref(
//Sysytem Interfaces
input sclk ,
input rst_n ,
//SDRAM Interfaces
output reg [ 3:0] aref_cmd ,
output wire [11:0] aref_addr ,
//Others
input init_done ,
output reg aref_req ,
output reg aref_end ,
input aref_en
);
//========================================================================================\
//**************Define Parameter and Internal Signals**********************************
//========================================================================================/
localparam NOP = 4'b0111 ;
localparam PRE = 4'b0010 ;
localparam AREF = 4'b0001 ;
localparam DELAY_15US = 11'd1500 ;
reg aref_flag ;
reg [ 2:0] cnt_cmd ;
reg [10:0] cnt_15ms ;
//========================================================================================\
//************** Main Code **********************************
//========================================================================================/
assign aref_addr = 12'b0100_0000_0000;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_flag <= 1'b0;
else if(cnt_cmd >= 3'd4)
aref_flag <= 1'b0;
else if(aref_en == 1'b1)
aref_flag <= 1'b1;
else
aref_flag <= aref_flag;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
cnt_cmd <= 3'd0;
else if(cnt_cmd >= 3'd4)
cnt_cmd <= 3'd0;
else if(aref_flag == 1'b1)
cnt_cmd <= cnt_cmd + 1'b1;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_cmd <= NOP;
else case(cnt_cmd)
1 : aref_cmd <= PRE;
4 : aref_cmd <= AREF;
default : aref_cmd <= NOP;
endcase
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_end <= 1'b0;
else if(cnt_cmd >= 3'd4)
aref_end <= 1'b1;
else
aref_end <= 1'b0;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
cnt_15ms <= 20'd0;
else if(cnt_15ms == DELAY_15US)
cnt_15ms <= 20'd0;
else if(init_done == 1'b1)
cnt_15ms <= cnt_15ms + 1'b1;
else
cnt_15ms <= 20'd0;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_req <= 1'b0;
else if(cnt_15ms == DELAY_15US)
aref_req <= 1'b1;
else if(aref_en == 1'b1)
aref_req <= 1'b0;
else
aref_req <= aref_req;
endmodule
为了完整性，这里我们也给出上一节的上电初始化代码：
`timescale 1ns / 1ps
// *********************************************************************************
// Project Name : OSXXXX
// Author : zhangningning
// Email : [email protected]
// Website :
// Module Name : sdram_aref.v
// Create Time : 2020-02-10 13:34:03
// Editor : sublime text3, tab size (4)
// CopyRight(c) : All Rights Reserved
//
// *********************************************************************************
// Modification History:
// Date By Version Change Description
// -----------------------------------------------------------------------
// XXXX zhangningning 1.0 Original
//
// *********************************************************************************
module sdram_aref(
//Sysytem Interfaces
input sclk ,
input rst_n ,
//SDRAM Interfaces
output reg [ 3:0] aref_cmd ,
output wire [11:0] aref_addr ,
//Others
input init_done ,
output reg aref_req ,
output reg aref_end ,
input aref_en
);
//========================================================================================\
//**************Define Parameter and Internal Signals**********************************
//========================================================================================/
localparam NOP = 4'b0111 ;
localparam PRE = 4'b0010 ;
localparam AREF = 4'b0001 ;
localparam DELAY_15US = 11'd1500 ;
reg aref_flag ;
reg [ 2:0] cnt_cmd ;
reg [10:0] cnt_15ms ;
//========================================================================================\
//************** Main Code **********************************
//========================================================================================/
assign aref_addr = 12'b0100_0000_0000;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_flag <= 1'b0;
else if(cnt_cmd >= 3'd4)
aref_flag <= 1'b0;
else if(aref_en == 1'b1)
aref_flag <= 1'b1;
else
aref_flag <= aref_flag;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
cnt_cmd <= 3'd0;
else if(cnt_cmd >= 3'd4)
cnt_cmd <= 3'd0;
else if(aref_flag == 1'b1)
cnt_cmd <= cnt_cmd + 1'b1;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_cmd <= NOP;
else case(cnt_cmd)
1 : aref_cmd <= PRE;
4 : aref_cmd <= AREF;
default : aref_cmd <= NOP;
endcase
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_end <= 1'b0;
else if(cnt_cmd >= 3'd4)
aref_end <= 1'b1;
else
aref_end <= 1'b0;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
cnt_15ms <= 20'd0;
else if(cnt_15ms == DELAY_15US)
cnt_15ms <= 20'd0;
else if(init_done == 1'b1)
cnt_15ms <= cnt_15ms + 1'b1;
else
cnt_15ms <= 20'd0;
always @(posedge sclk or negedge rst_n)
if(rst_n == 1'b0)
aref_req <= 1'b0;
else if(cnt_15ms == DELAY_15US)
aref_req <= 1'b1;
else if(aref_en == 1'b1)
aref_req <= 1'b0;
else
aref_req <= aref_req;
endmodule
仿真模块的代码
其实这里与上一篇文章中仿真模块的代码完全相同，同样为了完整性，给出代码：
顶层测试模块的代码：
`timescale 1ns / 1ps
`define CLOCK 10
// *********************************************************************************
// Project Name : OSXXXX
// Author : zhangningning
// Email : [email protected]
// Website :
// Module Name : sdram_init_tb.v
// Create Time : 2020-02-09 17:10:08
// Editor : sublime text3, tab size (4)
// CopyRight(c) : All Rights Reserved
//
// *********************************************************************************
// Modification History:
// Date By Version Change Description
// -----------------------------------------------------------------------
// XXXX zhangningning 1.0 Original
//
// *********************************************************************************
module sdram_init_tb;
reg sclk ;
reg rst_n ;
wire sdram_clk ;
wire sdram_cke ;
wire sdram_cs_n ;
wire sdram_cas_n ;
wire sdram_ras_n ;
wire sdram_we_n ;
wire [ 1:0] sdram_bank ;
wire [11:0] sdram_addr ;
wire [ 1:0] sdram_dqm ;
wire [15:0] sdram_dq ;
initial begin
sclk = 1'b0;
rst_n <= 1'b0;
#(100*`CLOCK);
rst_n <= 1'b1;
end
always #(`CLOCK/2) sclk = ~sclk;
sdram_top sdram_top_inst(
//System Interfaces
.sclk (sclk ),
.rst_n (rst_n ),
//SDRAM Interfaces
.sdram_clk (sdram_clk ),
.sdram_cke (sdram_cke ),
.sdram_cs_n (sdram_cs_n ),
.sdram_cas_n (sdram_cas_n ),
.sdram_ras_n (sdram_ras_n ),
.sdram_we_n (sdram_we_n ),
.sdram_bank (sdram_bank ),
.sdram_addr (sdram_addr ),
.sdram_dqm (sdram_dqm ),
.sdram_dq (sdram_dq )
);
defparam sdram_model_plus_inst.addr_bits = 12;
defparam sdram_model_plus_inst.data_bits = 16;
defparam sdram_model_plus_inst.col_bits = 9;
defparam sdram_model_plus_inst.mem_sizes = 2*1024*1024; // 2M
sdram_model_plus sdram_model_plus_inst(
.Dq (sdram_dq ),
.Addr (sdram_addr ),
.Ba (sdram_bank ),
.Clk (sdram_clk ),
.Cke (sdram_cke ),
.Cs_n (sdram_cs_n ),
.Ras_n (sdram_ras_n ),
.Cas_n (sdram_cas_n ),
.We_n (sdram_we_n ),
.Dqm (sdram_dqm ),
.Debug (1'b1 )
);
endmodule
仿真模型的代码：
/***************************************************************************************
作者： 李晟
2003-08-27 V0.1 李晟
添加内存模块倒空功能，在外部需要创建事件：sdram_r ,本SDRAM的内容将会按Bank 顺序damp out 至文件
sdram_data.txt 中
×××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××*/
//2004-03-04 陈乃奎 修改原程序中将BANK的数据转存入TXT文件的格式
//2004-03-16 陈乃奎 修改SDRAM 的初始化数据
//2004/04/06 陈乃奎 将SDRAM的操作命令以字符形式表示，以便用MODELSIM监视
//2004/04/19 陈乃奎 修改参数 parameter tAC = 8;
//2010/09/17 罗瑶 修改sdram的大小，数据位宽，dqm宽度;
/****************************************************************************************
*
* File Name: sdram_model.V
* Version: 0.0f
* Date: July 8th, 1999
* Model: BUS Functional
* Simulator: Model Technology (PC version 5.2e PE)
*
* Dependencies: None
*
* Author: Son P. Huynh
* Email: [email protected]
* Phone: (208) 368-3825
* Company: Micron Technology, Inc.
* Model: sdram_model (1Meg x 16 x 4 Banks)
*
* Description: 64Mb SDRAM Verilog model
*
* Limitation: - Doesn't check for 4096 cycle refresh
*
* Note: - Set simulator resolution to "ps" accuracy
* - Set Debug = 0 to disable $display messages
*
* Disclaimer: THESE DESIGNS ARE PROVIDED "AS IS" WITH NO WARRANTY
* WHATSOEVER AND MICRON SPECIFICALLY DISCLAIMS ANY
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
* A PARTICULAR PURPOSE, OR AGAINST INFRINGEMENT.
*
* Copyright ?1998 Micron Semiconductor Products, Inc.
* All rights researved
*
* Rev Author Phone Date Changes
* ---- ---------------------------- ---------- ---------------------------------------
* 0.0f Son Huynh 208-368-3825 07/08/1999 - Fix tWR = 1 Clk + 7.5 ns (Auto)
* Micron Technology Inc. - Fix tWR = 15 ns (Manual)
* - Fix tRP (Autoprecharge to AutoRefresh)
*
* 0.0a Son Huynh 208-368-3825 05/13/1998 - First Release (from 64Mb rev 0.0e)
* Micron Technology Inc.
****************************************************************************************/
`timescale 1ns / 100ps
module sdram_model_plus (Dq, Addr, Ba, Clk, Cke, Cs_n, Ras_n, Cas_n, We_n, Dqm,Debug);
parameter addr_bits = 11;
parameter data_bits = 32;
parameter col_bits = 8;
parameter mem_sizes = 1048576*2-1;//1 Meg
inout [data_bits - 1 : 0] Dq;
input [addr_bits - 1 : 0] Addr;
input [1 : 0] Ba;
input Clk;
input Cke;
input Cs_n;
input Ras_n;
input Cas_n;
input We_n;
input [3 : 0] Dqm; //高低各8bit
//added by xzli
input Debug;
reg [data_bits - 1 : 0] Bank0 [0 : mem_sizes];//存储器类型数据
reg [data_bits - 1 : 0] Bank1 [0 : mem_sizes];
reg [data_bits - 1 : 0] Bank2 [0 : mem_sizes];
reg [data_bits - 1 : 0] Bank3 [0 : mem_sizes];
reg [1 : 0] Bank_addr [0 : 3]; // Bank Address Pipeline
reg [col_bits - 1 : 0] Col_addr [0 : 3]; // Column Address Pipeline
reg [3 : 0] Command [0 : 3]; // Command Operation Pipeline
reg [3 : 0] Dqm_reg0, Dqm_reg1; // DQM Operation Pipeline
reg [addr_bits - 1 : 0] B0_row_addr, B1_row_addr, B2_row_addr, B3_row_addr;
reg [addr_bits - 1 : 0] Mode_reg;
reg [data_bits - 1 : 0] Dq_reg, Dq_dqm;
reg [col_bits - 1 : 0] Col_temp, Burst_counter;
reg Act_b0, Act_b1, Act_b2, Act_b3; // Bank Activate
reg Pc_b0, Pc_b1, Pc_b2, Pc_b3; // Bank Precharge
reg [1 : 0] Bank_precharge [0 : 3]; // Precharge Command
reg A10_precharge [0 : 3]; // Addr[10] = 1 (All banks)
reg Auto_precharge [0 : 3]; // RW AutoPrecharge (Bank)
reg Read_precharge [0 : 3]; // R AutoPrecharge
reg Write_precharge [0 : 3]; // W AutoPrecharge
integer Count_precharge [0 : 3]; // RW AutoPrecharge (Counter)
reg RW_interrupt_read [0 : 3]; // RW Interrupt Read with Auto Precharge
reg RW_interrupt_write [0 : 3]; // RW Interrupt Write with Auto Precharge
reg Data_in_enable;
reg Data_out_enable;
reg [1 : 0] Bank, Previous_bank;
reg [addr_bits - 1 : 0] Row;
reg [col_bits - 1 : 0] Col, Col_brst;
// Internal system clock
reg CkeZ, Sys_clk;
reg [21:0] dd;
// Commands Decode
wire Active_enable = ~Cs_n & ~Ras_n & Cas_n & We_n;
wire Aref_enable = ~Cs_n & ~Ras_n & ~Cas_n & We_n;
wire Burst_term = ~Cs_n & Ras_n & Cas_n & ~We_n;
wire Mode_reg_enable = ~Cs_n & ~Ras_n & ~Cas_n & ~We_n;
wire Prech_enable = ~Cs_n & ~Ras_n & Cas_n & ~We_n;
wire Read_enable = ~Cs_n & Ras_n & ~Cas_n & We_n;
wire Write_enable = ~Cs_n & Ras_n & ~Cas_n & ~We_n;
// Burst Length Decode
wire Burst_length_1 = ~Mode_reg[2] & ~Mode_reg[1] & ~Mode_reg[0];
wire Burst_length_2 = ~Mode_reg[2] & ~Mode_reg[1] & Mode_reg[0];
wire Burst_length_4 = ~Mode_reg[2] & Mode_reg[1] & ~Mode_reg[0];
wire Burst_length_8 = ~Mode_reg[2] & Mode_reg[1] & Mode_reg[0];
// CAS Latency Decode
wire Cas_latency_2 = ~Mode_reg[6] & Mode_reg[5] & ~Mode_reg[4];
wire Cas_latency_3 = ~Mode_reg[6] & Mode_reg[5] & Mode_reg[4];
// Write Burst Mode
wire Write_burst_mode = Mode_reg[9];
wire Debug; // Debug messages : 1 = On; 0 = Off
wire Dq_chk = Sys_clk & Data_in_enable; // Check setup/hold time for DQ
reg [31:0] mem_d;
event sdram_r,sdram_w,compare;
assign Dq = Dq_reg; // DQ buffer
// Commands Operation
`define ACT 0
`define NOP 1
`define READ 2
`define READ_A 3
`define WRITE 4
`define WRITE_A 5
`define PRECH 6
`define A_REF 7
`define BST 8
`define LMR 9
// // Timing Parameters for -75 (PC133) and CAS Latency = 2
// parameter tAC = 8; //test 6.5
// parameter tHZ = 7.0;
// parameter tOH = 2.7;
// parameter tMRD = 2.0; // 2 Clk Cycles
// parameter tRAS = 44.0;
// parameter tRC = 66.0;
// parameter tRCD = 20.0;
// parameter tRP = 20.0;
// parameter tRRD = 15.0;
// parameter tWRa = 7.5; // A2 Version - Auto precharge mode only (1 Clk + 7.5 ns)
// parameter tWRp = 0.0; // A2 Version - Precharge mode only (15 ns)
// Timing Parameters for -7 (PC143) and CAS Latency = 3
parameter tAC = 6.5; //test 6.5
parameter tHZ = 5.5;
parameter tOH = 2;
parameter tMRD = 2.0; // 2 Clk Cycles
parameter tRAS = 48.0;
parameter tRC = 70.0;
parameter tRCD = 20.0;
parameter tRP = 20.0;
parameter tRRD = 14.0;
parameter tWRa = 7.5; // A2 Version - Auto precharge mode only (1 Clk + 7.5 ns)
parameter tWRp = 0.0; // A2 Version - Precharge mode only (15 ns)
// Timing Check variable
integer MRD_chk;
integer WR_counter [0 : 3];
time WR_chk [0 : 3];
time RC_chk, RRD_chk;
time RAS_chk0, RAS_chk1, RAS_chk2, RAS_chk3;
time RCD_chk0, RCD_chk1, RCD_chk2, RCD_chk3;
time RP_chk0, RP_chk1, RP_chk2, RP_chk3;
integer test_file;
//*****display the command of the sdram**************************************
parameter Mode_Reg_Set =4'b0000;
parameter Auto_Refresh =4'b0001;
parameter Row_Active =4'b0011;
parameter Pre_Charge =4'b0010;
parameter PreCharge_All =4'b0010;
parameter Write =4'b0100;
parameter Write_Pre =4'b0100;
parameter Read =4'b0101;
parameter Read_Pre =4'b0101;
parameter Burst_Stop =4'b0110;
parameter Nop =4'b0111;
parameter Dsel =4'b1111;
wire [3:0] sdram_control;
reg cke_temp;
reg [8*13:1] sdram_command;
always@(posedge Clk)
cke_temp<=Cke;
assign sdram_control={Cs_n,Ras_n,Cas_n,We_n};
always@(sdram_control or cke_temp)
begin
case(sdram_control)
Mode_Reg_Set: sdram_command<="Mode_Reg_Set";
Auto_Refresh: sdram_command<="Auto_Refresh";
Row_Active: sdram_command<="Row_Active";
Pre_Charge: sdram_command<="Pre_Charge";
Burst_Stop: sdram_command<="Burst_Stop";
Dsel: sdram_command<="Dsel";
Write: if(cke_temp==1)
sdram_command<="Write";
else
sdram_command<="Write_suspend";
Read: if(cke_temp==1)
sdram_command<="Read";
else
sdram_command<="Read_suspend";
Nop: if(cke_temp==1)
sdram_command<="Nop";
else
sdram_command<="Self_refresh";
default: sdram_command<="Power_down";
endcase
end
//*****************************************************
initial
begin
//test_file=$fopen("test_file.txt");
end
initial
begin
Dq_reg = {data_bits{1'bz}};
{Data_in_enable, Data_out_enable} = 0;
{Act_b0, Act_b1, Act_b2, Act_b3} = 4'b0000;
{Pc_b0, Pc_b1, Pc_b2, Pc_b3} = 4'b0000;
{WR_chk[0], WR_chk[1], WR_chk[2], WR_chk[3]} = 0;
{WR_counter[0], WR_counter[1], WR_counter[2], WR_counter[3]} = 0;
{RW_interrupt_read[0], RW_interrupt_read[1], RW_interrupt_read[2], RW_interrupt_read[3]} = 0;
{RW_interrupt_write[0], RW_interrupt_write[1], RW_interrupt_write[2], RW_interrupt_write[3]} = 0;
{MRD_chk, RC_chk, RRD_chk} = 0;
{RAS_chk0, RAS_chk1, RAS_chk2, RAS_chk3} = 0;
{RCD_chk0, RCD_chk1, RCD_chk2, RCD_chk3} = 0;
{RP_chk0, RP_chk1, RP_chk2, RP_chk3} = 0;
$timeformat (-9, 0, " ns", 12);
//$readmemh("bank0.txt", Bank0);
//$readmemh("bank1.txt", Bank1);
//$readmemh("bank2.txt", Bank2);
//$readmemh("bank3.txt", Bank3);
/*
for(dd=0;dd<=mem_sizes;dd=dd+1)
begin
Bank0[dd]=dd[data_bits - 1 : 0];
Bank1[dd]=dd[data_bits - 1 : 0]+1;
Bank2[dd]=dd[data_bits - 1 : 0]+2;
Bank3[dd]=dd[data_bits - 1 : 0]+3;
end
*/
initial_sdram(0);
end
task initial_sdram;
input data_sign;
reg [3:0] data_sign;
for(dd=0;dd<=mem_sizes;dd=dd+1)
begin
mem_d = {data_sign,data_sign,data_sign,data_sign,data_sign,data_sign,data_sign,data_sign};
if(data_bits==16)
begin
Bank0[dd]=mem_d[15:0];
Bank1[dd]=mem_d[15:0];
Bank2[dd]=mem_d[15:0];
Bank3[dd]=mem_d[15:0];
end
else if(data_bits==32)
begin
Bank0[dd]=mem_d[31:0];
Bank1[dd]=mem_d[31:0];
Bank2[dd]=mem_d[31:0];
Bank3[dd]=mem_d[31:0];
end
end
endtask
// System clock generator
always
begin
@(posedge Clk)
begin
Sys_clk = CkeZ;
CkeZ = Cke;
end
@(negedge Clk)
begin
Sys_clk = 1'b0;
end
end
always @ (posedge Sys_clk) begin
// Internal Commamd Pipelined
Command[0] = Command[1];
Command[1] = Command[2];
Command[2] = Command[3];
Command[3] = `NOP;
Col_addr[0] = Col_addr[1];
Col_addr[1] = Col_addr[2];
Col_addr[2] = Col_addr[3];
Col_addr[3] = {col_bits{1'b0}};
Bank_addr[0] = Bank_addr[1];
Bank_addr[1] = Bank_addr[2];
Bank_addr[2] = Bank_addr[3];
Bank_addr[3] = 2'b0;
Bank_precharge[0] = Bank_precharge[1];
Bank_precharge[1] = Bank_precharge[2];
Bank_precharge[2] = Bank_precharge[3];
Bank_precharge[3] = 2'b0;
A10_precharge[0] = A10_precharge[1];
A10_precharge[1] = A10_precharge[2];
A10_precharge[2] = A10_precharge[3];
A10_precharge[3] = 1'b0;
// Dqm pipeline for Read
Dqm_reg0 = Dqm_reg1;
Dqm_reg1 = Dqm;
// Read or Write with Auto Precharge Counter
if (Auto_precharge[0] == 1'b1) begin
Count_precharge[0] = Count_precharge[0] + 1;
end
if (Auto_precharge[1] == 1'b1) begin
Count_precharge[1] = Count_precharge[1] + 1;
end
if (Auto_precharge[2] == 1'b1) begin
Count_precharge[2] = Count_precharge[2] + 1;
end
if (Auto_precharge[3] == 1'b1) begin
Count_precharge[3] = Count_precharge[3] + 1;
end
// tMRD Counter
MRD_chk = MRD_chk + 1;
// tWR Counter for Write
WR_counter[0] = WR_counter[0] + 1;
WR_counter[1] = WR_counter[1] + 1;
WR_counter[2] = WR_counter[2] + 1;
WR_counter[3] = WR_counter[3] + 1;
// Auto Refresh
if (Aref_enable == 1'b1) begin
if (Debug) $display ("at time %t AREF : Auto Refresh", $time);
// Auto Refresh to Auto Refresh
if (($time - RC_chk < tRC)&&Debug) begin
$display ("at time %t ERROR: tRC violation during Auto Refresh", $time);
end
// Precharge to Auto Refresh
if (($time - RP_chk0 < tRP || $time - RP_chk1 < tRP || $time - RP_chk2 < tRP || $time - RP_chk3 < tRP)&&Debug) begin
$display ("at time %t ERROR: tRP violation during Auto Refresh", $time);
end
// Precharge to Refresh
if (Pc_b0 == 1'b0 || Pc_b1 == 1'b0 || Pc_b2 == 1'b0 || Pc_b3 == 1'b0) begin
$display ("at time %t ERROR: All banks must be Precharge before Auto Refresh", $time);
end
// Record Current tRC time
RC_chk = $time;
end
// Load Mode Register
if (Mode_reg_enable == 1'b1) begin
// Decode CAS Latency, Burst Length, Burst Type, and Write Burst Mode
if (Pc_b0 == 1'b1 && Pc_b1 == 1'b1 && Pc_b2 == 1'b1 && Pc_b3 == 1'b1) begin
Mode_reg = Addr;
if (Debug) begin
$display ("at time %t LMR : Load Mode Register", $time);
// CAS Latency
if (Addr[6 : 4] == 3'b010)
$display (" CAS Latency = 2");
else if (Addr[6 : 4] == 3'b011)
$display (" CAS Latency = 3");
else
$display (" CAS Latency = Reserved");
// Burst Length
if (Addr[2 : 0] == 3'b000)
$display (" Burst Length = 1");
else if (Addr[2 : 0] == 3'b001)
$display (" Burst Length = 2");
else if (Addr[2 : 0] == 3'b010)
$display (" Burst Length = 4");
else if (Addr[2 : 0] == 3'b011)
$display (" Burst Length = 8");
else if (Addr[3 : 0] == 4'b0111)
$display (" Burst Length = Full");
else
$display (" Burst Length = Reserved");
// Burst Type
if (Addr[3] == 1'b0)
$display (" Burst Type = Sequential");
else if (Addr[3] == 1'b1)
$display (" Burst Type = Interleaved");
else
$display (" Burst Type = Reserved");
// Write Burst Mode
if (Addr[9] == 1'b0)
$display (" Write Burst Mode = Programmed Burst Length");
else if (Addr[9] == 1'b1)
$display (" Write Burst Mode = Single Location Access");
else
$display (" Write Burst Mode = Reserved");
end
end else begin
$display ("at time %t ERROR: all banks must be Precharge before Load Mode Register", $time);
end
// REF to LMR
if ($time - RC_chk < tRC) begin
$display ("at time %t ERROR: tRC violation during Load Mode Register", $time);
end
// LMR to LMR
if (MRD_chk < tMRD) begin
$display ("at time %t ERROR: tMRD violation during Load Mode Register", $time);
end
MRD_chk = 0;
end
// Active Block (Latch Bank Address and Row Address)
if (Active_enable == 1'b1) begin
if (Ba == 2'b00 && Pc_b0 == 1'b1) begin
{Act_b0, Pc_b0} = 2'b10;
B0_row_addr = Addr [addr_bits - 1 : 0];
RCD_chk0 = $time;
RAS_chk0 = $time;
if (Debug) $display ("at time %t ACT : Bank = 0 Row = %d", $time, Addr);
// Precharge to Activate Bank 0
if ($time - RP_chk0 < tRP) begin
$display ("at time %t ERROR: tRP violation during Activate bank 0", $time);
end
end else if (Ba == 2'b01 && Pc_b1 == 1'b1) begin
{Act_b1, Pc_b1} = 2'b10;
B1_row_addr = Addr [addr_bits - 1 : 0];
RCD_chk1 = $time;
RAS_chk1 = $time;
if (Debug) $display ("at time %t ACT : Bank = 1 Row = %d", $time, Addr);
// Precharge to Activate Bank 1
if ($time - RP_chk1 < tRP) begin
$display ("at time %t ERROR: tRP violation during Activate bank 1", $time);
end
end else if (Ba == 2'b10 && Pc_b2 == 1'b1) begin
{Act_b2, Pc_b2} = 2'b10;
B2_row_addr = Addr [addr_bits - 1 : 0];
RCD_chk2 = $time;
RAS_chk2 = $time;
if (Debug) $display ("at time %t ACT : Bank = 2 Row = %d", $time, Addr);
// Precharge to Activate Bank 2
if ($time - RP_chk2 < tRP) begin
$display ("at time %t ERROR: tRP violation during Activate bank 2", $time);
end
end else if (Ba == 2'b11 && Pc_b3 == 1'b1) begin
{Act_b3, Pc_b3} = 2'b10;
B3_row_addr = Addr [addr_bits - 1 : 0];
RCD_chk3 = $time;
RAS_chk3 = $time;
if (Debug) $display ("at time %t ACT : Bank = 3 Row = %d", $time, Addr);
// Precharge to Activate Bank 3
if ($time - RP_chk3 < tRP) begin
$display ("at time %t ERROR: tRP violation during Activate bank 3", $time);
end
end else if (Ba == 2'b00 && Pc_b0 == 1'b0) begin
$display ("at time %t ERROR: Bank 0 is not Precharged.", $time);
end else if (Ba == 2'b01 && Pc_b1 == 1'b0) begin
$display ("at time %t ERROR: Bank 1 is not Precharged.", $time);
end else if (Ba == 2'b10 && Pc_b2 == 1'b0) begin
$display ("at time %t ERROR: Bank 2 is not Precharged.", $time);
end else if (Ba == 2'b11 && Pc_b3 == 1'b0) begin
$display ("at time %t ERROR: Bank 3 is not Precharged.", $time);
end
// Active Bank A to Active Bank B
if ((Previous_bank != Ba) && ($time - RRD_chk < tRRD)) begin
$display ("at time %t ERROR: tRRD violation during Activate bank = %d", $time, Ba);
end
// Load Mode Register to Active
if (MRD_chk < tMRD ) begin
$display ("at time %t ERROR: tMRD violation during Activate bank = %d", $time, Ba);
end
// Auto Refresh to Activate
if (($time - RC_chk < tRC)&&Debug) begin
$display ("at time %t ERROR: tRC violation during Activate bank = %d", $time, Ba);
end
// Record variables for checking violation
RRD_chk = $time;
Previous_bank = Ba;
end
// Precharge Block
if (Prech_enable == 1'b1) begin
if (Addr[10] == 1'b1) begin
{Pc_b0, Pc_b1, Pc_b2, Pc_b3} = 4'b1111;
{Act_b0, Act_b1, Act_b2, Act_b3} = 4'b0000;
RP_chk0 = $time;
RP_chk1 = $time;
RP_chk2 = $time;
RP_chk3 = $time;
if (Debug) $display ("at time %t PRE : Bank = ALL",$time);
// Activate to Precharge all banks
if (($time - RAS_chk0 < tRAS) || ($time - RAS_chk1 < tRAS) ||
($time - RAS_chk2 < tRAS) || ($time - RAS_chk3 < tRAS)) begin
$display ("at time %t ERROR: tRAS violation during Precharge all bank", $time);
end
// tWR violation check for write
if (($time - WR_chk[0] < tWRp) || ($time - WR_chk[1] < tWRp) ||
($time - WR_chk[2] < tWRp) || ($time - WR_chk[3] < tWRp)) begin
$display ("at time %t ERROR: tWR violation during Precharge all bank", $time);
end
end else if (Addr[10] == 1'b0) begin
if (Ba == 2'b00) begin
{Pc_b0, Act_b0} = 2'b10;
RP_chk0 = $time;
if (Debug) $display ("at time %t PRE : Bank = 0",$time);
// Activate to Precharge Bank 0
if ($time - RAS_chk0 < tRAS) begin
$display ("at time %t ERROR: tRAS violation during Precharge bank 0", $time);
end
end else if (Ba == 2'b01) begin
{Pc_b1, Act_b1} = 2'b10;
RP_chk1 = $time;
if (Debug) $display ("at time %t PRE : Bank = 1",$time);
// Activate to Precharge Bank 1
if ($time - RAS_chk1 < tRAS) begin
$display ("at time %t ERROR: tRAS violation during Precharge bank 1", $time);
end
end else if (Ba == 2'b10) begin
{Pc_b2, Act_b2} = 2'b10;
RP_chk2 = $time;
if (Debug) $display ("at time %t PRE : Bank = 2",$time);
// Activate to Precharge Bank 2
if ($time - RAS_chk2 < tRAS) begin
$display ("at time %t ERROR: tRAS violation during Precharge bank 2", $time);
end
end else if (Ba == 2'b11) begin
{Pc_b3, Act_b3} = 2'b10;
RP_chk3 = $time;
if (Debug) $display ("at time %t PRE : Bank = 3",$time);
// Activate to Precharge Bank 3
if ($time - RAS_chk3 < tRAS) begin
$display ("at time %t ERROR: tRAS violation during Precharge bank 3", $time);
end
end
// tWR violation check for write
if ($time - WR_chk[Ba] < tWRp) begin
$display ("at time %t ERROR: tWR violation during Precharge bank %d", $time, Ba);
end
end
// Terminate a Write Immediately (if same bank or all banks)
if (Data_in_enable == 1'b1 && (Bank == Ba || Addr[10] == 1'b1)) begin
Data_in_enable = 1'b0;
end
// Precharge Command Pipeline for Read
if (Cas_latency_3 == 1'b1) begin
Command[2] = `PRECH;
Bank_precharge[2] = Ba;
A10_precharge[2] = Addr[10];
end else if (Cas_latency_2 == 1'b1) begin
Command[1] = `PRECH;
Bank_precharge[1] = Ba;
A10_precharge[1] = Addr[10];
end
end
// Burst terminate
if (Burst_term == 1'b1) begin
// Terminate a Write Immediately
if (Data_in_enable == 1'b1) begin
Data_in_enable = 1'b0;
end
// Terminate a Read Depend on CAS Latency
if (Cas_latency_3 == 1'b1) begin
Command[2] = `BST;
end else if (Cas_latency_2 == 1'b1) begin
Command[1] = `BST;
end
if (Debug) $display ("at time %t BST : Burst Terminate",$time);
end
// Read, Write, Column Latch
if (Read_enable == 1'b1 || Write_enable == 1'b1) begin
// Check to see if bank is open (ACT)
if ((Ba == 2'b00 && Pc_b0 == 1'b1) || (Ba == 2'b01 && Pc_b1 == 1'b1) ||
(Ba == 2'b10 && Pc_b2 == 1'b1) || (Ba == 2'b11 && Pc_b3 == 1'b1)) begin
$display("at time %t ERROR: Cannot Read or Write - Bank %d is not Activated", $time, Ba);
end
// Activate to Read or Write
if ((Ba == 2'b00) && ($time - RCD_chk0 < tRCD))
$display("at time %t ERROR: tRCD violation during Read or Write to Bank 0", $time);
if ((Ba == 2'b01) && ($time - RCD_chk1 < tRCD))
$display("at time %t ERROR: tRCD violation during Read or Write to Bank 1", $time);
if ((Ba == 2'b10) && ($time - RCD_chk2 < tRCD))
$display("at time %t ERROR: tRCD violation during Read or Write to Bank 2", $time);
if ((Ba == 2'b11) && ($time - RCD_chk3 < tRCD))
$display("at time %t ERROR: tRCD violation during Read or Write to Bank 3", $time);
// Read Command
if (Read_enable == 1'b1) begin
// CAS Latency pipeline
if (Cas_latency_3 == 1'b1) begin
if (Addr[10] == 1'b1) begin
Command[2] = `READ_A;
end else begin
Command[2] = `READ;
end
Col_addr[2] = Addr;
Bank_addr[2] = Ba;
end else if (Cas_latency_2 == 1'b1) begin
if (Addr[10] == 1'b1) begin
Command[1] = `READ_A;
end else begin
Command[1] = `READ;
end
Col_addr[1] = Addr;
Bank_addr[1] = Ba;
end
// Read interrupt Write (terminate Write immediately)
if (Data_in_enable == 1'b1) begin
Data_in_enable = 1'b0;
end
// Write Command
end else if (Write_enable == 1'b1) begin
if (Addr[10] == 1'b1) begin
Command[0] = `WRITE_A;
end else begin
Command[0] = `WRITE;
end
Col_addr[0] = Addr;
Bank_addr[0] = Ba;
// Write interrupt Write (terminate Write immediately)
if (Data_in_enable == 1'b1) begin
Data_in_enable = 1'b0;
end
// Write interrupt Read (terminate Read immediately)
if (Data_out_enable == 1'b1) begin
Data_out_enable = 1'b0;
end
end
// Interrupting a Write with Autoprecharge
if (Auto_precharge[Bank] == 1'b1 && Write_precharge[Bank] == 1'b1) begin
RW_interrupt_write[Bank] = 1'b1;
if (Debug) $display ("at time %t NOTE : Read/Write Bank %d interrupt Write Bank %d with Autoprecharge", $time, Ba, Bank);
end
// Interrupting a Read with Autoprecharge
if (Auto_precharge[Bank] == 1'b1 && Read_precharge[Bank] == 1'b1) begin
RW_interrupt_read[Bank] = 1'b1;
if (Debug) $display ("at time %t NOTE : Read/Write Bank %d interrupt Read Bank %d with Autoprecharge", $time, Ba, Bank);
end
// Read or Write with Auto Precharge
if (Addr[10] == 1'b1) begin
Auto_precharge[Ba] = 1'b1;
Count_precharge[Ba] = 0;
if (Read_enable == 1'b1) begin
Read_precharge[Ba] = 1'b1;
end else if (Write_enable == 1'b1) begin
Write_precharge[Ba] = 1'b1;
end
end
end
// Read with Auto Precharge Calculation
// The device start internal precharge:
// 1. CAS Latency - 1 cycles before last burst
// and 2. Meet minimum tRAS requirement
// or 3. Interrupt by a Read or Write (with or without AutoPrecharge)
if ((Auto_precharge[0] == 1'b1) && (Read_precharge[0] == 1'b1)) begin
if ((($time - RAS_chk0 >= tRAS) && // Case 2
((Burst_length_1 == 1'b1 && Count_precharge[0] >= 1) || // Case 1
(Burst_length_2 == 1'b1 && Count_precharge[0] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge[0] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge[0] >= 8))) ||
(RW_interrupt_read[0] == 1'b1)) begin // Case 3
Pc_b0 = 1'b1;
Act_b0 = 1'b0;
RP_chk0 = $time;
Auto_precharge[0] = 1'b0;
Read_precharge[0] = 1'b0;
RW_interrupt_read[0] = 1'b0;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 0", $time);
end
end
if ((Auto_precharge[1] == 1'b1) && (Read_precharge[1] == 1'b1)) begin
if ((($time - RAS_chk1 >= tRAS) &&
((Burst_length_1 == 1'b1 && Count_precharge[1] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge[1] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge[1] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge[1] >= 8))) ||
(RW_interrupt_read[1] == 1'b1)) begin
Pc_b1 = 1'b1;
Act_b1 = 1'b0;
RP_chk1 = $time;
Auto_precharge[1] = 1'b0;
Read_precharge[1] = 1'b0;
RW_interrupt_read[1] = 1'b0;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 1", $time);
end
end
if ((Auto_precharge[2] == 1'b1) && (Read_precharge[2] == 1'b1)) begin
if ((($time - RAS_chk2 >= tRAS) &&
((Burst_length_1 == 1'b1 && Count_precharge[2] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge[2] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge[2] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge[2] >= 8))) ||
(RW_interrupt_read[2] == 1'b1)) begin
Pc_b2 = 1'b1;
Act_b2 = 1'b0;
RP_chk2 = $time;
Auto_precharge[2] = 1'b0;
Read_precharge[2] = 1'b0;
RW_interrupt_read[2] = 1'b0;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 2", $time);
end
end
if ((Auto_precharge[3] == 1'b1) && (Read_precharge[3] == 1'b1)) begin
if ((($time - RAS_chk3 >= tRAS) &&
((Burst_length_1 == 1'b1 && Count_precharge[3] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge[3] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge[3] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge[3] >= 8))) ||
(RW_interrupt_read[3] == 1'b1)) begin
Pc_b3 = 1'b1;
Act_b3 = 1'b0;
RP_chk3 = $time;
Auto_precharge[3] = 1'b0;
Read_precharge[3] = 1'b0;
RW_interrupt_read[3] = 1'b0;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 3", $time);
end
end
// Internal Precharge or Bst
if (Command[0] == `PRECH) begin // Precharge terminate a read with same bank or all banks
if (Bank_precharge[0] == Bank || A10_precharge[0] == 1'b1) begin
if (Data_out_enable == 1'b1) begin
Data_out_enable = 1'b0;
end
end
end else if (Command[0] == `BST) begin // BST terminate a read to current bank
if (Data_out_enable == 1'b1) begin
Data_out_enable = 1'b0;
end
end
if (Data_out_enable == 1'b0) begin
Dq_reg <= #tOH {data_bits{1'bz}};
end
// Detect Read or Write command
if (Command[0] == `READ || Command[0] == `READ_A) begin
Bank = Bank_addr[0];
Col = Col_addr[0];
Col_brst = Col_addr[0];
if (Bank_addr[0] == 2'b00) begin
Row = B0_row_addr;
end else if (Bank_addr[0] == 2'b01) begin
Row = B1_row_addr;
end else if (Bank_addr[0] == 2'b10) begin
Row = B2_row_addr;
end else if (Bank_addr[0] == 2'b11) begin
Row = B3_row_addr;
end
Burst_counter = 0;
Data_in_enable = 1'b0;
Data_out_enable = 1'b1;
end else if (Command[0] == `WRITE || Command[0] == `WRITE_A) begin
Bank = Bank_addr[0];
Col = Col_addr[0];
Col_brst = Col_addr[0];
if (Bank_addr[0] == 2'b00) begin
Row = B0_row_addr;
end else if (Bank_addr[0] == 2'b01) begin
Row = B1_row_addr;
end else if (Bank_addr[0] == 2'b10) begin
Row = B2_row_addr;
end else if (Bank_addr[0] == 2'b11) begin
Row = B3_row_addr;
end
Burst_counter = 0;
Data_in_enable = 1'b1;
Data_out_enable = 1'b0;
end
// DQ buffer (Driver/Receiver)
if (Data_in_enable == 1'b1) begin // Writing Data to Memory
// Array buffer
if (Bank == 2'b00) Dq_dqm [data_bits - 1 : 0] = Bank0 [{Row, Col}];
if (Bank == 2'b01) Dq_dqm [data_bits - 1 : 0] = Bank1 [{Row, Col}];
if (Bank == 2'b10) Dq_dqm [data_bits - 1 : 0] = Bank2 [{Row, Col}];
if (Bank == 2'b11) Dq_dqm [data_bits - 1 : 0] = Bank3 [{Row, Col}];
// Dqm operation
if (Dqm[0] == 1'b0) Dq_dqm [ 7 : 0] = Dq [ 7 : 0];
if (Dqm[1] == 1'b0) Dq_dqm [15 : 8] = Dq [15 : 8];
//if (Dqm[2] == 1'b0) Dq_dqm [23 : 16] = Dq [23 : 16];
// if (Dqm[3] == 1'b0) Dq_dqm [31 : 24] = Dq [31 : 24];
// Write to memory
if (Bank == 2'b00) Bank0 [{Row, Col}] = Dq_dqm [data_bits - 1 : 0];
if (Bank == 2'b01) Bank1 [{Row, Col}] = Dq_dqm [data_bits - 1 : 0];
if (Bank == 2'b10) Bank2 [{Row, Col}] = Dq_dqm [data_bits - 1 : 0];
if (Bank == 2'b11) Bank3 [{Row, Col}] = Dq_dqm [data_bits - 1 : 0];
if (Bank == 2'b11 && Row==10'h3 && Col[7:4]==4'h4)
$display("at time %t WRITE: Bank = %d Row = %d, Col = %d, Data = Hi-Z due to DQM", $time, Bank, Row, Col);
//$fdisplay(test_file,"bank:%h row:%h col:%h write:%h",Bank,Row,Col,Dq_dqm);
// Output result
if (Dqm == 4'b1111) begin
if (Debug) $display("at time %t WRITE: Bank = %d Row = %d, Col = %d, Data = Hi-Z due to DQM", $time, Bank, Row, Col);
end else begin
if (Debug) $display("at time %t WRITE: Bank = %d Row = %d, Col = %d, Data = %d, Dqm = %b", $time, Bank, Row, Col, Dq_dqm, Dqm);
// Record tWR time and reset counter
WR_chk [Bank] = $time;
WR_counter [Bank] = 0;
end
// Advance burst counter subroutine
#tHZ Burst;
end else if (Data_out_enable == 1'b1) begin // Reading Data from Memory
//$display("%h , %h, %h",Bank0,Row,Col);
// Array buffer
if (Bank == 2'b00) Dq_dqm [data_bits - 1 : 0] = Bank0 [{Row, Col}];
if (Bank == 2'b01) Dq_dqm [data_bits - 1 : 0] = Bank1 [{Row, Col}];
if (Bank == 2'b10) Dq_dqm [data_bits - 1 : 0] = Bank2 [{Row, Col}];
if (Bank == 2'b11) Dq_dqm [data_bits - 1 : 0] = Bank3 [{Row, Col}];
// Dqm operation
if (Dqm_reg0[0] == 1'b1) Dq_dqm [ 7 : 0] = 8'bz;
if (Dqm_reg0[1] == 1'b1) Dq_dqm [15 : 8] = 8'bz;
if (Dqm_reg0[2] == 1'b1) Dq_dqm [23 : 16] = 8'bz;
if (Dqm_reg0[3] == 1'b1) Dq_dqm [31 : 24] = 8'bz;
// Display result
Dq_reg [data_bits - 1 : 0] = #tAC Dq_dqm [data_bits - 1 : 0];
if (Dqm_reg0 == 4'b1111) begin
if (Debug) $display("at time %t READ : Bank = %d Row = %d, Col = %d, Data = Hi-Z due to DQM", $time, Bank, Row, Col);
end else begin
if (Debug) $display("at time %t READ : Bank = %d Row = %d, Col = %d, Data = %d, Dqm = %b", $time, Bank, Row, Col, Dq_reg, Dqm_reg0);
end
// Advance burst counter subroutine
Burst;
end
end
// Write with Auto Precharge Calculation
// The device start internal precharge:
// 1. tWR Clock after last burst
// and 2. Meet minimum tRAS requirement
// or 3. Interrupt by a Read or Write (with or without AutoPrecharge)
always @ (WR_counter[0]) begin
if ((Auto_precharge[0] == 1'b1) && (Write_precharge[0] == 1'b1)) begin
if ((($time - RAS_chk0 >= tRAS) && // Case 2
(((Burst_length_1 == 1'b1 || Write_burst_mode == 1'b1) && Count_precharge [0] >= 1) || // Case 1
(Burst_length_2 == 1'b1 && Count_precharge [0] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge [0] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge [0] >= 8))) ||
(RW_interrupt_write[0] == 1'b1 && WR_counter[0] >= 2)) begin // Case 3 (stop count when interrupt)
Auto_precharge[0] = 1'b0;
Write_precharge[0] = 1'b0;
RW_interrupt_write[0] = 1'b0;
#tWRa; // Wait for tWR
Pc_b0 = 1'b1;
Act_b0 = 1'b0;
RP_chk0 = $time;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 0", $time);
end
end
end
always @ (WR_counter[1]) begin
if ((Auto_precharge[1] == 1'b1) && (Write_precharge[1] == 1'b1)) begin
if ((($time - RAS_chk1 >= tRAS) &&
(((Burst_length_1 == 1'b1 || Write_burst_mode == 1'b1) && Count_precharge [1] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge [1] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge [1] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge [1] >= 8))) ||
(RW_interrupt_write[1] == 1'b1 && WR_counter[1] >= 2)) begin
Auto_precharge[1] = 1'b0;
Write_precharge[1] = 1'b0;
RW_interrupt_write[1] = 1'b0;
#tWRa; // Wait for tWR
Pc_b1 = 1'b1;
Act_b1 = 1'b0;
RP_chk1 = $time;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 1", $time);
end
end
end
always @ (WR_counter[2]) begin
if ((Auto_precharge[2] == 1'b1) && (Write_precharge[2] == 1'b1)) begin
if ((($time - RAS_chk2 >= tRAS) &&
(((Burst_length_1 == 1'b1 || Write_burst_mode == 1'b1) && Count_precharge [2] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge [2] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge [2] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge [2] >= 8))) ||
(RW_interrupt_write[2] == 1'b1 && WR_counter[2] >= 2)) begin
Auto_precharge[2] = 1'b0;
Write_precharge[2] = 1'b0;
RW_interrupt_write[2] = 1'b0;
#tWRa; // Wait for tWR
Pc_b2 = 1'b1;
Act_b2 = 1'b0;
RP_chk2 = $time;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 2", $time);
end
end
end
always @ (WR_counter[3]) begin
if ((Auto_precharge[3] == 1'b1) && (Write_precharge[3] == 1'b1)) begin
if ((($time - RAS_chk3 >= tRAS) &&
(((Burst_length_1 == 1'b1 || Write_burst_mode == 1'b1) && Count_precharge [3] >= 1) ||
(Burst_length_2 == 1'b1 && Count_precharge [3] >= 2) ||
(Burst_length_4 == 1'b1 && Count_precharge [3] >= 4) ||
(Burst_length_8 == 1'b1 && Count_precharge [3] >= 8))) ||
(RW_interrupt_write[3] == 1'b1 && WR_counter[3] >= 2)) begin
Auto_precharge[3] = 1'b0;
Write_precharge[3] = 1'b0;
RW_interrupt_write[3] = 1'b0;
#tWRa; // Wait for tWR
Pc_b3 = 1'b1;
Act_b3 = 1'b0;
RP_chk3 = $time;
if (Debug) $display ("at time %t NOTE : Start Internal Auto Precharge for Bank 3", $time);
end
end
end
task Burst;
begin
// Advance Burst Counter
Burst_counter = Burst_counter + 1;
// Burst Type
if (Mode_reg[3] == 1'b0) begin // Sequential Burst
Col_temp = Col + 1;
end else if (Mode_reg[3] == 1'b1) begin // Interleaved Burst
Col_temp[2] = Burst_counter[2] ^ Col_brst[2];
Col_temp[1] = Burst_counter[1] ^ Col_brst[1];
Col_temp[0] = Burst_counter[0] ^ Col_brst[0];
end
// Burst Length
if (Burst_length_2) begin // Burst Length = 2
Col [0] = Col_temp [0];
end else if (Burst_length_4) begin // Burst Length = 4
Col [1 : 0] = Col_temp [1 : 0];
end else if (Burst_length_8) begin // Burst Length = 8
Col [2 : 0] = Col_temp [2 : 0];
end else begin // Burst Length = FULL
Col = Col_temp;
end
// Burst Read Single Write
if (Write_burst_mode == 1'b1) begin
Data_in_enable = 1'b0;
end
// Data Counter
if (Burst_length_1 == 1'b1) begin
if (Burst_counter >= 1) begin
Data_in_enable = 1'b0;
Data_out_enable = 1'b0;
end
end else if (Burst_length_2 == 1'b1) begin
if (Burst_counter >= 2) begin
Data_in_enable = 1'b0;
Data_out_enable = 1'b0;
end
end else if (Burst_length_4 == 1'b1) begin
if (Burst_counter >= 4) begin
Data_in_enable = 1'b0;
Data_out_enable = 1'b0;
end
end else if (Burst_length_8 == 1'b1) begin
if (Burst_counter >= 8) begin
Data_in_enable = 1'b0;
Data_out_enable = 1'b0;
end
end
end
endtask
//**********************将SDRAM内的数据直接输出到外部文件*******************************//
/*
integer sdram_data,ind;
always@(sdram_r)
begin
sdram_data=$fopen("sdram_data.txt");
$display("Sdram dampout begin ",sdram_data);
// $fdisplay(sdram_data,"Bank0：");
for(ind=0;ind<=mem_sizes;ind=ind+1)
$fdisplay(sdram_data,"%h %b",ind,Bank0[ind]);
// $fdisplay(sdram_data,"Bank1：");
for(ind=0;ind<=mem_sizes;ind=ind+1)
$fdisplay(sdram_data,"%h %b",ind,Bank1[ind]);
// $fdisplay(sdram_data,"Bank2：");
for(ind=0;ind<=mem_sizes;ind=ind+1)
$fdisplay(sdram_data,"%h %b",ind,Bank2[ind]);
// $fdisplay(sdram_data,"Bank3：");
for(ind=0;ind<=mem_sizes;ind=ind+1)
$fdisplay(sdram_data,"%h %b",ind,Bank3[ind]);
$fclose("sdram_data.txt");
//->compare;
end
*/
integer sdram_data,sdram_mem;
reg [23:0] aa,cc;
reg [18:0] bb,ee;
always@(sdram_r)
begin
$display("Sdram dampout begin ",$realtime);
sdram_data=$fopen("sdram_data.txt");
for(aa=0;aa<4*(mem_sizes+1);aa=aa+1)
begin
bb=aa[18:0];
if(aa<=mem_sizes)
$fdisplay(sdram_data,"%0d %0h",aa,Bank0[bb]);
else if(aa<=2*mem_sizes+1)
$fdisplay(sdram_data,"%0d %0h",aa,Bank1[bb]);
else if(aa<=3*mem_sizes+2)
$fdisplay(sdram_data,"%0d %0h",aa,Bank2[bb]);
else
$fdisplay(sdram_data,"%0d %0h",aa,Bank3[bb]);
end
$fclose("sdram_data.txt");
sdram_mem=$fopen("sdram_mem.txt");
for(cc=0;cc<4*(mem_sizes+1);cc=cc+1)
begin
ee=cc[18:0];
if(cc<=mem_sizes)
$fdisplay(sdram_mem,"%0h",Bank0[ee]);
else if(cc<=2*mem_sizes+1)
$fdisplay(sdram_mem,"%0h",Bank1[ee]);
else if(cc<=3*mem_sizes+2)
$fdisplay(sdram_mem,"%0h",Bank2[ee]);
else
$fdisplay(sdram_mem,"%0h",Bank3[ee]);
end
$fclose("sdram_mem.txt");
end
// // Timing Parameters for -75 (PC133) and CAS Latency = 2
// specify
// specparam
//// tAH = 0.8, // Addr, Ba Hold Time
//// tAS = 1.5, // Addr, Ba Setup Time
//// tCH = 2.5, // Clock High-Level Width
//// tCL = 2.5, // Clock Low-Level Width
////// tCK = 10.0, // Clock Cycle Time 100mhz
////// tCK = 7.5, // Clock Cycle Time 133mhz
//// tCK = 7, // Clock Cycle Time 143mhz
//// tDH = 0.8, // Data-in Hold Time
//// tDS = 1.5, // Data-in Setup Time
//// tCKH = 0.8, // CKE Hold Time
//// tCKS = 1.5, // CKE Setup Time
//// tCMH = 0.8, // CS#, RAS#, CAS#, WE#, DQM# Hold Time
//// tCMS = 1.5; // CS#, RAS#, CAS#, WE#, DQM# Setup Time
// tAH = 1, // Addr, Ba Hold Time
// tAS = 1.5, // Addr, Ba Setup Time
// tCH = 1, // Clock High-Level Width
// tCL = 3, // Clock Low-Level Width
//// tCK = 10.0, // Clock Cycle Time 100mhz
//// tCK = 7.5, // Clock Cycle Time 133mhz
// tCK = 7, // Clock Cycle Time 143mhz
// tDH = 1, // Data-in Hold Time
// tDS = 2, // Data-in Setup Time
// tCKH = 1, // CKE Hold Time
// tCKS = 2, // CKE Setup Time
// tCMH = 0.8, // CS#, RAS#, CAS#, WE#, DQM# Hold Time
// tCMS = 1.5; // CS#, RAS#, CAS#, WE#, DQM# Setup Time
// $width (posedge Clk, tCH);
// $width (negedge Clk, tCL);
// $period (negedge Clk, tCK);
// $period (posedge Clk, tCK);
// $setuphold(posedge Clk, Cke, tCKS, tCKH);
// $setuphold(posedge Clk, Cs_n, tCMS, tCMH);
// $setuphold(posedge Clk, Cas_n, tCMS, tCMH);
// $setuphold(posedge Clk, Ras_n, tCMS, tCMH);
// $setuphold(posedge Clk, We_n, tCMS, tCMH);
// $setuphold(posedge Clk, Addr, tAS, tAH);
// $setuphold(posedge Clk, Ba, tAS, tAH);
// $setuphold(posedge Clk, Dqm, tCMS, tCMH);
// $setuphold(posedge Dq_chk, Dq, tDS, tDH);
// endspecify
endmodule
该模块是官方提供的，大家不需要太在意，就把该模块想想成一块SDRAM就可以了，该模块里面的数据可以根据具体的SDRAM型号进行配置，这点在顶层测试代码中已经给出重配置的方式。
仿真结果测试
仿真结果如下：
这里Kevin老师说自刷新模块之前不需要预充电命令，因为读写命令的之前都有自刷新命令，但是如果SDRAM既不执行读操作也不执行写操作的情况下，等待15us，那么自刷新命令之前就没有预充电命令，所以
我认为自刷新模块还是需要预充电命令的。
参考文献
[1]、开源骚客
总结
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