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本文相对简单，只供自己看看就行。从其它的博客找了个代码，然后记录下仿真波形。
1. 功能
直接使用quartus生成的DDR2 IP核，然后实现循环 -->写入burst长度的数据后读出。
代码数据的传输是32位，实际使用了两片IC。因此IP核也是32位交互。
2.信号分析
burst=4，是IC固有的=预取值。而代码中LEN为用户一次想要读取数据的长度的。与local_size和burst_length无关。
分为4个状态: IDLE、WRITER、WRITING、READR、READING。WRITER和READR状态下，开始读写burst的第一个数据，其余的在WRITING和READING状态读写。
local_ready：很重要的一个指示信号。要进行读写操作，必须在IP核（ddr2）准备好的情况下进行。因此，需要一直对此信号进行检测判断。
写入地址（mem_local_addr），一开始为1，当读到的数据长度rdatalen=5时（初始值=1），mem_local_addr <= mem_local_addr + 4；
命令
连续写
连续读
读完写
3. 仿真波形分析
如下图所示：每次先写入连续4个数据，（例如1，2，3，4），然后再依次读出。
读过程及下一次写
4. 附代码
顶层代码：
module ddr2wrtest (input clk , // Clockinput global_reset_n , // Asynchronous reset active lowoutput [ 12: 0] mem_addr , output [ 2: 0] mem_ba , output mem_cas_n , output mem_cke , inout mem_clk , inout mem_clk_n , output mem_cs_n , output [ 1: 0] mem_dm , inout [ 15: 0] mem_dq , inout [ 1: 0] mem_dqs , output mem_odt , output mem_ras_n , output mem_we_n );parameter LEN = 8; // 突发长度 4parameter IDEL = 5'b00001; // 空闲态parameter WRITER = 5'b00010; // 准备写parameter WRITING = 5'b00100; // 写状态parameter READR = 5'b01000; // 准备读parameter READING = 5'b10000; // 读状态reg [ 5: 0] state;
//**********************与IP相连部分********************//reg [ 24: 0] mem_local_addr =1 ;wire mem_local_init_done ; wire local_burstbegin_sig ; wire [ 31: 0] mem_local_rdata ;wire mem_local_rdata_valid ;wire mem_local_read_req ;wire mem_local_ready ; wire [ 3: 0] mem_local_size ;reg [ 31: 0] mem_local_wdata ;wire mem_local_write_req ;wire phy_clk ;wire reset_phy_clk_n ;
//*****************************************************//wire rst_n ;reg [ 3: 0] rdatalen ; // 读突发长度计数器reg [ 3: 0] wdatalen ; // 写突发长度计数器reg [100: 0] state_name ; // 状态名assign rst_n = reset_phy_clk_n&&mem_local_init_done;assign mem_local_size = LEN;assign local_burstbegin_sig = ((state == WRITER&&mem_local_ready) || (state == READR&&mem_local_ready))?1:0;assign mem_local_write_req = (state == WRITING)?1:0;assign mem_local_read_req = (state == READR&&mem_local_ready)?1:0;ddr2 ddr2_inst(
//==============================《 》===============================.aux_full_rate_clk ( ), //全速率时钟.aux_half_rate_clk ( ), //半速率时钟
//==============================《 用户操作信号 》===============================.global_reset_n (global_reset_n ), //全局复位.local_address (mem_local_addr ), //当前操作地址.local_be (8'hff ), //数据掩码.local_burstbegin (local_burstbegin_sig ), //突发起始信号.local_init_done (mem_local_init_done ), //初始化完成信号.local_rdata (mem_local_rdata ), //读数据总线.local_rdata_valid (mem_local_rdata_valid ), //读有效标志.local_read_req (mem_local_read_req ), //读请求，保持一个时钟周期.local_ready (mem_local_ready ), //接受到请求.local_refresh_ack ( ), //自动刷新.local_size (mem_local_size ), //突发长度.local_wdata (mem_local_wdata ), //写数据总线.local_write_req (mem_local_write_req ), //写请求
//==============================《 与DDR2相连的信号 》===============================.mem_addr (mem_addr ), //地址总线.mem_ba (mem_ba ), //bank地址.mem_cas_n (mem_cas_n ), //行选通.mem_cke (mem_cke ), //时钟使能.mem_clk (mem_clk ), //操作时钟.mem_clk_n (mem_clk_n ), //反向时钟.mem_cs_n (mem_cs_n ), //片选信号.mem_dm (mem_dm ), //DDR2数据屏蔽信号.mem_dq (mem_dq ), //数据总线.mem_dqs (mem_dqs ), //数据选取脉冲信号.mem_odt (mem_odt ), //片内终结信号.mem_ras_n (mem_ras_n ), //行选通.mem_we_n (mem_we_n ), //使能
//==============================《 用户操作信号 》===============================.phy_clk (phy_clk ), //提供给用户的操作时钟.pll_ref_clk (clk ), //给ddr2的输入时钟.reset_phy_clk_n (reset_phy_clk_n ), //提供给用户的复位信号.reset_request_n ( ), //当PLL锁定后为低电平.soft_reset_n (1'b1 ) //软复位，不包括PLL的复位);always@(*)case (state)IDEL : state_name = "IDEL";WRITER : state_name = "WRITER" ; WRITING : state_name = "WRITING" ; READR : state_name = "READR" ; READING : state_name = "READING";default : /* default */;endcasealways@(posedge phy_clk or negedge rst_n)begin if(!rst_n)state <= IDEL;elsecase (state)IDEL : state <= WRITER;WRITER : if(mem_local_ready)state <= WRITING;elsestate <= WRITER;WRITING : if(wdatalen == LEN)state <= READR;elsestate <= state;READR : if(mem_local_ready)state <= READING;elsestate <= READR;READING : if(rdatalen == LEN)state <= IDEL;elsestate <= state; default : state <= state;endcaseend// 写的数据自加1always@(posedge phy_clk or negedge rst_n)begin if(!rst_n)mem_local_wdata <= 1;else if(state == WRITING && mem_local_ready)mem_local_wdata <= mem_local_wdata + 1;elsemem_local_wdata <= mem_local_wdata;end// 当前写的数据突发长度always@(posedge phy_clk or negedge rst_n)begin if(!rst_n) wdatalen <= 1;else if(state == WRITING && mem_local_ready)wdatalen <= wdatalen + 1;else if(state == WRITING && !mem_local_ready)wdatalen <= wdatalen ;elsewdatalen <= 1;end// 当前读的数据突发长度always@(posedge phy_clk or negedge rst_n)begin if(!rst_n) rdatalen <= 1;else if(state == READING && mem_local_rdata_valid)rdatalen <= rdatalen + 1;elserdatalen <= 1;end// 操作地址自加always@(posedge phy_clk or negedge rst_n)begin if(!rst_n)mem_local_addr <= 1;else if(rdatalen == LEN)mem_local_addr <= mem_local_addr + LEN;endendmodule
测试代码
`timescale 1ns/1ps
module test_tb ();reg clk ;
reg global_reset_n;wire [ 12: 0] mem_addr ;
wire [ 2: 0] mem_ba ;
wire mem_cas_n ;
wire mem_cke ;
wire mem_clk ;
wire mem_clk_n ;
wire mem_cs_n ;
wire [ 1: 0] mem_dm ;
wire [ 15: 0] mem_dq ;
wire [ 1: 0] mem_dqs ;
wire mem_odt ;
wire mem_ras_n ;
wire mem_we_n ;ddr2wrtest u1 (.clk (clk ), // Clock.global_reset_n (global_reset_n ) , // Asynchronous reset active low.mem_addr (mem_addr ), .mem_ba (mem_ba ), .mem_cas_n (mem_cas_n ), .mem_cke (mem_cke ), .mem_clk (mem_clk ), .mem_clk_n (mem_clk_n ), .mem_cs_n (mem_cs_n ), .mem_dm (mem_dm ), .mem_dq (mem_dq ), .mem_dqs (mem_dqs ), .mem_odt (mem_odt ), .mem_ras_n (mem_ras_n ), .mem_we_n (mem_we_n ) );ddr2_mem_model mem (.mem_dq (mem_dq),.mem_dqs (mem_dqs),.mem_dqs_n (mem_dqs_n),.mem_addr (mem_addr),.mem_ba (mem_ba),.mem_clk (mem_clk),.mem_clk_n (mem_clk_n),.mem_cke (mem_cke),.mem_cs_n (mem_cs_n),.mem_ras_n (mem_ras_n),.mem_cas_n (mem_cas_n),.mem_we_n (mem_we_n),.mem_dm (mem_dm),.mem_odt (mem_odt));
always #10 clk = ~clk;
initial begin clk = 0;global_reset_n = 0;@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);@(posedge clk);global_reset_n = 1;
end
endmodule