ram的使用——初始化很重要

背景

ram是非常常用的ip，前人的经验告诉我们，如果不对ram进行初始化直接读写，不定态在实际上板时会出现不可预知的问题。

我们需要对ram进行初始化写0操作，代码如下。需要注意，复位释放时立马写入可能存在复位抖动的造成ram写入失败的问题，因此可以选择复位后增加一定的延时。

当inital_done信号拉高以后才允许系统开始工作。

下面是复位初始化ram的代码：

parameter C_ADDR = 10;//ram地址位宽 DEPTH = 1024
parameter C_WIDTH = 10;//ram数据位宽

reg                 s_initial_delay_flag    ;  //延迟标志
reg [6:0]           s_initial_delay_cnt     ;  //延迟计数器 128 clk

reg [C_ADDR-1:0]    s_init_ram_addr         ;  //初始化写地址
reg                 s_init_ram_wr           ;  //初始化写势能信号

reg                 s_ram_initial_done      ;  //初始化完成标志
always@(posedge i_clk)begin
    if(i_rst)begin
        s_initial_delay_cnt <= 7'd0;
        s_initial_delay_flag <= 1'b0;
    end
    else if(s_initial_delay_cnt == 7'b111_1111)begin//计数器结束条件
        s_initial_delay_cnt <= s_initial_delay_cnt;
        s_initial_delay_flag <= 1'b1;
    end
    else begin
        s_initial_delay_cnt <= s_initial_delay_cnt + 7'd1;
        s_initial_delay_flag <= s_initial_delay_flag;
    end
end

always@(posedge i_clk)begin
    if(i_rst)begin
        s_init_ram_addr <= 7'd0;
        s_init_ram_wr <= 1'b0;
        s_ram_initial_done <= 1'b0;
    end
    else if(s_init_ram_addr == {C_ADDR-1{1'b1}})begin//
        s_init_ram_addr <= s_init_ram_addr;
        s_init_ram_wr <= 1'b0;
        s_ram_initial_done <= 1'b1;
    end
    else if(s_initial_delay_flag) begin
        s_init_ram_addr <= s_init_ram_addr + 7'd1;
        s_init_ram_wr <= 1'b1;
        s_ram_initial_done <= 1'b0;
    end
end
//例化ram
//initial data = {C_WIDTH-1{1'b0}}