同步FIFO实现

verilog实现两种同步FIFO的方法,非常适合初学者理解时序的控制过程和方法!
理解了这个东西,很多verilog 的实现方法和思想你会有一个深入的理解的!
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★★一种风格的同步FIFO【我最喜欢的同步FIFO风格!】

//8×32bit的同步FIFO

module FIFO_Buffer(
  Data_out,
  stack_full,
  stack_almost_full,
  stack_half_full,
  stack_almost_empty,
  stack_empty,
  Data_in,
  write_to_stack,
  read_from_stack,
  clk,rst
  );
  parameter stack_width=32; //数据位宽
  parameter stack_height=8; //FIFO深度

  parameter stack_ptr_width=3;
  parameter AE_level=2;
  parameter AF_level=6;
  parameter HF_level=4;
  output [stack_width-1:0] Data_out;
 
  output                 stack_full,stack_almost_full,stack_half_full;
  output                 stack_almost_empty,stack_empty;
  input[stack_width-1:0] Data_in;
  input                  write_to_stack,read_from_stack;
  input                  clk,rst;
 
  reg[stack_ptr_width-1:0] read_ptr,write_ptr;
 
  reg[stack_ptr_width:0]   ptr_gap;
  reg[stack_width-1:0]     Data_out;
  reg[stack_width-1:0]     stack[stack_height-1:0];
 
  assign stack_full=(ptr_gap==stack_height);
  assign stack_almost_full=(ptr_gap==AF_level);
  assign stack_half_full=(ptr_gap==HF_level);
  assign stack_almost_empty=(ptr_gap==AE_level);
  assign stack_empty=(ptr_gap==0);
 
  always @(posedge clk or posedge rst)
   if(rst)begin
       Data_out<=0;
       read_ptr<=0;
       write_ptr<=0;
       ptr_gap<=0;
   end

//①只有写入请求且FIFO不满
   else
if(write_to_stack &&(!stack_full)&&(!read_from_stack))begin
       stack[write_ptr]<=Data_in;
       write_ptr<=write_ptr+1;
       ptr_gap<=ptr_gap+1;
   end

//②只有读出请求且FIFO不空
   elseif((!write_to_stack)&&(!stack_empty)&&read_from_stack)begin
       Data_out<=stack[read_ptr];
       read_ptr<=read_ptr+1;
       ptr_gap<=ptr_gap-1;
   end

//同时有写入、读出请求,但FIFO为空,此时仅对写入做处理,同①
   else if(write_to_stack&&read_from_stack&&stack_empty)begin
       stack[write_ptr]<=Data_in;
       write_ptr<=write_ptr+1;
       ptr_gap<=ptr_gap+1;
   end

//同时有写入、读出请求,但FIFO为满,此时仅对读出做处理,同②
   else if(write_to_stack&&read_from_stack&&stack_full)begin
       Data_out<=stack[read_ptr];
       read_ptr<=read_ptr+1;
       ptr_gap<=ptr_gap-1;
   end

//③同时有写入、读出请求且FIFO既不满也不空
   elseif(write_to_stack&&read_from_stack&&(!stack_full)&&(!stack_empty))
   begin
       Data_out<=stack[read_ptr];
       stack[write_ptr]<=Data_in;
       read_ptr<=read_ptr+1;
       write_ptr<=write_ptr+1;
   end

endmodule





//16*16 fifo//
//
方法1
//
module fifo(clock,reset,read,write,fifo_in,fifo_out,fifo_empty,fifo_half,fifo_full);
  input clock,reset,read,write;
  input [15:0]fifo_in;
  output[15:0]fifo_out;
  output fifo_empty,fifo_half,fifo_full;//
标志位
  reg [15:0]fifo_out;
  reg [15:0]ram[15:0];
  reg [3:0]read_ptr,write_ptr,counter;//
指针与计数
  wire fifo_empty,fifo_half,fifo_full;
  
  always@(posedge clock)
  if(reset)
    begin
      read_ptr=0;
      write_ptr=0;
      counter=0;
      fifo_out=0;                    //
初始值
    end
  else
    case({read,write})
      2'b00:
            counter=counter;        //
没有读写指令
      2'b01:                            //
写指令,数据输入fifo
            begin
              ram[write_ptr]=fifo_in;
              counter=counter+1;
              write_ptr=(write_ptr==15)?0:write_ptr+1;
            end
      2'b10:                          //
读指令,数据读出fifo
            begin
              fifo_out=ram[read_ptr];
              counter=counter-1;
              read_ptr=(read_ptr==15)?0:read_ptr+1;
            end
      2'b11:                        //
读写指令同时,数据可以直接输出
            begin
              if(counter==0)
                fifo_out=fifo_in;
              else
                begin
                  ram[write_ptr]=fifo_in;
                  fifo_out=ram[read_ptr];
                  write_ptr=(write_ptr==15)?0:write_ptr+1;
                  read_ptr=(read_ptr==15)?0:write_ptr+1;
                end
              end
        endcase
        
        assignfifo_empty=(counter==0);    //
标志位赋值组合电路
        assign fifo_half=(counter==8);
        assign fifo_full=(counter==15);
      
    endmodule

aaa

//4*16 fifo
//
方法2
//
module fifo_four(clk,rstp,din,readp,writep,dout,emptyp,fullp);
  inputclk;                //
时钟
  inputrstp;               //
复位
  input[15:0]din;           //16
位输入信号
  inputreadp;              //
读指令
  inputwritep;              //
写指令
  output[15:0]dout;         //16
位输出信号
  outputemptyp;            //
空指示信号
  outputfullp;             //
满指示信号
  
  parameter DEPTH=2,MAX_COUNT=2'b11;
  
  reg[15:0]dout;
  reg emptyp;
  reg fullp;
  
  reg[(DEPTH-1):0] tail; //
读指针
  reg[(DEPTH-1):0] head;//
写指针
  reg[(DEPTH-1):0] count; //
计数器
  reg[15:0]fifomem[0:MAX_COUNT]; //
四个16位存储单元
  
  //read
  always@(posedge clk)
    if(rstp==1)    
        dout<=0;  
    else if(readp==1&&emptyp==0)
      dout<=fifomem[tail];
   //write   
  always@(posedge clk)
      if(rstp==1&&writep==1&&fullp==0)
        fifomem[head]<=din;
  
  //
更新head指针
  always@(posedge clk)    
  if(rstp==1)
    head<=0;
  else if(writep==1&&fullp==0)
    head<=head+1;
    
  //
更新tail指针
  always@(posedge clk)    
  if(rstp==1)
    tail<=0;
  else if(readp==1&&emptyp==0)
    tail<=tail+1;
    
  //count
  always@(posedge clk)
  if(rstp==1)
    count<=0;
  else
     case({readp,writep})
     2'b00:
          count<=count;
     2'b01:
          if(count!=MAX_COUNT)
          count<=count+1;
     2'b10:
          if(count!=0)
          count<=count-1;
     2'b11:
          count<=count;
    endcase
    
  //
更新标志位emptyp
  always@(count)
  if(count==0)
     emptyp<=1;
   else
     emptyp<=0;
  
  //
更新标志位tail
  always@(count)
  if(count==MAX_COUNT)
    fullp <=1;
  else
    fullp <=0;
    
endmodule


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网上的代码读数据输出(dataout)部分不受读使能(rd)控制,显然不对,所以稍作修改,欢迎批评

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