用移位寄存器實現(xiàn)同步FIFO

????????如圖所示，同步FIFO帶有push信號和pop信號，push代表往隊列里面壓入一個數(shù)據(jù)，pop代表往隊列外面排出一個數(shù)據(jù)。

?解題思路

? ? ? ? 同步FIFO的空滿判斷用一個計數(shù)器來判斷，收到push信號計數(shù)器加1，收到pop信號時計數(shù)器減1，考慮同時push和pop的情況計數(shù)器不變，當(dāng)計數(shù)器為0時，輸出空，當(dāng)計數(shù)器為DEPTH時，輸出滿。FIFO給出空滿信號，空時不能讀，滿時不能寫。具體代碼如下：

always @(posedge clk)begin
    if(!rstn)
        counter <= 'd0;
    else if(push && pop)
        counter <= counter;
    else if(push)
        counter <= counter + 1'b1;
    else if(pop)
        counter <= counter - 1'b1;
end

assign empty = (counter == 'd0);
assign full  = (counter == DEPTH);

? ? ? ? ?數(shù)據(jù)的寫入和讀出，push數(shù)據(jù)就直接在移位寄存器的一端，用拼接符號把數(shù)據(jù)拼接在一起。pop數(shù)據(jù)輸出DEPTH-counter位置的數(shù)據(jù)，因為我們位拼接是從高位開始拼接的，要注意讀出的地址位置。

always @(posedge clk)begin
      if(!rstn)
        pop_data <= 'd;
      else if(push && pop)begin
        fifo_mem <= {push_data,fifo_mem[DEPTH-1:1]};
        pop_data <= fifo_mem[DEPTH-counter];
      end
      else if(push)begin
        fifo_mem <= {push_data,fifo_mem[DEPTH-1:1]};
      end
      else if(pop)begin
        pop_data <= fifo_mem[DEPTH-counter];
      end
end

代碼

module shift_reg_fifo#(
    parameter DEPTH  = 8    ,
    parameter DATA_W = 32
)(
    input                      clk          ,
    input                      rstn         ,
    output                     empty        ,
    output                     full         ,

    input                      push         ,
    input      [DATA_W-1:0]    push_data    ,
    input                      pop          ,
    output reg [DATA_W-1:0]    pop_data    
);
reg [DATA_W-1:0] fifo_mem [DEPTH-1:0];
reg [$clog2(DEPTH)+1:0] counter;

always @(posedge clk)begin
      if(!rstn)
        pop_data <= 'd;
      else if(push && pop)begin
        fifo_mem <= {push_data,fifo_mem[DEPTH-1:1]};
        pop_data <= fifo_mem[DEPTH-counter];
      end
      else if(push)begin
        fifo_mem <= {push_data,fifo_mem[DEPTH-1:1]};
      end
      else if(pop)begin
        pop_data <= fifo_mem[DEPTH-counter];
      end
end

always @(posedge clk)begin
    if(!rstn)
        counter <= 'd0;
    else if(push && pop)
        counter <= counter;
    else if(push)
        counter <= counter + 1'b1;
    else if(pop)
        counter <= counter - 1'b1;
end

assign empty = (counter == 'd0);
assign full  = (counter == DEPTH);

endmodule

testbench

`timescale 1ns/1ps
module tb#(
    parameter DEPTH  = 8    ,
    parameter DATA_W = 32   
)();
reg clk,rstn;
wire empty,full;
wire [DATA_W-1:0] pop_data;

reg push,pop;
reg [DATA_W-1:0] push_data;

initial begin
    forever #5 clk = ~clk;
end

initial begin
    clk  =  1'b0;
    rstn =  1'b0;
    pop  =  1'b0;
    push = 1'b0;
    push_data =  32'd0;
    #10
    rstn =  1'b1;
    #16
    repeat(8)begin
        #10 
        push =  1'b1;
        push_data = $random%32;
    end
    #10
    push = 1'b0;
    repeat(8)begin
        #10
        pop =  1'b1;
    end
    #10
    pop =  1'b0;
    repeat(3)begin
        #10
        pop  = 1'b0;
        push =  1'b1;
        push_data = $random() % 10'd32;
        #10
        push = 1'b0;
        pop  = 1'b1;
    end
    #10
    pop = 1'b0;
    push = 1'b1;
    push_data = $random() % 10'd32;
    repeat(4)begin
        #10
        pop  = 1'b1;
        push = 1'b1;
        push_data = $random() % 10'd32;
    end
    #10
    pop = 1'b0;
    push = 1'b0;
    #50
    $finish();
end

initial begin
    $fsdbDumpfile("shift_fifo.fsdb");
    $fsdbDumpvars(0);
end

shift_reg_fifo #(
    .DEPTH  (DEPTH  ),
    .DATA_W (DATA_W )
)u_shift_reg_fifo(
    .clk        (clk        ),
    .rstn       (rstn       ),
    .empty      (empty      ),
    .full       (full       ),

    .push       (push       ),
    .push_data  (push_data  ),
    .pop        (pop        ),
    .pop_data   (pop_data   )
);

endmodule

? ? ? ? 仿真部分，在深度為8的情況下，我們分別模擬了寫入8個數(shù)據(jù)到寫滿，讀出8個數(shù)據(jù)直到讀空，接著連續(xù)寫讀3次，然后寫入1個數(shù)據(jù)（保證下一步同時讀寫時，F(xiàn)IFO不為空，能讀出數(shù)據(jù)）。再同時讀寫4次。

波形圖

?文章來源地址http://www.zghlxwxcb.cn/news/detail-630049.html

到了這里，關(guān)于用移位寄存器實現(xiàn)同步FIFO，帶空滿判斷的文章就介紹完了。如果您還想了解更多內(nèi)容，請在右上角搜索TOY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！