AXI Buffer

module example_a_m_axi_buffer
#(parameter
    MEM_STYLE  = "block",
    DATA_WIDTH = 32,
    ADDR_WIDTH = 5,
    DEPTH      = 32
) (
    // system signal
    input  wire                  clk,
    input  wire                  reset,
    input  wire                  sclk_en,

    // write
    output wire                  if_full_n,
    input  wire                  if_write_ce,
    input  wire                  if_write,
    input  wire [DATA_WIDTH-1:0] if_din,

    // read
    output wire                  if_empty_n,
    input  wire                  if_read_ce,
    input  wire                  if_read,
    output wire [DATA_WIDTH-1:0] if_dout
);
//------------------------Parameter----------------------

//------------------------Local signal-------------------
(* ram_style = MEM_STYLE *)
reg  [DATA_WIDTH-1:0] mem[0:DEPTH-1];
reg  [DATA_WIDTH-1:0] q_buf = 1'b0;
reg  [ADDR_WIDTH-1:0] waddr = 1'b0;
reg  [ADDR_WIDTH-1:0] raddr = 1'b0;
wire [ADDR_WIDTH-1:0] wnext;
wire [ADDR_WIDTH-1:0] rnext;
wire                  push;
wire                  pop;
reg  [ADDR_WIDTH-1:0] usedw = 1'b0;
reg                   full_n = 1'b1;
reg                   empty_n = 1'b0;
reg  [DATA_WIDTH-1:0] q_tmp = 1'b0;
reg                   show_ahead = 1'b0;
reg  [DATA_WIDTH-1:0] dout_buf = 1'b0;
reg                   dout_valid = 1'b0;


//------------------------Instantiation------------------

//------------------------Task and function--------------

//------------------------Body---------------------------
assign if_full_n  = full_n;
assign if_empty_n = dout_valid;
assign if_dout    = dout_buf;
assign push       = full_n & if_write_ce & if_write;
assign pop        = empty_n & if_read_ce & (~dout_valid | if_read);
assign wnext      = !push                ? waddr :
                    (waddr == DEPTH - 1) ? 1'b0  :
                    waddr + 1'b1;
assign rnext      = !pop                 ? raddr :
                    (raddr == DEPTH - 1) ? 1'b0  :
                    raddr + 1'b1;

// waddr
always @(posedge clk) begin
    if (reset == 1'b1)
        waddr <= 1'b0;
    else if (sclk_en)
        waddr <= wnext;
end

// raddr
always @(posedge clk) begin
    if (reset == 1'b1)
        raddr <= 1'b0;
    else if (sclk_en)
        raddr <= rnext;
end

// usedw
always @(posedge clk) begin
    if (reset == 1'b1)
        usedw <= 1'b0;
    else if (sclk_en)
        if (push & ~pop)
            usedw <= usedw + 1'b1;
        else if (~push & pop)
            usedw <= usedw - 1'b1;
end

// full_n
always @(posedge clk) begin
    if (reset == 1'b1)
        full_n <= 1'b1;
    else if (sclk_en)
        if (push & ~pop)
            full_n <= (usedw != DEPTH - 1);
        else if (~push & pop)
            full_n <= 1'b1;
end

// empty_n
always @(posedge clk) begin
    if (reset == 1'b1)
        empty_n <= 1'b0;
    else if (sclk_en)
        if (push & ~pop)
            empty_n <= 1'b1;
        else if (~push & pop)
            empty_n <= (usedw != 1'b1);
end

// mem
always @(posedge clk) begin
    if (push)
        mem[waddr] <= if_din;
end

// q_buf
always @(posedge clk) begin
    q_buf <= mem[rnext];
end

// q_tmp
always @(posedge clk) begin
    if (reset == 1'b1)
        q_tmp <= 1'b0;
    else if (sclk_en)
        if (push)
            q_tmp <= if_din;
end

// show_ahead
always @(posedge clk) begin
    if (reset == 1'b1)
        show_ahead <= 1'b0;
    else if (sclk_en)
        if (push && usedw == pop)
            show_ahead <= 1'b1;
        else
            show_ahead <= 1'b0;
end

// dout_buf
always @(posedge clk) begin
    if (reset == 1'b1)
        dout_buf <= 1'b0;
    else if (sclk_en)
        if (pop)
            dout_buf <= show_ahead? q_tmp : q_buf;
end

// dout_valid
always @(posedge clk) begin
    if (reset == 1'b1)
        dout_valid <= 1'b0;
    else if (sclk_en)
        if (pop)
            dout_valid <= 1'b1;
        else if (if_read_ce & if_read)
            dout_valid <= 1'b0;
end

endmodule

code is generated from Xilinx Vivado HLS

 

full_n : queue is not full which means enqueuing is available

empty_n : queue is not empty which means pop is available