Asynchronous FIFO Verilog Code

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异步FIFO，写的规范。

//==========================================
// Function : Asynchronous FIFO (w/ 2 asynchronous clocks).
// Coder : <a href="http://www.asic-world.com/" style="text-decoration-line: none;">http://www.asic-world.com/</a>
// Date : 4/Jul/2020.
//=========================================
`timescale 1ns/1ps
module aFifo
#(parameter DATA_WIDTH = 8,
ADDRESS_WIDTH = 4,
FIFO_DEPTH = (1 << ADDRESS_WIDTH))
//Reading port
(output reg [DATA_WIDTH-1:0] Data_out,
output reg Empty_out,
input wire ReadEn_in,
input wire RClk,
//Writing port.
input wire [DATA_WIDTH-1:0] Data_in,
output reg Full_out,
input wire WriteEn_in,
input wire WClk,
input wire Clear_in);
/////Internal connections & variables//////
reg [DATA_WIDTH-1:0] Mem [FIFO_DEPTH-1:0];
wire [ADDRESS_WIDTH-1:0] pNextWordToWrite, pNextWordToRead;
wire EqualAddresses;
wire NextWriteAddressEn, NextReadAddressEn;
wire Set_Status, Rst_Status;
reg Status;
wire PresetFull, PresetEmpty;
//////////////Code///////////////
//Data ports logic:
//(Uses a dual-port RAM).
//'Data_out' logic:
always @ (posedge RClk)
if (ReadEn_in & !Empty_out)
Data_out <= Mem[pNextWordToRead];
//'Data_in' logic:
always @ (posedge WClk)
if (WriteEn_in & !Full_out)
Mem[pNextWordToWrite] <= Data_in;
//Fifo addresses support logic:
//'Next Addresses' enable logic:
assign NextWriteAddressEn = WriteEn_in & ~Full_out;
assign NextReadAddressEn = ReadEn_in & ~Empty_out;
//Addreses (Gray counters) logic:
GrayCounter GrayCounter_pWr
(.GrayCount_out(pNextWordToWrite),
.Enable_in(NextWriteAddressEn),
.Clear_in(Clear_in),
.Clk(WClk)
);
GrayCounter GrayCounter_pRd
(.GrayCount_out(pNextWordToRead),
.Enable_in(NextReadAddressEn),
.Clear_in(Clear_in),
.Clk(RClk)
);
//'EqualAddresses' logic:
assign EqualAddresses = (pNextWordToWrite == pNextWordToRead);
//'Quadrant selectors' logic:
assign Set_Status = (pNextWordToWrite[ADDRESS_WIDTH-2] ~^ pNextWordToRead[ADDRESS_WIDTH-1]) &
(pNextWordToWrite[ADDRESS_WIDTH-1] ^ pNextWordToRead[ADDRESS_WIDTH-2]);
assign Rst_Status = (pNextWordToWrite[ADDRESS_WIDTH-2] ^ pNextWordToRead[ADDRESS_WIDTH-1]) &
(pNextWordToWrite[ADDRESS_WIDTH-1] ~^ pNextWordToRead[ADDRESS_WIDTH-2]);
//'Status' latch logic:
always @ (Set_Status, Rst_Status, Clear_in) //D Latch w/ Asynchronous Clear & Preset.
if (Rst_Status | Clear_in)
Status = 0; //Going 'Empty'.
else if (Set_Status)
Status = 1; //Going 'Full'.
//'Full_out' logic for the writing port:
assign PresetFull = Status & EqualAddresses; //'Full' Fifo.
always @ (posedge WClk, posedge PresetFull) //D Flip-Flop w/ Asynchronous Preset.
if (PresetFull)
Full_out <= 1;
else
Full_out <= 0;
//'Empty_out' logic for the reading port:
assign PresetEmpty = ~Status & EqualAddresses; //'Empty' Fifo.
always @ (posedge RClk, posedge PresetEmpty) //D Flip-Flop w/ Asynchronous Preset.
if (PresetEmpty)
Empty_out <= 1;
else
Empty_out <= 0;
endmodule