请教，异步fifo设计时遇到一个问题

代码比较简单
assign    usedword=(wptr>rptr)?(wptr-rptr)full?4'hFempty?4'h016-rptr+wptr)));
always @ (posedge w_clk or posedge clear)
if(clear)
  begin
   wptr<=4'h0;
   pwptr<=4'h0;
  end
else if(！full && wr) begin
  mem[wptr]<=data_in;
  pwptr<=wptr;
  wptr<=(&wptr)?4'h0:(wptr+1);
end   
always @ (posedge r_clk or posedge clear)
if(clear)
  begin
   rptr<=4'h0;
   prptr<=4'h0;
   data_out<=8'h00;
  end
else if(！empty && rd) begin
  data_out<=mem[rptr];
  prptr<=rptr;
  rptr<=(&rptr)?4'h0:(rptr+1);
end
reg  n_full=1'b0;
assign full=(wptr==rptr)?n_full:1'b0;
assign empty=(wptr==rptr)?(~n_full):1'b0;
always @ (posedge w_clk or posedge r_clk)
if(w_clk)    n_full<=(wptr==prptr);
else          n_full<=(wptr==prptr);  
但在门级仿真时问题来多了，如图中所示

门级仿真

在写时钟的上升沿，wptr=2,prptr=3,此时n_full变为了高?

你的指针怎么没做跨时钟域处理?

always @ (posedge w_clk or posedge r_clk)
if(w_clk)    n_full<=(wptr==prptr);
else          n_full<=(wptr==prptr);  
这代码啥意思?

没做跨时钟域处理：因為跨時域所以pointer在門級仿真做相互比對時會有問題
，上網看一下跨時域的的處理
1.cross clock domain, need double sync
2. use "gray code" to pass data bus