日常记录（9）异步FIFO相关

always  @(wptr or winc)  
begin: Gray_inc
  integer i;
  for(i=0; i<=ADDRSIZE; i=i+1)
    wbin[i]= ^ (wptr>>i);      //grey to binary
  if (!wfull)
    wbnext = wbin+winc;      //FIFO
  else
    wbnext = wbin;
  wgnext=(wbnext>>1) ^ wbnext;  //binary to grey
end

  wfull <= ((wgnext[ADDRSIZE] !==wrptr2[ADDRSIZE])&&(w_2ndmsb== wr_2ndmsb)
             && (wgnext[ADDRSIZE-2:0]== wrptr2[ADDRSIZE-2:0]));