Check for 3 bytes 0x00 and SOP to better detect random data

sources/decoding/FullToAxis.vhd

@@ -145,7 +145,7 @@ begin
       sop_found <= '0';
     elsif LinkAligned_240 = '1' then
       if FMdin(32) = '1' then
-        if FMdin(7 downto 0) = Kchar_sop and s_axis_tready = '1' then
+        if FMdin(31 downto 0) = (x"000000"&Kchar_sop) and s_axis_tready = '1' then
           sop_found <= '1';
         end if;
       end if;