求助：一个xilinx警告，请大家指点下！！

zhry

小弟刚用ise，综合时产生了一个警告，不太明白，希望高手能指点下，多谢了！！
WARNING:Xst:2183 - Unit actel: the following tristate(s) are NOT replaced by logic (Please refer to Answer Record 20048 for more information): D<0>_MLTSRCEDGE, D<1>_MLTSRCEDGE, D<2>_MLTSRCEDGE, D<3>_MLTSRCEDGE, D<4>_MLTSRCEDGE, D<5>_MLTSRCEDGE, D<7>_MLTSRCEDGE.

oxygen

看看你的设计属于下面的哪种情况？
+ P0 n& p! k# i% L- The tristate is connected to a black box.
7 X" o) H$ y" n- The tristate is connected to the output of a block, and the hierarchy of the block is preserved.
# [! o6 g7 X! D7 s2 `9 ^8 O- The tristate is connected to a top-level output.
) r# a) f1 R6 i  |2 P* [- The "tristate2logic" constraint is set to "no" on the block where tristates are placed or on the signals to which tristates are connected.

zhry

版主您好！非常感谢您的回复!
" {, d. w6 b7 F6 _您说的这段我也看到过，但是看不太明白。数据线D ：inout std_logic_vector(7 downto 0),类型为inout数据输出的程序：
   process(NCS2 ,NCS1,A19,A18,A3,A2,A1,WR,D)
         begin
9 b# Q+ [# [4 y) P) q          if(not NCS2 and NCS1 and not A19 and A18 and  not A3 and not A2 and not A1 and not WR) = '1' then
' i. d) @, b, a" m# h             a(0)<=not D(0);
             a(1)<=not D(1);
% Y0 z1 q2 J+ _8 Q0 x" [             a(2)<=not D(2);
2 W/ _4 l, N1 f           end if;
             ledg<= a(0);
             ledy<= a(1);
& s, }+ `/ A" N) _+ t1 p             ledr<= a(2);
8 x. h+ [5 B5 P( `   end process;
数据读入的程序：
4 Y2 J/ T+ ?3 W: `. `' Y) M    D(7)<= not oct when(not NCS2 and NCS1 and not A19 and A18 and  not A3 and not A2 and not A1 and not RD) = '1' else 'Z';
% H! @' i! p' S4 P    D(5)<=keyval(0) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
/ R, G+ y, G6 t  s    D(4)<=keyval(1) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
    D(3)<=keyval(2) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
    D(2)<=keyval(3) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
    D(1)<=keyval(4) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
D(0)<=keyval(5) when (not NCS2 and NCS1 and not A19 and A18 and  not A3 and  A2 and  A1 and not RD)='1' else 'Z';
就是这里出的问题，我把数据读入的程序注释掉，这个警告就没了！请问这是什么原因呢？

oxygen

好长的组合逻辑。。如果可以请改为同步设计。。