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！！
% c& v$ k" {) V' M2 X( L0 sWARNING: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？
- The tristate is connected to a black box.
- The tristate is connected to the output of a block, and the hierarchy of the block is preserved.
- The tristate is connected to a top-level output.
( Q& ?6 n/ z; F! l( {1 G  w* _- 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!
, Q/ _! N; |( `4 h) f9 }$ n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)
) t1 W6 [" P( G+ Y& @         begin
) ^5 o+ t  L- ?" w% k          if(not NCS2 and NCS1 and not A19 and A18 and  not A3 and not A2 and not A1 and not WR) = '1' then
             a(0)<=not D(0);
             a(1)<=not D(1);
9 V1 m3 y6 ]# ]  |: B             a(2)<=not D(2);
. Y( v# z" `4 {! ^9 s& S           end if;
" ^3 y* _  Z; ]3 d7 r             ledg<= a(0);
9 N9 U& k) a; M$ W: g             ledy<= a(1);
. L& j* O8 @' }7 |2 u             ledr<= a(2);
   end process;
, t8 T, i5 f2 V6 Y3 N! w数据读入的程序：
' q' B3 l: U: p. c+ ~    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';
, l. W0 `6 z# `* W# l5 u    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';
    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';
3 o% T0 i0 ]! P! V6 B# ]( e    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。。