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？
5 |5 t+ v$ Z9 o- The tristate is connected to a black box.
/ W$ B; v0 C2 m, c; C7 ?- The tristate is connected to the output of a block, and the hierarchy of the block is preserved.
( H4 c6 A  L3 h9 P4 J: O- The tristate is connected to a top-level output.
- 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!
- J7 A$ f5 d3 F% \( d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
8 I& S5 l( X- h. z! u" B# J5 B$ M          if(not NCS2 and NCS1 and not A19 and A18 and  not A3 and not A2 and not A1 and not WR) = '1' then
1 h  c  p, J1 b. ~% p             a(0)<=not D(0);
3 o" z7 S2 D6 j! T9 h7 Q             a(1)<=not D(1);
$ i* F! f) M. |" {# U2 v- B             a(2)<=not D(2);
           end if;
             ledg<= a(0);
7 W1 L! I' M4 W, N- t4 j. V             ledy<= a(1);
             ledr<= a(2);
* y, \7 i3 K, q. V9 L* J   end process;
数据读入的程序：
    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';
7 L9 O+ U7 m% [3 O! m5 y9 Q1 O    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';
/ L8 N& i2 D% u1 r0 o: U* P# k. S' [3 @: d    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';
* A+ Q' H4 q3 o    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';
1 ~/ ^. P% j' n    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';
0 e! K" Z; W5 BD(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';
* P" d9 L$ J4 N4 i6 A3 U2 s" [  d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。。