synthesize时出现的Latch warning，请大侠指点！

yinchb

在ISE中synthesize设计的.v文件时，出现了如下信息：
前仿真已经通过了，这是为什么呢，从RTL report中，的确时看到RGB都被接到了电源VCC上。（IMAGE moduel在我上面发的那个帖子中可以看到）
=========================================================================
*                         Low Level Synthesis                           *
=========================================================================
WARNING:Xst:1293 - FF/Latch  <G_6> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_5> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_0> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_6> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_5> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_4> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_3> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_2> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_1> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_0> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_4> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_3> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_6> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_0> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_1> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_2> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_3> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_4> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <R_5> is constant in block <IMAGE>.
WARNING:Xst:524 - All outputs of the instance <image> of the block <LPM_COUNTER_3> are unconnected in block <IMAGE>.
   This instance will be removed from the design along with all underlying logic
WARNING:Xst:1293 - FF/Latch  <R_7> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_7> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <B_7> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_2> is constant in block <IMAGE>.
WARNING:Xst:1293 - FF/Latch  <G_1> is constant in block <IMAGE>.
Library "C:/Xilinx/data/librtl.xst" Consulted
WARNING:Xst:528 - Multi-source in Unit <top7> on signal <IMAGE_G<5>> not replaced by logic
Sources are: IMAGE_G<6>:G<6>, IMAGE_G<1>:G<1>, IMAGE_G<2>:G<2>, IMAGE_B<7>:B<7>, IMAGE_G<7>:G<7>, IMAGE_G<3>:G<3>, IMAGE_G<4>:G<4>, IMAGE_B<0>:B<0>, IMAGE_B<1>:B<1>, IMAGE_B<2>:B<2>, IMAGE_B<3>:B<3>, IMAGE_B<4>:B<4>, IMAGE_B<5>:B<5>, IMAGE_B<6>:B<6>, IMAGE_G<0>:G<0>, IMAGE_G<5>:G<5>
Signal is stuck at GND
WARNING:Xst:528 - Multi-source in Unit <top7> on signal <IMAGE_R<0>> not replaced by logic
Sources are: IMAGE_R<6>:R<6>, IMAGE_R<7>:R<7>, IMAGE_R<5>:R<5>, IMAGE_R<4>:R<4>, IMAGE_R<3>:R<3>, IMAGE_R<2>:R<2>, IMAGE_R<1>:R<1>, IMAGE_R<0>:R<0>
Signal is stuck at GND
ERROR:Xst:415 - Synthesis failed
cpu : 1.81 / 2.22 s | Elapsed : 1.00 / 2.00 s

bravelu

xst真的很奇怪，这段程序应该没什么错，我试着在synplify里面综合了一下，warning都没有。
不过其实他报的不是生成了latch错，FF/LATCH的意思是触发器或latch。这里显然生成了触发器。
他把你的RGB信号接电源是因为他认为后端模块没有用到这几个信号，所以帮你优化掉了，而实际上不是这样，奇怪。
用其他综合工具试试看吧。