综合过程中出现大量的 XST 2677 错误：
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1895 - Due to other FF/Latch trimming, FF/Latch (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:1710 - FF/Latch (without init value) has a constant value of 1 in block . This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
WARNING:Xst:2677 - Node of sequential type is unconnected in block .
可以看出，几乎所有的内部变量综合时都出现了问题，如果把这些内部变量定义在端口中（比如定义为输出）则不会出现这样的问题。实在不知是什么原因。导致错误的部分程序如下：（完整程序见附件）
module LCD_driver(
input clk50,
input reset,
output SF_CE0,
output reg LCD_RS,
output LCD_RW,
output reg LCD_E,
output reg [11:8] SF_D,
output led0,
output led1
);
reg [0:12] main_state;
reg [0:10] init_state;
reg [0:6] timing_state;
reg [11:8] high_nibble,low_nibble;
reg init_init,init_done,tx_init,tx_done;
integer i1,i2,i;
reg LCD_E0,LCD_E1;
reg [11:8]SF_D0,SF_D1;
即：将上面的定义方式改为下面的，就没有出现上述错误。
module LCD_driver(
input clk50,
input reset,
output SF_CE0,
output reg LCD_RS,
output LCD_RW,
output reg LCD_E,
output reg [11:8] SF_D,
output led0,
output led1，
output reg [12:0] main_state,
output reg [10:0] init_state,
output reg [6:0] timing_state
);
reg [0:12] main_state;
reg [0:10] init_state;
reg [0:6] timing_state;
reg [11:8] high_nibble,low_nibble;
reg init_init,init_done,tx_init,tx_done;
integer i1,i2,i;
reg LCD_E0,LCD_E1;
reg [11:8]SF_D0,SF_D1;