高手请进 高手

lianzishu

我再作简单处理器程序时遇到下列错误，

ERROR:HDLParsers:813 - "e:/xilinx/project4/scpu/proc.vhd" Line 106. Enumerated value U is missing in select.
ERROR:HDLParsers:164 - "e:/xilinx/project4/scpu/proc.vhd" Line 107. parse error, unexpected MINUS, expecting OPENPAR or TICK or LSQBRACK

这两句程序如下：

  sum<=A+buswire when '0';
       A-buswire when others;
请高手指点！谢谢！