Modelsim10.5SE 仿真时出现大量的如下错误，Google+baidu了下发现命令行设置下就可以关闭这个打印了，记录下。
# ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the result will be 'X'(es).
# Time: 22315 ns Iteration: 7 Instance: /tb_top/RingHUB
# ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the result will be 'X'(es).
# Time: 22335 ns Iteration: 7 Instance: /tb_top/RingHUB
# ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand, the result will be 'X'(es).
# Time: 22355 ns Iteration: 7 Instance: /tb_top/RingHUB
命令如下：
vsim xxxx
set StdArithNoWarnings 1
set NumericStdNoWarnings 1
run -all