DC出错，小白求指教。

桅杆

Warning: The register 'counter_reg[0]' may not be optimally implemented because of a lack of compatible components with correct clock/enable phase. (OPT-1205)
Error: Register 'counter_reg[0]' could not be mapped because sequential output inversion is disabled. (OPT-1218)


实在看不懂是什么错误，希望大家能指点一二，先行谢过。