They are constructed on their respective hardware device drivers as well as the Host Control software, but with higher levels of integration which can provide the best function of call to system control software rather than to call control register and hardware. 它们均构造在各自的硬件设备驱动程序和主控机软件服务之上,但具有更高的集成度,可为系统控制软件提供功能一级的调用,而不是控制寄存器和硬件层的调用。