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1 USB主机控制器1.1对于主板早期的USB主控制器通过PCI总线与主板连接,现今的USB功能则内建在主板芯片组中。这些基于PCI总线的控制器可处理大量USB事务,例如将PC和多个USB设备之间传输的数据包排序和分级。一个USB事务可产生数十甚至数百个数据包,这些都由主控制器处理。低速和全速设备的控制器称为UHCH/OHCI,高速设备的控制器称为EHCI。1.2对于嵌入式系统
1 USB Host Controller 1.1 For Motherboards The early USB host controller was connected to the motherboard via the PCI bus. Today’s USB features are built into the motherboard chipset. These PCI bus-based controllers handle a large number of USB transactions, such as sorting and ranking data packets transmitted between a PC and multiple USB devices. A USB transaction can generate tens or even hundreds of packets, all handled by the main controller. The controller for low-speed and full-speed devices is called UHCH / OHCI and the controller for high-speed devices is called EHCI. 1.2 for embedded systems