英语翻译The cables have different connectors on the hub end and on the device end,to prevent people from accidentally connecting two hub sockets together.When a new I/O device is plugged in,the root hub detects this event and interrupts the opera

英语翻译The cables have different connectors on the hub end and on the device end,to prevent people from accidentally connecting two hub sockets together.When a new I/O device is plugged in,the root hub detects this event and interrupts the opera
英语翻译
The cables have different connectors on the hub end and on the device end,to prevent people from accidentally connecting two hub sockets together.
When a new I/O device is plugged in,the root hub detects this event and interrupts the operating system.The operating system then queries the device to find out what it is and how much USB bandwidth it needs.
Precisely（刚好） every 1.00±0.05 msec (millisecond),the root hub broadcasts a new frame to keep all the devices synchronized in time.A frame is associated with a bit pipe,and consists of packets,the first of which is from the root hub to the device
USB supports four kinds of frames:control,isochronous（同步的）,bulk（批量的）,and interrupt.
Isochronous frames are for real-time devices such as microphones,loudspeakers,and telephones that need to send or accept data at precise time intervals.They have a highly-predictable（可预测的） delay but provide no retransmissions in the event of errors.
A frame consists of one or more packets,possibly some in each direction.Four kinds of packets exist:token,data,handshake,and special.Token packets are from the root to a device and are for system control.
The IN token packet is a poll,asking the device to return certain data.Fields in the IN packet tell which bit pipe is being polled so the device knows which data to return (if it has multiple streams).The OUT token packet
announces that data for the device will follow
The format of a data packet is shown in Figure 1.It consists of an 8-bit synchronization field,an 8-bit packet type (PID),the payload（有效载荷）,and a 16-bit CRC (Cyclic Redundancy Code)（循环冗余校验码） to detect errors.

英语翻译The cables have different connectors on the hub end and on the device end,to prevent people from accidentally connecting two hub sockets together.When a new I/O device is plugged in,the root hub detects this event and interrupts the opera
缆绳有不同的连接器在插孔末端和在设备终端,防止人一起偶然连接二个插孔插口.
当新的I/接通O设备,根插孔查出这个事件并且中断操作系统.操作系统然后询问设备发现什么它是,并且多少USB带宽它需要.
(刚好)精确每1.00±0.05毫秒(毫秒),根插孔在时间播放一个新的框架保留所有设备同步.框架同位管子联系在一起,并且包括小包,一个,其中是从根插孔到设备
USB支持四框架：控制,等时(同步的),大块(批量的),并且中断.
等时的框架是为实时设备例如话筒,扩音器,并且需要送或接受数据在精确间隔时间的电话.他们没有高可预测的(可预测的)在错误情形下,延迟,但提供转播.
框架包括一个或更多小包,可能一些在每个方向.四小包存在：象征,数据,握手,并且特别.象征性的小包是从根到设备并且是为系统控制.
在象征性的小包是民意测验,请求设备退回某些数据.领域在小包告诉哪个位管子投票,因此设备知道返回的哪些数据(如果它有多条小河).出口象征小包
宣布数据为设备在
表1将跟随数据包的格式显示.它包括一个8位同步领域,一个8位小包类型(PID),酬载(有效载荷),并且查出错误的16位CRC (循环多余代码) (循环冗余校验码).