usb的low-powered 和high-powered的.

能否给个结实啊？谢谢了！

高速的自然速度快撒，是用一个通过阻抗为90Ω±15%，最大单路时延为26ns的屏蔽双绞线电缆进行的，其到达的最大速率为12Mb/s，低速的USB设备在插口端必须要有一个带有串行口连接器的可控制电缆，其速率为1.5Mb/s。当然上拉电阻的位置也不一样拉，去找个usb的协议看看嘛，就晓得了。比听别个解释清楚的多

楼上的，人家说的可是高速不是全速哦，不过的确找协议看看才能清楚。

1.1.1.1 (M) The USB modem must pass USB certification criteria for bus powered USB devices.USB certification without waivers is preferred, but waivers for suspend current, and inrush current, are acceptable.1.1.1.2 (M) The USB modem shall have330 mV droop on the power supply line of a neighboring USB slave device when the USB modem is attached to the same USB host.1.1.1.3 (M) The USB modem shall draw no more than 100 mA prior to successful high power USB arbitration.1.1.1.4 (M) The USB modem shall draw nomore than 500 mA after being recognized as a high power USB device.1.1.1.5 (M) The modem shall draw no more than 500 uA while in suspend mode

1.full speed mode 传输速率为12Mbps,一般在D+端通过1.5k电阻上拉至3.3V;2.low speed mode传输速率为1.5Mbps,一般在D-端通过1.5k电阻上拉至3.3V.

我说的不是全速和低速阿，而是low-powered 和high-powered

(M) The USB modem shall draw no more than 100 mA prior to successful high power USB arbitration.
(M) The USB modem shall draw nomore than 500 mA after being recognized as a high power USB device在Device插到USB上时, USB默认Low-Power模式. 这时Host只能提供100mA的电流. 但Device需要更大的电流的话, 会通知Host, 然后Host关闭其他USB口,和其他耗电Device.进入High-Power模式. 可以提供500mA

low-power和high-power的提供的电压没有关系么？只是充电电流么？

这个问题要说明清楚：
是过了枚举的时间后，HUB提供HIGH POWER，还是需要枚举才能提供HIGH POWER！》？

100ma/500ma 是host通知DEVICE，我们设计的充电芯片是由CPU来切换的！