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https://designers-guide.org/forum/YaBB.pl Design >> High-Speed I/O Design >> USB 2.0 Low Speed Buffer Up/Down Stream Difference https://designers-guide.org/forum/YaBB.pl?num=1275610250 Message started by neoflash on Jun 3rd, 2010, 5:10pm |
Title: USB 2.0 Low Speed Buffer Up/Down Stream Difference Post by neoflash on Jun 3rd, 2010, 5:10pm Why in USB 2.0 spec, the drive loading capability is different between up and down steam facing ports? For downstream, it is 200-600pF while for upstream it is 50-150pF? |
Title: Re: USB 2.0 Low Speed Buffer Up/Down Stream Difference Post by casual on Jun 11th, 2010, 6:14am It gives more stringent rules to downstream ports (host & HUB) since they have power supply. While upstream ports normally is a device which get power from host or HUB. So their driving capability is less. Hopefully it is correct. |
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