On Tue, 28 Feb 2006, Mukund JB. wrote: > Dear Alan, > > >On Tue, 28 Feb 2006, Mukund JB. wrote: > > > >> Dear Alan, > >> > >> I am not speaking about the 'Max Transfers' instead I am talking > about > >> the MAX bottom most row. I did not understand how is max bandwidth > >> jumped to 187500 value. > > > >> >> I understand it suggests that it supports (187500*8) = 1.5Mb/s > data > >> >> rate. > > > >Looks like you do understand it after all. That's the maximum number > of > >bytes per second. It's really just the theoretical maximum, since no > >frame can have more than 187 bytes and so there can't be more than > 187000 > >bytes per second. Even less than that, when you take into accont > >inter-packet delays and bit-stuffing. > > I am really sorry to ask where these 187 bytes came into picture. > Which part of USB specifications says that 187 bytes are the maximum > transferable control transfers bytes per frame?
It's not the maximum transferable control transfers bytes per frame. It's the maximum bytes per frame, period. In other words, since low-speed USB runs at 1.5 Mb/s, that's 1500000 bits per second, or 1500 bits per frame, or 187.5 bytes per frame. Since you can't transfer half a byte, the number is rounded down to 187. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
