Dear Alan, Thanks for the response. >> >> 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.
I agree for low speed devices, the max allowable bandwidth for all low speed device put together is 1.5Mb/s. Please see last row of the table below: 8 24000 30% 3 19 24 --> last but one row As you said, for 8 bytes payload the max transfer possible are 3 and so maximum bytes/Frame are (3*8) = 24 bytes. In a similar way what are the values "payload" and "max transfers" to get the bytes/Frame as 187. Max 187500 187 --> last row Hope I am clear. Thanks & Regards, Mukund Jampala ------------------------------------------------------- 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&kid0944&bid$1720&dat1642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
