On Thu, 9 Mar 2006, Mukund JB. wrote: > Dear Linux USB Devels, > > I have studied the USB Specifications document till the chapter 5 i.e > USB data flow model and bit and pieces of rest of the Spec. > > Being a novice to USB protocol, I have a set of few queries. Please help > me clear those. > > 1) Transfer means transfer of data between the host and the device which > mat involve one of more transactions. Am I right?
Yes. > 2) In isochronous transfers sections as in 5.6, the tables convey that > there can be more that one isochronous transactions per micro(frame). > But the test in the 5.6.4 bus access constraints say that only one > transaction is possible per micro(frame). > > See the text below: > ------------------- > This allows full-/high-speed isochronous transfers to have rates slower > than one transaction per (micro)frame. However, an isochronous endpoint > must be prepared to handle poll rates faster than the one specified. A > host must not issue more than 1 transaction in a (micro)frame for an > isochronous endpoint unless the endpoint is high-speed, high-bandwidth. > > Can you please make this clear to me? The text says that there can be only one transaction per (micro)frame for an iso endpoint. But there can be more than one iso transaction in a (micro)frame if each transaction is for a different endpoint. > 3) Altinterface setting general application: on receiving the > set_interface request, will (can) the firmware change endpoint setting > like payload size and direction? Yes. > Is this the main application of > Altinterface setting? It's one of them. Other things can change too: the transfer period and whether an endpoint is enabled at all (note that iso endpoints are never supposed to be enabled in altsetting 0). 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
