In article <ttqam.47651$db2.44...@edtnps83>, Unruh <unruh-s...@physics.ubc.ca> wrote:
>USB only has one data line. It cannot "do" a DCD line except as another >bit of serial data, interleaved with all the other serial data. >Ie, you are not going to get any good signals for an "interrupt". USB has three different kinds of "pipes": interrupt, bulk, and isochronous. The host is responsible for scheduling the time slots on the bus in which each of these kinds of data can be sent. Serial data, like human-interface-device data, normally uses an interrupt pipe. The design of the driver and the host hardware will establish both lower and upper limits on the latency. (Most are probably designed for high latency, by NTP's standards, and fairly high jitter as well, except on isochronous pipes, since the normal latency requirements for interrupt pipes are determined by the reaction time of the user in front of the keyboard.) -GAWollman -- Garrett A. Wollman | What intellectual phenomenon can be older, or more oft woll...@bimajority.org| repeated, than the story of a large research program Opinions not shared by| that impaled itself upon a false central assumption my employers. | accepted by all practitioners? - S.J. Gould, 1993 _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
