Re: DLT_ request

[Scott Deandrea <sdeandrea () apple com>]

An interrupt is generated when the frame number rolls over and we use this to increment the upper bits so the frame 
number can grow beyond 11 bits.  This allows software consuming the frame number not to worry about the frame wrap when 
scheduling isochronous I/O.

Yes, time *at* which…

—scott

> On Jan 5, 2017, at 9:35 PM, Guy Harris <guy () alum mit edu> wrote:
>
> > On Jan 5, 2017, at 8:42 PM, Scott Deandrea <sdeandrea () apple com> wrote:
> >
> > The frameNumber is a USB spec defined value that correlates with the start-of-frame packets frame number as defined 
> > in section 8.4.3 Start-of-Frame Packets.
>
> So only 11 of the 64 bits are used?
>
> > The ioTimestamp is in the same Mach Absolute Time.
>
> So that's "Time *at* which the frame completed", rather than "Time *in* which..."?
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