Re: [usb] Regarding Frames and Microframes

[Rudolf Usselmann <rudi@asics.ws>]

On Wednesday 27 February 2002 06:17 am, you wrote:
> What will happen if the transaction reach the
> 1ms boundary? Does the host insert the SOF
> packet and redo the current transaction, For
> example "Bulk in transfer"?
>
> regards
> bo


This should never happen. The host must allocate the bandwidth
across all devices attached to it. It has to make sure it does not
"over" allocate the available bandwidth and limit all transactions
(including bulk). This is usually done during SETUP, where it will
negotiate with each device the maximum transfer size. That way
it know the maximum time a transfer will take and not perform the
transfer if it will cross a time slot boundary. think of it as a virtual
TDM protocol !

On the other hand if it ever does happen, the device must be able
to skip a number of SOF frames. I believe there is a threshold as
well, where if it misses N number of SOF frames it may have to go
through SETUP again - I don't remember the details ...

regards,
rudi


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