RE: [usb] Regarding Frames and Microframes

[Bo <bo_ye@yahoo.com>]

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


--- Thierry LEROUX <tleroux@eldim.fr> wrote:
> Hi,
> These frames are "token only" transactions. They do
> not need any ACK or NAK
> to be handled.
> There is a 8 bits PID + 11 bits of frame # + 5 bits
> CRC (= 3 Bytes).
> The Frame # is a 11 bits system wide time frame. Use
> of it is function
> dependent. You can imagine to use it to maintain a
> common system wide time
> frame (For example to synchronise audio equipments
> ...).
> The "tick" time is 1 ms.
> In addition, there is µ-frame ticks (125 µs) if the
> function is 2.0
> compatible. In that case you need some local
> computation to create a 15 bits
> counter.
> We found this SOF very useful for synchronization
> over the whole bus and
> between connected devices.
>  
> I hope this help.
>  
> Thierry
> 
> -----Original Message-----
> From: Veeresh [mailto:veeresh@umsl-india.com] 
> Sent: lundi 25 février 2002 19:57
> To: usb@opencores.org
> Subject: [usb] Regarding Frames and Microframes
> 
> 
> Hi all,
>  
>      I am Veeresh newly joined this mailing list.
> While going through the
> USB Spec. 2.0, I got some doubts in Start Of Frame
> (SOF). As these frames
> are token only transactions, what is the
> significance of these frames? What
> the 11-bit frame indicates?
>  
> Thanks and regards,
> Veeresh
> 
> 


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