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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
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