NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
NUC97
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NAKCLR
No Acknowledge Control
This bit plays a crucial role in any control transfer.
0 = The bit is being cleared by the local CPU by writing zero, the USB device controller
will be responding with NAKs for the subsequent status phase. This mechanism holds
the host from moving to the next request, until the local CPU is also ready to process
the next request.
1 = This bit is set to one by the USB device controller, whenever a setup token is
received. The local CPU can take its own time to finish off any house-keeping work
based on the request and then clear this bit.
Note:
Only when CPU writes
data[1:0] is 2’b10 or 2’b00, this bit can be updated.