UM0306 USB full speed device interface (USB)
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USB frame number register ()
Address Offset: 48h
Reset Value: 0000 0xxx xxxx xxxxb (0xxxh)
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RXDP RXDM LCK LSOF[1:0] FN[10:0]
rrrr rrrrrrrrrrr r
Bit 15
RXDP: Receive Data + Line Status
This bit can be used to observe the status of received data plus upstream port data
line. It can be used during end-of-suspend routines to help determining the wake-up
event.
Bit 14
RXDM: Receive Data - Line Status
This bit can be used to observe the status of received data minus upstream port data
line. It can be used during end-of-suspend routines to help determining the wake-up
event.
Bit 13
LCK: Locked
This bit is set by the hardware when at least two consecutive SOF packets have been
received after the end of an USB reset condition or after the end of an USB resume
sequence. Once locked, the frame timer remains in this state until an USB reset or
USB suspend event occurs.
Bits 12:11
LSOF[1:0]: Lost SOF
These bits are written by the hardware when an ESOF interrupt is generated, counting
the number of consecutive SOF packets lost. At the reception of an SOF packet, these
bits are cleared.
Bits 10:0
FN[10:0]: Frame Number
This bit field contains the 11-bits frame number contained in the last received SOF
packet. The frame number is incremented for every frame sent by the host and it is
useful for Isochronous transfers. This bit field is updated on the generation of an SOF
interrupt.
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