OTG host frame number/frame time remaining register
FRNUM | Frame number This field increments when a new SOF is transmitted on the USB, and is cleared to 0 when it reaches 0x3FFF. |
FTREM | Frame time remaining Indicates the amount of time remaining in the current frame, in terms of PHY clocks. This field decrements on each PHY clock. When it reaches zero, this field is reloaded with the value in the Frame interval register and a new SOF is transmitted on the USB. |