Expand description
Field SOF reader - Start of frame This bit signals the beginning of a new USB frame and it is set when a SOF packet arrives through the USB bus. The interrupt service routine may monitor the SOF events to have a 1Â ms synchronization event to the USB host and to safely read the USB_FNR register which is updated at the SOF packet reception (this could be useful for isochronous applications). This bit is read/write but only ’0 can be written and writing ’1 has no effect.