NUC502Apr 30, 2015 Page 92 of 266 Rev 1.16.7.3 Functional Descriptions6.7.3.1 SIE (Serial Interface Engine)The SIE is the front-end of the device controller and handles most of the USB packetprotocol. The SIE typically comprehends signaling up to the transaction level. The functionsthat it handles could include:- Packet recognition, transaction sequencing- SOP, EOP, RESET, RESUME signal detection/generation- Clock/Data separation- NRZI Data encoding/decoding and bit-stuffing- CRC generation and checking (Token and Data)- Packet ID (PID) generation and checking/ decoding- Serial-Parallel/ Parallel-Serial conversion6.7.3.2 UIEThe UIE is the endpoints management. All the operations include Control, Bulk,Interrupt and Isochronous transfer are implemented in it.6.7.3.3 Digital Phase Lock LoopThe bit rate of USB data is 12MHz. The DPLL use the 48MHz which comes from theclock control to lock the input data RXDP and RXDM. The 12MHz bit rate clock is alsoconverted from DPLL.6.7.3.4 Floating De-bounceA USB device may be plug-in or unplug from the USB. In order to monitor the state of aUSB device when it is detached from the USB, the device controller provides hardware de-bounce for USB floating detect interrupt to avoid bounce problems on USB plug in andunplug. Floating detect interrupt appears about 10 ms later than USB plug-in and unplug. Auser can acknowledge USB plug-in/unplug by reading SFR “FLODET”, and shouldunderstand that the flag in “FLODET” represents the current state on the bus without de-bounce. If the user poling this flag to check USB state, he/she must add software de-bounce if necessary.
