NEC switch - Manual (Page 137)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
137
(2) Data/handshake packet reception interrupt servicing
INTUSBRD occurrence
RETI
Planned packet
was received?
USB_MODE is SETUP?
USB_MODE is
data stage OUT
reception?
Re-transmit data reception
reservation processing
Transition processing to
status stage OUT reception
USB request processing
USB_MODE is
waiting for communication
request?
ACK reception processing
to ENDPOINT 1
DATA/ACK reception
processing to ENDPOINT 0
Yes
Yes
Yes
No
No
No
No
Yes