NEC switch - Manual (Page 136)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
136
8.7.2 Interrupt servicing flow
(1) USB token packet reception interrupt servicing
INTUSBRT occurrence
RETI
Receive error occurred?
Receive token is OUT?
Waiting for OUT token?
OUT to ENDPOINT 1?
Receive token is
SETUP?
Receive token is
unplanned token?
IN token reception
to ENDPOINT 1?
IN token reception
processing to ENDPOINT 0
OUT token reception
processing when status stage
IN or data stage IN is received
IN token reception
processing to ENDPOINT 1
OUT token reception
processing to ENDPOINT 1
OUT token reception
processing
Token mismatch
processing
SETUP token
reception processing
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No