NEC switch - Manual (Page 123)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
123
Figure 8-20. Flowchart of USB Timer Operation (1/2)
SYNC detected?
EOP received?
SETORX
(internal signal)
= 1?
Transmit data
transferring?
Transmit EOP is
output?
DATA TX
(internal signal)
= 1?
Idle state
USB timer reset
USB timer start
(low-speed mode)
USB timer reset
3
IN packet?
INTUSBTM occurred
UWDERR set
(inadvertent program
loop detection)
Low-speed
mode overflow?
1
2 Y
Y
Y
Y
N
N
N
N
Y
Y
SETUP/OUT
packet?
N
N
N
N
N
Y
Y
Y
UWDERR: Bit 7 of packet receive status register (RXSTAT)