Datasheet

Section 14 Universal Serial Bus (USB)
Rev.7.00 Dec. 24, 2008 Page 505 of 698
REJ09B0074-0700
(4) Remote-Wakeup Interrupt Processing
Figure 14.10 is a flowchart of remote-wakeup interrupt processing.
USB function
Firmware
Remote-wakeup
interrupt processing
USB operating clock stabilization
detection interrupt processing
Start USB operating
clock oscillation
Output resume signal
to USB bus
A suspend/resume
interrupt occurs
A USB operating clock
stabilization detection
interrupt occurs
Wait for resume signal
from up-stream
Clear USB operating clock
stabilization detection flag
(Clear CK48READY
in UIFR3 to 0)
Execute remote-wakeup
(Set DVR in UDRR to 1)
Resume interrupt
processing
(see figure 14.8)
Clear USB module
stop mode
(Clear SPRSi in UIFR3
to 0)
Wait for USB operating
clock stabilization
Resume main process
USB operating
clock stabilization time
has passed?
Yes
Yes
No
EXIRQx
IRQ6
No
Is remote-
wakeup enabled
by host?
NMI or IRQx
Remote-
wakeup
Figure 14.10 Example Flowchart of Remote-Wakeup Interrupt Processing