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(3)
Transition from Suspend State to Software Standby Mode and Canceling Software
Standby Mode
When the USB bus enters from the suspend state to software standby mode, processing should
proceed as shown below.. When canceling software standby mode, ensure enough time for the
system clock oscillation to be settled.
Transition from suspend state to
software standby mode
Detect that USB bus is in suspend state
(1)
Set SURSF in IFR2 to 1
(2)
(3)
Clear SURSF in IFR2 to 0
(4)
Check if SURSS in IFR2 is set to 1
Clear SURSF in IER2 to 0
(5)
Set SSRSME in IER2 to 1
Shift to software standby mode
(6)
(execute SLEEP instruction)
(7)
Denotation of figures
: Operation by firmware setting
: Automatic operation by LSI hardware
Figure 22.6 Flow of Transition to and Canceling Software Standby Mode
USBINTN interrupt
Stop all clocks of LSI
Section 22 USB Function Module (USB)
Canceling software standby mode
(8)
Detect that USB bus is in resume state
(9)
RESUME interrupt
Cancel software standby mode
(10)
Wait for system clock oscillation to be settled
Clear SURSF in IFR2 to 0
(11)
Check if SURSS in IFR2 is cleared to 0
Set SURSF in IER2 to 1
(12)
Clear SSRSME in IER2 to 0
USB communications can be resumed
through USB registers
Rev. 1.00 Mar. 12, 2008 Page 869 of 1178
REJ09B0403-0100
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