Datasheet

Section 16 USB Function Module (USB)
Page 994 of 1408 R01UH0309EJ0500 Rev. 5.00
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
(3) Transition from Suspend State to Software Standby Mode and Canceling Software
Standby Mode
If the USB bus enters from the suspend state to software standby mode, perform the operation as
shown in figure 16.7. When canceling software standby mode, ensure enough time for the system
clock oscillation to be settled.
Transition from suspend state to
software standby mode
(1)
(2)
(3)
(4)
(5)
(8)
(9)
Detect that USB bus is in suspend state.
USBINTN interrupt
Clear SURSF in IFR0 to 0.
Check if SURSS in IFR0 is set to 1.
Clear SURSFE in IER0 to 0.
Set SSRSME in IER0 to 1.
Shift to software standby mode.
(Execute SLEEP instruction.)
Stop all clocks of LSI.
Canceling software standby mode
Detect that USB bus is in resume state.
RESUME interrupt
Cancel software standby mode
Wait for system clock oscillation to be settled.
Wait for 48-MHz USB clock oscillation to be
settled.
Clear SURSF in IFR0 to 0.
Check if SURSS in IFR0 is cleared to 0.
Set SURSFE in IER0 to 1.
Clear SSRSME in IER0 to 0.
USB communications can be resumed
through USB registers.
Denotation of figures
: Operation by firmware setting
: Automatic operation by LSI hardware
(7)
(6)
Stop 48-MHz USB clock.
Set MSTP17 in EXMSTPCRL to 1.
(10)
(11)
(12)
(15)
(16)
(17)
Supply 48-MHz USB clock.(14)
Clear MSTP17 in EXMATPCRL to 0.
(13)
Set SURSF in IFR0 to 1.
Figure 16.7 Flow of Transition to and Canceling Software Standby Mode