
iiiPeriPheraLModuLes1(systeM):CLoCkManageMentunit(CMu)
s1C33L17teChniCaLManuaL
ePson
iii-1-31
III
CMU
iii.1.12.6turningoffosC3duringsLeeP
To turn off OSC3 oscillation during SLEEP mode when operating with OSC3 or PLL as the clock source, follow
the control procedure described below.
1. If the current clock source is PLL, it must be changed to OSC3 and the PLL turned off (see note below).
See Section III.1.12.2, “Changing the Clock Source from PLL to OSC3, then Turning Off the PLL,” for the
procedure to change the clock source.
Stop PLL even if the current clock source is OSC3.
2. Clock Control Protect Register (0x301B24) = 0x96
Disable write protection of the clock control registers.
3. Setting the Clock Option Register (0x301B14)
OSCTM[7:0] (D[15:8]) and TMHSP (D2)
Set the wait time until the oscillation stabilizes after exiting SLEEP mode.
Example: TMHSP = 1, OSCTM[7:0] = 0x40 (wait time = about 26 ms when OSC3 = 20 MHz)
OSC3OFF (D3/0x301B14) = 1
Turn off OSC3 oscillation when in SLEEP mode.
WAKEUPWT (D0/0x301B14) = 1
Set the CPU to awake from SLEEP mode by using an RTC interrupt, NMI, or other interrupt from an
external device.
4. Clock Control Protect Register (0x301B24) = other than 0x96
Reenable write protection of the clock control registers.
5. Stop any peripheral circuits that are operating, except the RTC.
6. Execute the slp instruction.
The chip enters SLEEP mode and the CMU temporarily stops clock output.
The CPU is reawaken from SLEEP mode by an RTC interrupt, forced break from the debugger, NMI, or other
interrupt from an external device. After the set oscillation start wait time elapses, the CPU restarts using the
same clock source (OSC3) that was selected before entering SLEEP mode.
7. If the application needs PLL as the clock source, change the clock source to PLL after the CPU wakes up with
the OSC3 clock (see note below).
See Section III.1.12.1, “Changing the Clock Source from OSC3 to PLL,” for the procedure to change the clock
source.
note: ToturntheOSC3oscillationoffinSLEEPmode,theconditionsshownbelowmustbesatisfied
beforeenteringSLEEPmodeandatwakeupfromSLEEPmode.
TheCPUoperateswithOSC3astheclocksource.
ThePLLhasbeenturnedoff.
IfbothOSC3andPLLturnonatwakeupfromSLEEPmodeandtheCPUstartsoperatingwith
PLLastheclocksource,thePLLoperationmaybecomeunstable.
Therefore,tosetPLLastheclocksource,steps1and7abovearerequired.