Holtek HT66F0175 - Fast Wake-�P

Rev. 1.50 48 August 28, 2017 Rev. 1.50 49 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
Fast Wake-up
TominimisepowerconsumptionthedevicecanentertheSLEEPorIDLE0Mode,wherethesystem
clocksourcetothedeviceswillbestopped.Howeverwhenthedevicesarewokenupagain,itcan
takeaconsiderabletimefortheoriginalsystemoscillatortorestart,stabiliseandallownormal
operationtoresume.ToensurethedevicesareupandrunningasfastaspossibleaFastWake-
upfunctionisprovided,whichallowsf
SUB
,namelyeithertheLXTorLIRCoscillator,toactasa
temporaryclocktorstdrivethesystemuntiltheoriginalsystemoscillatorhasstabilised.Asthe
clocksourcefortheFastWake-upfunctionisf
SUB
,theFastWake-upfunctionisonlyavailablein
theSLEEP1andIDLE0modes.WhenthedevicesarewokenupfromtheSLEEP0mode,theFast
Wake-upfunctionhasnoeffectbecausethef
SUB
clockisstopped.TheFastWake-upenable/disable
functioniscontrolledusingtheFSTENbitintheSMODregister.
IftheHXToscillatorisselectedastheNORMALModesystemclock,andiftheFastWake-up
functionisenabled,thenitwilltakeonetotwot
SUB
clockcyclesoftheLIRCorLXToscillatorfor
thesystemtowake-up.Thesystemwilltheninitiallyrununderthef
SUB
clocksourceuntil512HXT
clockcycleshaveelapsed,atwhichpointtheHTOagwillswitchhighandthesystemwillswitch
overtooperatingfromtheHXToscillator.
IftheHIRCoscillatororLIRCoscillatorisusedasthesystemoscillatorthenitwilltake15~16
clockcyclesoftheHIRCor1~2cyclesoftheLIRCtowakeupthesystemfromtheSLEEPor
IDLE0Mode.TheFastWake-upbit,FSTENwillhavenoeffectinthesecases.
System
Oscillator
FSTEN
Bit
Wake-up Time
(SLEEP0 Mode)
Wake-up Time
(SLEEP1 Mode)
Wake-up Time
(IDLE0 Mode)
Wake-up Time
(IDLE1 Mode)
HXT
0 128 HXT cycles 128 HXT cycles 1~2 HXT cycles
1 128 HXT cycles
1~2 f
SUB
cycles
(System runs with f
SUB
rst for 512 HXT cycles and
then switches over to run with the HXT clock)
1~2 HXT cycles
HIRC x 15~16 HIRC cycles 15~16 HIRC cycles 1~2 HIRC cycles
LIRC x 1~2 LIRC cycles 1~2 LIRC cycles 1~2 LIRC cycles
LXT x 128 HXT cycles 1~2 LXT cycles 1~2 LXT cycles
“x”: don’t care
Wake-up Times
NotethatiftheWatchdogTimerisdisabled,whichmeansthattheLXTandLIRCareallbothoff,
thentherewillbenoFastWake-upfunctionavailablewhenthedeviceswake-upfromtheSLEEP0
Mode.