Holtek HT66F0175 - System Operation Modes

Rev. 1.50 46 August 28, 2017 Rev. 1.50 47 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
System Operation Modes
Therearesixdifferentmodesofoperationforthemicrocontroller,eachonewithitsown
specialcharacteristicsandwhichcanbechosenaccordingtothespecificperformanceand
powerrequirementsoftheapplication.Therearetwomodesallowingnormaloperationofthe
microcontroller,theNORMALModeandSLOWMode.Theremainingfourmodes,theSLEEP0,
SLEEP1,IDLE0andIDLE1Mode,areusedwhenthemicrocontrollerCPUisswitchedoffto
conservepower.
Operation Mode
Description
CPU f
SYS
f
SUB
f
TBC
NORMAL On f
H
~f
H
/64 On On
SLOW On f
SUB
On On
IDLE0 Off Off On On
IDLE1 Off On On On
SLEEP0 Off Off Off Off
SLEEP1 Off Off On Off
NORMAL Mode
Asthenamesuggeststhisisoneofthemainoperatingmodeswherethemicrocontrollerhasallof
itsfunctionsoperationalandwherethesystemclockisprovidedbyoneofthehighspeedoscillators.
Thismodeoperatesallowingthemicrocontrollertooperatenormallywithaclocksourcewillcome
fromoneofthehighspeedoscillators,eithertheHXTorHIRCoscillators.Thehighspeedoscillator
willhoweverrstbedividedbyaratiorangingfrom1to64,theactualratiobeingselectedbythe
CKS2~CKS0andHLCLKbitsintheSMODregister.Althoughahighspeedoscillatorisused,
runningthemicrocontrolleratadividedclockratioreducestheoperatingcurrent.
SLOW Mode
Thisisalsoamodewherethemicrocontrolleroperatesnormallyalthoughnowwithaslowerspeed
clocksource.Theclocksourceusedwillbefromoneofthelowspeedoscillators,eithertheLXT
ortheLIRC.Runningthemicrocontrollerinthismodeallowsittorunwithmuchloweroperating
currents.IntheSLOWMode,thef
H
isoff.
SLEEP0 Mode
TheSLEEP0ModeisenteredwhenanHALTinstructionisexecutedandwhentheIDLENbitin
theSMODregisterislow.IntheSLEEP0modetheCPUwillbestopped,thef
SUB
clockwillalsobe
stoppedandtheWatchdogTimerfunctionisdisabled.Inthismode,theLVDENmustbesetto“0”.
IftheLVDENissetto“1”,itwon’tentertheSLEEP0Mode.
SLEEP1 Mode
TheSLEEP1ModeisenteredwhenanHALTinstructionisexecutedandwhentheIDLENbitinthe
SMODregisterislow.IntheSLEEP1modetheCPUwillbestopped.Howeverthef
SUB
clockwill
continuetooperateiftheWatchdogTimerfunctionisenabled.
IDLE0 Mode
TheIDLE0ModeisenteredwhenaHALTinstructionisexecutedandwhentheIDLENbitinthe
SMODregisterishighandtheFSYSONbitintheCTRLregisterislow.IntheIDLE0Modethe
systemoscillatorwillbeinhibitedfromdrivingtheCPUbutsomeperipheralfunctionswillremain
operationalsuchastheWatchdogTimerandTMs.IntheIDLE0Mode,thesystemoscillatorwillbe
stopped.