HT45F12
8-Bit Flash MCU with Op Amps & Comparators
Entering the IDLE1 Mode
ThereꢀisꢀonlyꢀoneꢀwayꢀforꢀtheꢀdeviceꢀtoꢀenterꢀtheꢀIDLE1ꢀModeꢀandꢀthatꢀisꢀtoꢀexecuteꢀtheꢀ“HALT”ꢀ
instructionꢀinꢀtheꢀapplicationꢀprogramꢀwithꢀtheꢀIDLENꢀbitꢀinꢀSYSMODꢀregisterꢀequalꢀtoꢀ“1”ꢀandꢀtheꢀ
FSYSONꢀbitꢀinꢀCTRLꢀregisterꢀequalꢀtoꢀ“1”.ꢀWhenꢀthisꢀinstructionꢀisꢀexecutedꢀunderꢀtheꢀconditionsꢀ
describedꢀabove,ꢀtheꢀfollowingꢀwillꢀoccur:
•ꢀ TheꢀsystemꢀclockꢀandꢀTimeꢀBaseꢀclockꢀandꢀfSUBꢀclockꢀwillꢀbeꢀonꢀandꢀtheꢀapplicationꢀprogramꢀwillꢀ
stopꢀatꢀtheꢀ“HALT”ꢀinstruction
•ꢀ TheꢀDataꢀMemoryꢀcontentsꢀandꢀregistersꢀwillꢀmaintainꢀtheirꢀpresentꢀcondition.
•ꢀ TheꢀWDTꢀwillꢀbeꢀclearedꢀandꢀresumeꢀcountingꢀifꢀtheꢀWDTꢀisꢀenabledꢀregardlessꢀofꢀtheꢀWDTꢀ
clockꢀsourceꢀwhichꢀoriginatesꢀfromꢀtheꢀfLꢀclock
•ꢀ TheꢀI/Oꢀportsꢀwillꢀmaintainꢀtheirꢀpresentꢀconditions.
•ꢀ Inꢀtheꢀstatusꢀregister,ꢀtheꢀPowerꢀDownꢀflag,ꢀPDF,ꢀwillꢀbeꢀsetꢀandꢀtheꢀWatchdogꢀtime-outꢀflag,ꢀTO,ꢀ
willꢀbeꢀcleared.
Standby Current Considerations
AsꢀtheꢀmainꢀreasonꢀforꢀenteringꢀtheꢀSLEEPꢀorꢀIDLEꢀModeꢀisꢀtoꢀkeepꢀtheꢀcurrentꢀconsumptionꢀofꢀtheꢀ
deviceꢀtoꢀasꢀlowꢀaꢀvalueꢀasꢀpossible,ꢀperhapsꢀonlyꢀinꢀtheꢀorderꢀofꢀseveralꢀmicro-ampsꢀexceptꢀinꢀtheꢀ
IDLE1ꢀMode,ꢀthereꢀareꢀotherꢀconsiderationsꢀwhichꢀmustꢀalsoꢀbeꢀtakenꢀintoꢀaccountꢀbyꢀtheꢀcircuitꢀ
designerꢀifꢀtheꢀpowerꢀconsumptionꢀisꢀtoꢀbeꢀminimised.ꢀSpecialꢀattentionꢀmustꢀbeꢀmadeꢀtoꢀtheꢀI/Oꢀpinsꢀ
onꢀtheꢀdevice.ꢀAllꢀhigh-impedanceꢀinputꢀpinsꢀmustꢀbeꢀconnectedꢀtoꢀeitherꢀaꢀfixedꢀhighꢀorꢀlowꢀlevelꢀasꢀ
anyꢀfloatingꢀinputꢀpinsꢀcouldꢀcreateꢀinternalꢀoscillationsꢀandꢀresultꢀinꢀincreasedꢀcurrentꢀconsumption.ꢀ
Thisꢀalsoꢀappliesꢀtoꢀdeviceꢀwhichꢀhasꢀdifferentꢀpackageꢀtypes,ꢀasꢀthereꢀmayꢀbeꢀunbondedꢀpins.ꢀTheseꢀ
mustꢀeitherꢀbeꢀsetupꢀasꢀoutputsꢀorꢀifꢀsetupꢀasꢀinputsꢀmustꢀhaveꢀpull-highꢀresistorsꢀconnected.ꢀ
Careꢀmustꢀalsoꢀbeꢀtakenꢀwithꢀtheꢀloads,ꢀwhichꢀareꢀconnectedꢀtoꢀI/Oꢀpins,ꢀwhichꢀareꢀsetupꢀasꢀoutputs.ꢀ
Theseꢀshouldꢀbeꢀplacedꢀinꢀaꢀconditionꢀinꢀwhichꢀminimumꢀcurrentꢀisꢀdrawnꢀorꢀconnectedꢀonlyꢀtoꢀ
externalꢀcircuitsꢀthatꢀdoꢀnotꢀdrawꢀcurrent,ꢀsuchꢀasꢀotherꢀCMOSꢀinputs.ꢀAlsoꢀnoteꢀthatꢀadditionalꢀ
standbyꢀcurrentꢀwillꢀalsoꢀbeꢀrequiredꢀifꢀtheꢀconfigurationꢀoptionsꢀhaveꢀenabledꢀtheꢀLIRCꢀoscillator.
InꢀtheꢀIDLE1ꢀModeꢀtheꢀsystemꢀoscillatorꢀisꢀon,ꢀifꢀtheꢀsystemꢀoscillatorꢀisꢀfromꢀtheꢀhighꢀspeedꢀsystemꢀ
oscillator,ꢀtheꢀadditionalꢀstandbyꢀcurrentꢀwillꢀalsoꢀbeꢀperhapsꢀinꢀtheꢀorderꢀofꢀseveralꢀhundredꢀmicro-
amps.
Wake-up
AfterꢀtheꢀsystemꢀentersꢀtheꢀSLEEPꢀorꢀIDLEꢀMode,ꢀitꢀcanꢀbeꢀwokenꢀupꢀfromꢀoneꢀofꢀvariousꢀsourcesꢀ
listedꢀasꢀfollows:
•ꢀ Anꢀexternalꢀreset
•ꢀ AnꢀexternalꢀfallingꢀedgeꢀonꢀPortꢀA
•ꢀ Aꢀsystemꢀinterrupt
•ꢀ AꢀWDTꢀoverflow
Ifꢀtheꢀsystemꢀisꢀwokenꢀupꢀbyꢀanꢀexternalꢀreset,ꢀtheꢀdeviceꢀwillꢀexperienceꢀaꢀfullꢀsystemꢀreset,ꢀ
however,ꢀifꢀtheꢀdeviceꢀisꢀwokenꢀupꢀbyꢀaꢀWDTꢀoverflow,ꢀaꢀWatchdogꢀTimerꢀresetꢀwillꢀbeꢀinitiated.ꢀ
Althoughꢀbothꢀofꢀtheseꢀwake-upꢀmethodsꢀwillꢀinitiateꢀaꢀresetꢀoperation,ꢀtheꢀactualꢀsourceꢀofꢀtheꢀ
wake-upꢀcanꢀbeꢀdeterminedꢀbyꢀexaminingꢀtheꢀTOꢀandꢀPDFꢀflags.ꢀTheꢀPDFꢀflagꢀisꢀclearedꢀbyꢀaꢀ
systemꢀpower-upꢀorꢀexecutingꢀtheꢀclearꢀWatchdogꢀTimerꢀinstructionsꢀandꢀisꢀsetꢀwhenꢀexecutingꢀtheꢀ
“HALT”ꢀinstruction.ꢀTheꢀTOꢀflagꢀisꢀsetꢀifꢀaꢀWDTꢀtime-outꢀoccurs,ꢀandꢀcausesꢀaꢀwake-upꢀthatꢀonlyꢀ
resetsꢀtheꢀProgramꢀCounterꢀandꢀStackꢀPointer,ꢀtheꢀotherꢀflagsꢀremainꢀinꢀtheirꢀoriginalꢀstatus.
Rev. 0.00
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�eꢀteꢁꢂeꢃ ꢄꢅꢆ ꢄ01ꢄ
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
