Holtek BS82B12A-3 - Ente�Ing the IDLE0 Mode

Rev. 1.20 54 January 23, 2015 Rev. 1.20 55 January 23, 2015
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
Entering the IDLE0 Mode
ThereisonlyonewayforthedevicestoentertheIDLE0Modeandthatistoexecutethe"HALT"
instructionintheapplicationprogramwiththeIDLENbitinSMODregisterequalto"1"andthe
FSYSONbitinCTRLregisterequalto"0".Whenthisinstructionisexecutedundertheconditions
describedabove,thefollowingwilloccur:
• Thesystemclockwillbestoppedandtheapplicationprogramwillstopatthe"HALT"instruc-
tion,butthelowfrequencyf
SUB
clockwillbeon.
• TheDataMemorycontentsandregisterswillmaintaintheirpresentcondition.
• TheWDTwillbeclearedandresumecounting.
• TheI/Oportswillmaintaintheirpresentconditions.
• Inthestatusregister,thePowerDownag,PDF,willbesetandtheWatchdogtime-outag,TO,
willbecleared.
Entering the IDLE1 Mode
ThereisonlyonewayforthedevicestoentertheIDLE1Modeandthatistoexecutethe"HALT"
instructionintheapplicationprogramwiththeIDLENbitinSMODregisterequalto"1"andthe
FSYSONbitinCTRLregisterequalto"1".Whenthisinstructionisexecutedundertheconditions
describedabove,thefollowingwilloccur:
• Thesystemclockandthelowfrequencyf
SUB
willbeonandtheapplicationprogramwillstopat
the"HALT"instruction.
• TheDataMemorycontentsandregisterswillmaintaintheirpresentcondition.
• TheWDTwillbeclearedandresumecounting.
• TheI/Oportswillmaintaintheirpresentconditions.
• Inthestatusregister,thePowerDownag,PDF,willbesetandtheWatchdogtime-outag,TO,
willbecleared.
Standby Current Considerations
AsthemainreasonforenteringtheSLEEPorIDLEModeistokeepthecurrentconsumptionof
thedevicestoaslowavalueaspossible,perhapsonlyintheorderofseveralmicro-ampsexcept
intheIDLE1Mode,thereareotherconsiderationswhichmustalsobetakenintoaccountbythe
circuitdesignerifthepowerconsumptionistobeminimised.Specialattentionmustbemadeto
theI/Opinsonthedevice.Allhigh-impedanceinputpinsmustbeconnectedtoeitheraxedhigh
orlowlevelasanyfloatinginputpinscouldcreateinternaloscillationsandresultinincreased
currentconsumption.Thisalsoappliestodeviceswhichhavedifferentpackagetypes,astheremay
beunbonbedpins.Thesemusteitherbesetupasoutputsorifsetupasinputsmusthavepull-high
resistorsconnected.
Caremustalsobetakenwiththeloads,whichareconnectedtoI/Opins,whicharesetupas
outputs.Theseshouldbeplacedinaconditioninwhichminimumcurrentisdrawnorconnected
onlytoexternalcircuitsthatdonotdrawcurrent,suchasotherCMOSinputs.IntheIDLE1Mode
thesystemoscillatorison,ifthesystemoscillatorisfromthehighspeedsystemoscillator,the
additionalstandbycurrentwillalsobeperhapsintheorderofseveralhundredmicro-amps.