BS85B12-3/BS85C20-3/BS85C20-5
Touch Key Flash MCU with LCD/LED Driver
Wake-up
AfterꢀtheꢀsystemꢀentersꢀtheꢀSLEEPꢀorꢀIDLEꢀMode,ꢀitꢀcanꢀbeꢀwokenꢀupꢀfromꢀoneꢀofꢀvariousꢀsourcesꢀ
listedꢀasꢀfollows:
•ꢀ Anꢀexternalꢀreset
•ꢀ AnꢀexternalꢀfallingꢀedgeꢀonꢀPortꢀA
•ꢀ Aꢀsystemꢀinterrupt
•ꢀ AꢀWDTꢀoverflow
Ifꢀtheꢀsystemꢀisꢀwokenꢀupꢀbyꢀanꢀexternalꢀreset,ꢀtheꢀdeviceꢀwillꢀexperienceꢀaꢀfullꢀsystemꢀreset,ꢀ
however,ꢀifꢀtheꢀdeviceꢀisꢀwokenꢀupꢀbyꢀaꢀWDTꢀoverflow,ꢀaꢀWatchdogꢀTimerꢀresetꢀwillꢀbeꢀinitiated.ꢀ
Althoughꢀbothꢀofꢀtheseꢀwake-upꢀmethodsꢀwillꢀinitiateꢀaꢀresetꢀoperation,ꢀtheꢀactualꢀsourceꢀofꢀtheꢀ
wake-upꢀcanꢀbeꢀdeterminedꢀbyꢀexaminingꢀtheꢀTOꢀandꢀPDFꢀflags.ꢀTheꢀPDFꢀflagꢀisꢀclearedꢀbyꢀaꢀ
systemꢀpower-upꢀorꢀexecutingꢀtheꢀclearꢀWatchdogꢀTimerꢀinstructionsꢀandꢀisꢀsetꢀwhenꢀexecutingꢀ
theꢀ"HALT"ꢀinstruction.ꢀTheꢀTOꢀflagꢀisꢀsetꢀifꢀaꢀWDTꢀtime-outꢀoccurs,ꢀandꢀcausesꢀaꢀwake-upꢀthatꢀonlyꢀ
resetsꢀtheꢀProgramꢀCounterꢀandꢀStackꢀPointer,ꢀtheꢀotherꢀflagsꢀremainꢀinꢀtheirꢀoriginalꢀstatus.
EachꢀpinꢀonꢀPortꢀAꢀcanꢀbeꢀsetupꢀusingꢀtheꢀPAWUꢀregisterꢀtoꢀpermitꢀaꢀnegativeꢀtransitionꢀonꢀtheꢀpinꢀ
toꢀwake-upꢀtheꢀsystem.ꢀWhenꢀaꢀPortꢀAꢀpinꢀwake-upꢀoccurs,ꢀtheꢀprogramꢀwillꢀresumeꢀexecutionꢀatꢀ
theꢀinstructionꢀfollowingꢀtheꢀ"HALT"ꢀinstruction.ꢀIfꢀtheꢀsystemꢀisꢀwokenꢀupꢀbyꢀanꢀinterrupt,ꢀthenꢀ
twoꢀpossibleꢀsituationsꢀmayꢀoccur.ꢀTheꢀfirstꢀisꢀwhereꢀtheꢀrelatedꢀinterruptꢀisꢀdisabledꢀorꢀtheꢀinterruptꢀ
isꢀenabledꢀbutꢀtheꢀstackꢀisꢀfull,ꢀinꢀwhichꢀcaseꢀtheꢀprogramꢀwillꢀresumeꢀexecutionꢀatꢀtheꢀinstructionꢀ
followingꢀtheꢀ"HALT"ꢀinstruction.ꢀInꢀthisꢀsituation,ꢀtheꢀinterruptꢀwhichꢀwoke-upꢀtheꢀdeviceꢀwillꢀnotꢀbeꢀ
immediatelyꢀserviced,ꢀbutꢀwillꢀratherꢀbeꢀservicedꢀlaterꢀwhenꢀtheꢀrelatedꢀinterruptꢀisꢀfinallyꢀenabledꢀorꢀ
whenꢀaꢀstackꢀlevelꢀbecomesꢀfree.ꢀTheꢀotherꢀsituationꢀisꢀwhereꢀtheꢀrelatedꢀinterruptꢀisꢀenabledꢀandꢀtheꢀ
stackꢀisꢀnotꢀfull,ꢀinꢀwhichꢀcaseꢀtheꢀregularꢀinterruptꢀresponseꢀtakesꢀplace.ꢀIfꢀanꢀinterruptꢀrequestꢀflagꢀisꢀ
setꢀhighꢀbeforeꢀenteringꢀtheꢀSLEEPꢀorꢀIDLEꢀMode,ꢀtheꢀwake-upꢀfunctionꢀofꢀtheꢀrelatedꢀinterruptꢀwillꢀ
beꢀdisabled.
System
Oscillator
Wake-up Time
(SLEEP Mode)
Wake-up Time
(IDLE0 Mode)
Wake-up Time
(IDLE1 Mode)
HIRC
LIRC
15~16 HIRC cycles
1~2 HIRC cycles
1~2 LIRC cycles
1~2 LIRC cycles
Wake-Up Times
Programming Considerations
TheꢀhighꢀspeedꢀandꢀlowꢀspeedꢀoscillatorsꢀbothꢀuseꢀtheꢀsameꢀSSTꢀcounter.ꢀForꢀexample,ꢀifꢀtheꢀsystemꢀ
isꢀwokenꢀupꢀfromꢀtheꢀSLEEPꢀModeꢀtheꢀHIRCꢀoscillatorꢀneedsꢀtoꢀstart-upꢀfromꢀanꢀoffꢀstate.
•ꢀ IfꢀtheꢀdeviceꢀisꢀwokenꢀupꢀfromꢀtheꢀSLEEPꢀModeꢀtoꢀtheꢀNORMALꢀMode,ꢀtheꢀhighꢀspeedꢀsystemꢀ
oscillatorꢀneedsꢀanꢀSSTꢀperiod.ꢀTheꢀdeviceꢀwillꢀexecuteꢀtheꢀfirstꢀinstructionꢀafterꢀHTOꢀisꢀhigh.
Rev. 1.20
51
�ꢀꢁꢀst 10ꢂ 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
