BS85B12-3/BS85C20-3/BS85C20-5
Touch Key Flash MCU with LCD/LED Driver
I/O Pin Structures
TheꢀaccompanyingꢀdiagramsꢀillustrateꢀtheꢀinternalꢀstructuresꢀofꢀsomeꢀgenericꢀI/Oꢀpinꢀtypes.ꢀAsꢀ
theꢀexactꢀlogicalꢀconstructionꢀofꢀtheꢀI/Oꢀpinꢀwillꢀdifferꢀfromꢀtheseꢀdrawings,ꢀtheyꢀareꢀsuppliedꢀasꢀaꢀ
guideꢀonlyꢀtoꢀassistꢀwithꢀtheꢀfunctionalꢀunderstandingꢀofꢀtheꢀI/Oꢀpins.ꢀTheꢀwideꢀrangeꢀofꢀpin-sharedꢀ
structuresꢀdoesꢀnotꢀpermitꢀallꢀtypesꢀtoꢀbeꢀshown.
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Generic Input/Output Structure
Programming Considerations
Withinꢀtheꢀuserꢀprogram,ꢀoneꢀofꢀtheꢀfirstꢀthingsꢀtoꢀconsiderꢀisꢀportꢀinitialisation.ꢀAfterꢀaꢀreset,ꢀallꢀofꢀ
theꢀI/Oꢀdataꢀandꢀportꢀcontrolꢀregisterꢀwillꢀbeꢀsetꢀhigh.ꢀThisꢀmeansꢀthatꢀallꢀI/Oꢀpinsꢀwillꢀdefaultꢀtoꢀ
anꢀinputꢀstate,ꢀtheꢀlevelꢀofꢀwhichꢀdependsꢀonꢀtheꢀotherꢀconnectedꢀcircuitryꢀandꢀwhetherꢀpull-highꢀ
selectionsꢀhaveꢀbeenꢀchosen.ꢀIfꢀtheꢀportꢀcontrolꢀregister,ꢀPAC~PEC,ꢀisꢀthenꢀprogrammedꢀtoꢀsetupꢀ
someꢀpinsꢀasꢀoutputs,ꢀtheseꢀoutputꢀpinsꢀwillꢀhaveꢀanꢀinitialꢀhighꢀoutputꢀvalueꢀunlessꢀtheꢀassociatedꢀ
portꢀdataꢀregister,ꢀPA~PE,ꢀisꢀfirstꢀprogrammed.ꢀSelectingꢀwhichꢀpinsꢀareꢀinputsꢀandꢀwhichꢀareꢀ
outputsꢀcanꢀbeꢀachievedꢀbyte-wideꢀbyꢀloadingꢀtheꢀcorrectꢀvaluesꢀintoꢀtheꢀappropriateꢀportꢀcontrolꢀ
registerꢀorꢀbyꢀprogrammingꢀindividualꢀbitsꢀinꢀtheꢀportꢀcontrolꢀregisterꢀusingꢀtheꢀ"SETꢀ[m].i"ꢀandꢀ
"CLRꢀ[m].i"ꢀinstructions.ꢀNoteꢀthatꢀwhenꢀusingꢀtheseꢀbitꢀcontrolꢀinstructions,ꢀaꢀread-modify-writeꢀ
operationꢀtakesꢀplace.ꢀTheꢀmicrocontrollerꢀmustꢀfirstꢀreadꢀinꢀtheꢀdataꢀonꢀtheꢀentireꢀport,ꢀmodifyꢀitꢀtoꢀ
theꢀrequiredꢀnewꢀbitꢀvaluesꢀandꢀthenꢀrewriteꢀthisꢀdataꢀbackꢀtoꢀtheꢀoutputꢀports.
PortꢀAꢀhasꢀtheꢀadditionalꢀcapabilityꢀofꢀprovidingꢀwake-upꢀfunctions.ꢀWhenꢀtheꢀdeviceꢀisꢀinꢀtheꢀ
SLEEPꢀorꢀIDLEꢀMode,ꢀvariousꢀmethodsꢀareꢀavailableꢀtoꢀwakeꢀtheꢀdeviceꢀup.ꢀOneꢀofꢀtheseꢀisꢀaꢀhighꢀ
toꢀlowꢀtransitionꢀofꢀanyꢀofꢀtheꢀPortꢀAꢀpins.ꢀSingleꢀorꢀmultipleꢀpinsꢀonꢀPortꢀAꢀcanꢀbeꢀsetupꢀtoꢀhaveꢀthisꢀ
function.
Rev. 1.20
66
�ꢀꢁꢀst 10ꢂ 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
