ST2202A
7.4 RAM
InternalꢀstaticꢀRAMꢀcanꢀbeꢀdividedꢀintoꢀ3ꢀpartsꢀinꢀfunction.ꢀFirstꢀ
isꢀtheꢀzeroꢀpageꢀmemory,ꢀsecondꢀisꢀforꢀstack,ꢀandꢀthirdꢀcanꢀbeꢀ
usedꢀasꢀLCDꢀframeꢀbufferꢀorꢀforꢀgeneralꢀpurpose.ꢀ ꢀ
ꢀ
stackꢀpointerꢀcarefully,ꢀstackꢀmemoryꢀcanꢀalsoꢀbeꢀusedꢀasꢀdataꢀ
memory.ꢀ
ꢀ
ꢀ
User Memory and LCD Frame Buffer
($0200~$0FFF)
ꢀ
Zero Page Data RAM ($0080~$00FF)
Totalꢀ128ꢀbytesꢀofꢀdataꢀRAMꢀinꢀzeroꢀpageꢀisꢀveryꢀusefulꢀforꢀ
programmers.ꢀTheyꢀprovideꢀshortꢀinstructionꢀcodesꢀandꢀcycles.ꢀ
Useꢀzeroꢀpageꢀaddressingꢀmodeꢀonꢀtheꢀvariablesꢀinꢀthisꢀareaꢀ
usuallyꢀspeedsꢀupꢀtheꢀoverallꢀperformance.ꢀ
ꢀ
TheꢀST2202ꢀsharesꢀmemoryꢀforꢀbothꢀuserꢀmemoryꢀandꢀLCDꢀ
frameꢀbuffer.ꢀTheꢀrangeꢀofꢀLCDꢀframeꢀbufferꢀwillꢀbeꢀfixedꢀafterꢀ
initializationꢀofꢀLCDꢀcontrolꢀregisters.ꢀMemoryꢀbeyondꢀisꢀuserꢀ
memory.ꢀReadꢀandꢀwriteꢀoperationsꢀcanꢀbeꢀappliedꢀtoꢀLCDꢀ
frameꢀbufferꢀtoꢀmaintainꢀdisplayꢀcontent,ꢀandꢀalmostꢀnoneꢀofꢀ
theꢀCPUꢀtimeꢀisꢀaffected.ꢀThisꢀisꢀcontributedꢀbyꢀoneꢀspecialꢀ
memoryꢀtransferꢀtechniqueꢀofꢀdisplayꢀdataꢀfromꢀLCDꢀframeꢀ
bufferꢀtoꢀtheꢀLCDꢀcontroller.
ꢀ
Stack RAM ($0100~$01FF)
TheꢀST2202ꢀhasꢀ256ꢀbytesꢀstackꢀfromꢀ$0100ꢀtoꢀ$01FF.ꢀItꢀ
providesꢀaꢀmaximumꢀofꢀ128ꢀlevelsꢀforꢀsubroutines.ꢀByꢀsettingꢀ
Verꢀ2.5ꢀ
11
/75
ꢀ
9/16/2008ꢀ
SITRONIX [ SITRONIX TECHNOLOGY CO., LTD. ]
