Interfacing a Hantronix 320 x 240 Graphics Module to an 8-bit ...

Application NoteCrystal Clear andVisibly Superior LCDModulesInterfacingaHantronix320x240GraphicsModuletoan 8-bitMicrocontrollerIntroduction:Duetoits thinprofile, light weight, lowpowerconsumptionandeasy handling, liquidcrystal graphicdisplay modules areusedinawide varietyof applications. The 320x240 (¼ VGA)LCDdisplay isvery popularinanumberof different computingenvironments. It is forthis reasonthat acontrollerisnot includedonthe module.Possible choices of controllers includeanembedded8-bit microcontrollerwithanLCDcontroller,suchas theEpson/S-MOS SED1335ortheOKI MSM6255/6355. Someembeddedmicrocontrollers, suchasthe NationalNS486SXF, havebuilt-inLCDcontrollers andwill interfacedirectly tothedisplay.ForPCbasedembeddedcontrollers liketheIntel 386/486EX, aVGA controllerchip, suchastheChips andTechnologyF65545 ortheVadem VG-660,isthe bestchoice.Ifthe display is tobe rundirectly from aPC,anumberof VGA cards areavailable that willoperatewith this display. Anumberof singleboardcomputers areavailablewithLCDdisplay outputs.This applicationnotewilldealwithoneof themostpopularapplicationenvironments, the8-bitembeddedmicrocontroller. Theexampledetailedhereis basedonaPhillips87C751microcontrollerdrivinganEpson/S-MOS SED1335LCDcontroller.Functional Description:TheHantronix 320x240seriesof displays haveanindustry standard4-bit parallelinterface. Thisinterfacerequires thecontrollertocontinuously refreshthedisplay andtomaintainthevideodisplay RAM.Beforethedisplaycanbe used themicrocontrollermustfirst sendaseriesof initializationbytes totheLCDcontrollertoset upits operational parameters andtodescribethedisplay tothecontroller.Onceinitializedthe applicationmicrocontrollercansendtext orgraphic datato theLCDcontrollerwhereit willbeformattedandstoredin thedisplay RAM. Coincidentwith theseRAMupdates theLCDcontrolleris continuously readingdatafromthedisplay RAM, serializingit andsendingit tothedisplay. Theapplicationmicrocontrollerdoesn’t havedirectaccess tothedisplayRAM andmust sendall dataand commands totheLCDcontrollerchip.Schematic:The87C751microprocessoris connectedto theLCDcontrollerchipviaparallel I/Oports inthisexample. It couldalso beconnected totheprocessor's databusandbemappedintotheprocessor'sdatamemoryarea. Seefigure1.Page1Copyright2000, Hantronix,Inc.Allrightsreserved

Application NoteCrystal Clear andVisibly Superior LCDModulesSoftwareFlowchart:WRITE ACOMMANDBYTECOMM32:WRITE ADATABYTEWRITE32:MAINPROGRAMLOOPSTART:A0 SETHIGHA0SET LOWINITIALIZESED1335DATATOP1CS=0WRLOWSENDS ABLOCKOFDATATOTHE DISPLAYDATA32:GET BYTEFROMTABLECLEARTEXTPAGEDISPLAYBITMAPDISPLAYTEXTWRHIGHENDBYTE?NOYESRETURNENDCS=1CALLWRITERETURNINC.TABLEPOINTERInitialization:Beforethe LCDcontrollercanaccept ordisplay dataortext it must beinitialized. Thisisusuallydoneimmediatelyafterthesystem is poweredup.Thefollowingchart lists theinitializationcommands and theparameters that accompany them alongwithabrief explanationof thefunctionof each.Page3Copyright2000, Hantronix,Inc.Allrightsreserved

Application NoteInitialization bytes:Crystal Clear andVisibly Superior LCDModulesCOMMAND CODE PARAMETER FUNCTIONSYSTEMSET 40h 30h LCDPANEL HARDWARE SETUP87h CHARACTERWIDTH[7] INPIXELSSCROLLCURSORFORMCURSORDIRECTION44h5dh4ch07h27h39hefh28h000efhb0h04hefh000004h86hCHARACTERHEIGHT[7+1]INPIXELSADDRESS RANGE FOR1TEXTLINELINE LENGTHINCHARACTERS [40-1=39]NUMBEROFLINESPERFRAME [240]HORIZONTALADDRESS RANGE(TEXT)[40]SETS THE SCROLLSTARTADDRESS ANDTHENUMBEROFLINESPERSCROLLBLOCKCURSORFORMANDSIZE [BLOCK,4PIXELS WIDE,6PIXELS HIGH]CURSORDIRECTIONINAUTOWRITE MODE [RIGHT]HORIZONTALSCROLLRATE 5ah 00h HORIZONTALSCROLLRATE, [1] PIXEL ATATIMEOVERLAY 5bh 01h TEXT/GRAPHICS OVERLAY MODE [EXOR]DISPLAY ON/OFF 59h 16h DISPLAY ON/OFF[ON]Displayed image:Page4Copyright2000, Hantronix,Inc.Allrightsreserved

Application NoteCrystal Clear andVisibly Superior LCDModulesdata321:mov r1,alcall write32 ;senditinc dptrsjmp data32 ;nextbyte;CleartextRAMonthe3224clrtext:mov r1,#46h ;setcursorlcall comm32mov dptr,#msg13 ;cursorparamlcall data32mov r1,#42h ;mwritelcall comm32mov dptr,#msg11 ;allspaceslcall data32mov r1,#46h ;setcursorlcall comm32mov dptr,#msg6lcall data32ret;************************************************;TABLESANDDATA;allofwhichare20hmsg11:db ' 'db 01ahmsg18: db 0,01ah ;hscrparam;320x240bonsaitreegraphic;Thefollowingtableisnotlisted;here.Itconsistsof9600bytes;whichconstituteafullscreen;bitmapimageofabonsaitree.;Youmayaddafewbytesbeforethe;01ahterminationbytefortesting;puposesorincludeacomplete;bitmapimagemsg12:msg13:db01ahdb 0,0,01ah ;setcursor;totextpage;Initializationparametersfor3224.msg1:db 30h,87h,07h,27h;systemsetdb 39h,0efh,28h,0h,0a1hmsg2:db 0,0,0efh,0b0h ;scrolldb 04h,0efh,0,0db 0,0,0a1hmsg3:db 04h,86h,0a1h ;csrformmsg4:db 01h,0a1h ;overlayparammsg5:db 16h,0a1h ;dispon/offmsg14:msg15:msg16:msg17:dbdbdbdbdbdbdbdbend'HANTRONIX'0a1h'CrystalClearand'0a1h'VisiblySuperior'0a1h'LCDModules'0a1hmsg6:msg7:msg8:msg9:msg10:db0b0h,04h,0a1h ;setcursorto;graphicspagedb 31h,2h,0a1h ;setcursor;textpage;1stlinedb 59h,2,0a1h ;2ndlinedb 81h,2,0a1h ;3rdlinedb 0a9h,2,0a1h ;4thline;1200spacesfortextpageclear;Thefollowingtableisnotlisted;here,exceptforthefirst8bytes,;butconsistsof1200bytesPage6Copyright2000, Hantronix,Inc.Allrightsreserved