Inside Macintosh Hardware

^ I.{ACIMOSB USER EDUCATION I.IIE I,IACIIIITOSH BARDI{ARE Uodtflcatlon Bletory: \. /IIARDT{ARE/NOM Flrst Draft Chrls Eeplnoea & Nlck Turuer 214185 Second Draft Brlao Eoward 2l L3l 85 2 llaclntosh Hardware TABLE OF CONTENTS 3 o n D n n n n n n n B n n n n n n n D n D D n n n About Thle Chapter Ovenrlew of the Bardware The Vldeo Interface The Sound Geuerator Dlagram The SCC DLagran The Houae Dlagrau The Keyboard aod Keypad Keyboard Conrnunlcatton Protocol Keypad Coonunlcatloo Protocol The Dlsk Interface Controlllng the Dlsk-State Control Llnes Readtng the Dlek Reglsters I{rltlng to the Dlsk Regletero Exptanatlous of the Dlek Regleters The Real-Tlne Clock Acceeslng the Clock Chlp The One-Second Interrupt The VIA VIA Reglater A VIA Reglster B The VIA Perlpheral Control Regleter The VIA Tlners D VIA Interrupte Other VIA Reglstere Systen Startup n Sunnnary D \-/ T v Copyrlght (c) f 985 Apple Couputer, Iac. All rlghte reeened. Dlstrlbutlon of thls draft ln llulted quantttles does uot conetltute publlcat lon. \-/ ABOUT TEIS CHAPTER 3 ABOUT TTIIS CtsAPTER Ttrlg chapter provldea a baatc deecrtptlon of the hardsare of the Ilactntoeh t28K and 5t2K couputere. It gtvea you tnforuatton thrt yourll need to connect other devtces to the llactntogh and to rllte devlce drtvere or other lorlcvel prograne. It r11I hclp you f lgure out wtrtch technlcal docuoente yourll need to deelgn perlpheralr; ln some cases, your1l have to obtaln detallcd apeclftctttoas froo the uanufacturera of the varloue taterface chlpa. Thte chapter 1e ortented tosard aaaeubly-language Progra@€!8r It assuoee youfre faolltar wlth the baelc operetlon of ntcroprocetaor based devlcee. Knowledge of the }lactntogh Operattng Syeteo w111 algo be he1pful. (warnlng) 0n1y the ltaclntoeh 128K and 512K 8re covered tn thle chapter. In perttcular, Dote that the neuory addreeeee and Bcreen elze are dlfferent on the Uaclntoeh XL (and Bay be dtfferent lu future verelons of the llaclntoeh). To nalntaln software coupattbtllty ecroes the ltaclntoeh 1lne, aod to allow for future changes to the hardware, you're ctrongly advlred to uee the Toolbox and Operatlng Syeten routlnes wherever posslble. To learn how your Prograe c8n deterulne rhlch hardsare eovlronment lt r e operatlng ln, Bee the descriptlon of the Eovtrons procedure ln the Operattng Syeteo Utllltlee chapter. OVERVIEI{ OF TUE EARDI{ARE The l{actntosh conputer contalos a Hotorola }tC68005 rlcroproceaaor clocLed at 7.8336 negahertz, random accesa lDenory (RAn), read-only Eenory (nOu) , and eeveral chlps that enable lt to cornuntcete slth exterual devtcee. There ere flve I-l0 devlcee: the vtdeo dteplay; the sound generator; a Synertek SY6522 Versattle loterface Adapter (VIA) for the Eouse and keyboard; a ZLLog 28530 Serlal Connruntcatlona Controller (SCC) for serlal comualcatlon; and an App1e cuetm chtp, called the II{}t (t'Integrated lfoz Hachlne") for dlsk control. The llaclntoeh uaes Demory'{ePPed I,l0, shtch Eeane that…