Atari 800 Operating System Manual, Part 1 Of 4

AllARl%oo/8oo ATARI HOME COMPUTERSYSTEM

TECHN ICAL REFERENC NE OTES includes:

OperatingSystemUser'sManual OperatingSystemSourceListing and HardwareManual

TO ALL PTRSONS RECTIVINCfHIS DOCUMTNT Reproductionis forbidden without lhe specificwritten permissionof ATARI,lN(. Sunnr\ale,(A q408b.No risht to reprodu(elhi\ do(umenr, nor the.ubie(l m.tllerlhereof,i. Brantedunles\br $ri en rgreement$ith, or rvritlenpermissionfrom the CorDoration.

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" ATAR| ^-","", ".-**--.c.*-!o

ATARI%oo/8oo ATARI"HOME COMPUTERSYSTEM

OPERATING SYSTEM MANUAL USER'S

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ATARI'. -"^. --^--,-.-*-, s

C O P Y R T G H T1 9 8 2 , A T A R I , I N C . ALL RIGHTS RESERVED

IO ATT PERSONS RECEIVINC THIS DOCUMENf Reproduclion is forbidden without the specific written permission of ATARI,lNC. Sunnyva'e, CA 94086.No rightto reproduc€this documenl, nor the subiectmatter thereof, is grantedunlessby written agreem€nrwilh, or wrillen oermission from the CorDoration.

Every efforl: has been made to ensure that this manual accurately alocuments this product of the ATARI Hoine Computer Division. Ho$rever, due to the ongoing improvement anal update of the computer software and hardware, ATARI, IllC. cannot guarantee the accuracy of printed rnaterial after the date of publication and disclains 'o-r changes, errors, or omissionsliability

ATARI Ho e Cofip uter Opereting Sgsten USER'S MANUAL

PREFACE

17

INTRODUCTION

1A

CENERAL DESCRIPTION OF THE ATARI COI'IPUTERSYSTEM

1A

CooventionE U6ed in ThiE Manoel HEXADECII4AL NUMBERS MEI.IORYADDRESSES KILOBYTES OF IIEIIORY FASCAL AS AN ALGORITHM-SPECIFICATIAN LANGUAC€ MSI,IORYLAVOUTS BACKUS-NAURFORM (BNF) OS-EOUATE F ILSNAI.IES

20 20 20

OFERATINC SYSTEM FUNCTIONALORGANIZATION I n p u t l o { . r t p u t S u bs q s t e o Interr"upt Froc es6 ing Initirl i.ation

22 23

Pouer-Up Srts tett| R€9€ t FI oat ing Point A"ithmetic

Pa.kage

24

CONFIGURAIIONS

2e

Progran Envi r onfientE

23

Blac kboard flode Caitr idge Diskette-Boot C a 6s e t t e - 8 o o t

29

R A M E xp a n 6 i o n P e r 'i p h e r a 1 D e v i c e E

27

eane Controt 1erg Progra{r R€coider Ser ia I B|,E DevicaE SYSTEI.I I'IEHORYUI ILI ZAT ION

29

RAHRegion

e9

Pege O Page 1 OS D€ta 8es€ UEer l.lortspate Boot.8€9ion S.reen Displag Li6t F r e € l { e m o r g R e gi o n

4

2A

30 30 30 and Data

31 31

C a rt r i d g e s A a n d g l'lapped I/O Re6ident OS and Floating Point Packag€ Centia 1 Data BeEe DeEc.iption l,le{florq Dgnafii c a P r o Ee 6 E Sgrtem Initializetion C h a n gi n g S c r e e n I ' l o d € s I,/O SUBSYSTET'I Central I/O Utilitg C I 0 D e 5i 9 n P h i t o s o p h q DEVICE INDEPENDENCE DATA ACCESS I'IETHODS I'IULTIPLE DEVICE/FILE CONCURRENCY UNIFIED ERRAR HANDLINE DEVICE EXPANSION CIO CALLINE MECHANISM HANDLER ID -- ICHID [O34O] DEVICE NUMBER_- ICDNO tO341] COMI.IAND BYTE __ ICCMD TO342] -STATUS ICSTA to343l SUFFER ADDRESS ICBALT0344] AND ICBAH IO3451 PUT ADDRESS -ICPTL T0346] AND ICPTH tO347] EUFFER LENGTH/BYTE COUNI -ICBLL to34gl and ICBLH CO349l AUXILIARY INFARi.IATION-ICAXl tO34Al and ICAX2 lO34gl REI4AININC BYTES ( ICAX3- ICAX6 }

39 40 40

40 40 40 4L

C I O F u n ct i o n 5

4L

OpEN --

AEEign DeviEe/Filename to IOCB €nd Readq fot'Acces6 CLoSF -- Terminat€ AccesF to Device/Fi1e and Rel eas6 IOCB OFT CHARACTER9-- Read n Cha.ertarg (B{ te-AI i gned Aec€ss} PUT CHARAC1ERS-- wr.ite n Cha.Ect6rs ( B gt e - A I i g n e d A t c € s E ) e E T R E C O R D- - R e a d U D T o n C h a r € c t € r 6 ( R e e o r d - A l i g n e d A c E e E s) P U T R E C O R D- - t 0 r . i t e U p T o n c h E r a e t e r e ( R e c o . d - A I i g n e d A c c e s s) G E T S T A T U S- - R e t u r n D e v i t e - D e p e n d e n t S t a t u E B gt € € SPECIAL -- 9Decial Function

41 42

43 44 44 45 45

Device/Fi lenene gpecif ication I/O Eraftple

46 47

D e v i c e S p e ci f i . I n + o r r n a t i o n K e q b o a r d H a n dI e r .

50 90

CIO Function Descriotiong

51

T h 6 o . g o f O pe r a t i o n

51

D i E p1 a g H € n d l e r ( S : ) Scaoan llodes TEXT HADE O TEXT }'1ODES1 AND 2 eRAPHICS ODES (Modei 3 Thiough 111 SPLIT*SCREEN CONFIOURATIONS C I O F u n ct i o n D e s e r . i t t i o n 6 User-AIterab 1e DEte Base Variables Theor! of Operation licreen Editor

(E: )

CIO Fun.t ion DeEcrirtiong User-Al terab 1e Data Base Var'i€bIes C a e E e t t e H a n d1 e " ( C : ) C I O F u n ct i o n D e s E r i p t i o n 6 T h e o r g o f O pe r a t i o n Fi 1e Str uctuf e

54 54

61

66

70

Pr inter Handler (F: ) CIO Flnction DeEctiptiong T he o r g o f O p e r € t i o n DiE|( File

Hanager (D: )

CI0 Flnction oescriptionE D € v i c e / F i 1 e n € f i e S p e ci + i E E t i o n

7e 79

al

Fi lenane tli ldcard ing S p e ci a l C I O f u n c t i o n 5 l h e o r g o f O pe r a t i o n F l ' l SD i s k e t t e U t i l i r € t i o n FMS BOOT RECORD FORI'IAT BOOT PROCESS I'IEI.IORYIIAP VALU''IE TABLE OF CONTENTS FILE DIRECTORYFORT4AT FIIS FILE SECTOR FORI'IAT Non-CIO I/0 R e si d e n t D e v i € e H a n dl e r

a9 90 s2 94 99

Vectorg

R e s i d e n t D i s f t € t t e H a n dI e i D i e k e t t € H.nd ler Co|llmand 9 Ser ia 1 BUE l/o

97 99 101

INTERRUPT PRACESSING

102

C h i p - R e Fe t N o n o e E * e bl e

103

Intarrupts

S t a g e 1 V S L A N KP r o c e E s S t a g e 2 V B L A N I 4P i o c e E i H a sk e b l e I n t e r r u p t E Interrupt Initislirstion givstem T ioers Usage Not€9 PoKEY Interiup t i'{ei k S€tting Interrupt and Timer Vector.E gteck Content 3t Interrupt Vector. PointE llisce I laneous ConBiderations FlorrchaitE

1C4

10e 109 109 110 110 111 LLz 113

SYSTEI'I INI TIALI ZATIAN

r16

Pouer-Uplnitialiration(Coldstart)pr.oceduie (lrar.nstart) procedore SgEteo Reset tniti€liz€tion

116 119

FLOATING POINT ARITHI,IETTCPACKAGE Funrtions/Cal

lin9

Sequence6

ASCII to Flodting Point Conversion (AFpt Floating Point to AgCII Conve.sion (FASC) InteEer to Floating Point Conv€teion (IFp) Floating Point to Integei Conversion (FpIt Float ing Point Addltion (FADD' Flo.t ing Point Subtr.action (FSUBI (Fl.lULt F106ting Point Multiplic6tion ( F D M Fl oat ing Point Division Floating Point Loga.ithms (LOe end LOOTO' Floeting Point Etponentiation (EXp end EXpIO' (pLyEVL' Floating Point Polrrnonial Eveluation ( Cleer FRO ZFRO) C1e€i Pege-Z6ro Floetinq Folnt Number (ZF1) L o a d F l o a t i n g P o i f l t N u r D b e rt o F R O ( FLDOR and FLDOP) Losd Flo6tlng Point Nuftber to FR1 ( F L D l R a n d F L D 1 P) Stora Floatinq Point Number Fnor FRO ( FATOR and FSTOP) ove Floating Point Numbsr From FRO to FRl

( Ft'tovEt

123 r23 124 124 t23

127

1eE

Resour'6. Uti I i z.tion Iop l€fientati on Det€i 1s

t??

ADDING NEI.' DEVICE HANDLERS./PER TPHERALS

131

Oevice T€ble CI t l / H € n d l e i l n t 6 . * a c e

134 134

Calling lvlechaniEtn Hendlei. Initialitstion Fsnction6 Suppoited E r F o r H a n dI i n g Rdsourca Al location ZERO-PACE RA}I NONZERO_PAOERAH STACK SPACE H a n dt .e . , / S I O I n t e a f a c e

135 736 140 140

t4r. 141 142

142 L44 L44

Calling MechEnisdr F u n E t i o n 6 S u pp o f t e d Er.r.or Handl ing SEr'ial I/o

8us Chsr€ctefistics

End Protocol

H a r d u a r e / E l e ct r ' i c a I C h e r € c t e r i s t i c s Specificetions Seria I Poit Electrical Bus Comanandg COI'II,IANDFRAI'IE COMhANDFRAI'TEACKNT]WLEDOE DATA FRAI'IE OPERATIONCOMPLETE

10

145 145 147 147 144 148 t49 149

Bu6 T ining

150

H e n d1 s r E n v i r o n m e n t

192

B o o t a b 1 e H € n d1 e r C a r t r i d g e R e si d e n t H a n d1 e r FlolrEh€r'tE

193 153 153

PROCRAI{ENVIRONI'IENTAND INIT IAL I ZATI{]N 147

Certi idge Ceitiidge Cartridte

Without Eooted Suppoft Pac&age tlith gooted EupPoit Pstk€9e

Dis kette-Booted

Sof tuare

Dis lette-Boot FiIe Fordat D i E k e t t e - B o o t P r ' o ce s 5 Saftpl6 Dis kette-Bootab le Prograln LiEting Progia$ to Create Di6kette-Boot FiIeE Caseette-Booted

gof ttare

C66satte-Boot File Foroat Cassette-8oot Proc esE S a o p1 e C . 6 s e t t e - E o o t e b l e P r o g t a L i E t i n g Prograo to Create CEssette_Boot Fi1e5

158 154 r$9 1s9 160 161 L64 165 165 ,.67

1 1 ADVANCEDTECHNIOUESAND APPLICATIAN NOTES Sound eenere t i on

170

Cepabiliti6r Conf I iE t6 l.lith OS

170 170

56?een Graphi,c5

171

Herduare Capabil ities O S C a p a bi l i t i e g C s r r o r C o nt r o I Colo. Contr.ol Alternat€ ChaFacter Setg

171 LVL L71 L7L t7?

Plager/i.1i€5 i le craphics

L74

H a r d | l r a i e C e p a bi l i t i € 9 Conf I icts lrith Og Rerdint

L74 t74

esfte ContFol ler'g

174

Kegboard Control ler SenEing Front Panel Connectorr is I/O Portr Hdrduate Infor'fiation: SoftuarB Infor.nat i on: Othea tliEcellanaouB Softuare

10

170

Infor.fiation:

t74 176 ,.7b 177 179

APPENDICES A p p e n di x A

CIA COMI'IANDBYIE VALUES

lAO

A p p e n di r I

CIO STATUS BYTE VALUES.

1e1

A pp . n d i x C

Stg

LA2

A pp l n d i r D

ATASCI I CODES

143

A p p e n d ir E

DISPLAY CODES ( ATASCIt )

144

A pp . n d i r F

KEYBOARDCI]DES (ATASCt I }

1€9

A p p e n di x c

PRINTER CODES (ATASCI I '

146

A p p e n di r H

SCREEN IiODE CI.IARACTER ISTICS

1Sg

A p p e n d1 r I

SERIAL BUS ID AND COI.ITIANDSUMMARY

191

A p p e n di r J

ROM VECTORS

19?

A pp e n d I x K

DEVICE CHARACTER I9T ICS

154

STATUS BYTE VALUES

Neqb odrd Di splag ATART 4lotTf.ll Progrem ReEoid er ATARI 82OtTM1 4O-Column Impaet P.inter ATAR! ElOtTMf Dist Drive Appendir

L --

Central

OS DATA BASE VARIABLE FUNCTIANAL DESCRIPT IONS

Data 8a9e D€sct iotion

ts4 194 194 195 197

200 200

FUNCTIONAL INDEX TO DATA BASE VARTABLED E S C R I P T I O N S2 0 1 A. !{EI'IORY CONFIEURATION

211

t1

B. TEXT/ORAPHTCSSCREEN CurEor. Contio 1 gEreen Mirg ing Tert Scrol I ing A t t r a c t M o de Tabbinq L o gi e a l T e r t L i n e s split Srreen DiFp larj ing Cont?ol Charact€rs E5cap€ (Displeg Follo{ring Control charactet'} DiEp lag Canttol Cheadct€rs l'lod€ Bit-Happed erEph ic5 I nterna I llorking VariebI.s Interna I Charscter Code ConverEion

2L2 213 e15 219 eL6 217

ela eeo ezl eel 2?t

C. DISKETTE HANDLER

e25

D.

223 Baud Rate Deteimination Ca6Eette ModE C a s s e t t e B r r ff e r Internal Worl in9 Vari.EbleE

227

KEYBAARD X e V R e E di n q a n d D e b o u n . i n g 9 p e Ei a l F u n c t i o n 5 Star. t/Stop Autol'ep€it Inverse Vi deo Control Console Kegs: tSELECTI,tSTARtl, PRINTER Printer-Bu++er' Interna I tlo, I ing vaii€bleE

229

eeo e30 231

and tOPllONl

232

E . C E N T R A LI / O R O U T I N E ( C I O , U s e r C e1 1 F € r € o e t e ? s 1/U

L O N E P O1

IJlOEX

Device Statu6 D e v i . e T a bl e CI O l H a n d 1 e r I n t e r + a c e P a t a n e t e r s Zeio-Page IOCB I nterne I l,lorking Veriables H. SERIAL I/A

R O U T I N E( S I O }

U6ea Call P€r'€oeters DeviEe Contro1 Eloc* Bu6 Sound Cont.ol Ser io I Brrs contr.ol Ratrg Logic C he c k s u n Data Buffering Generel BtJ+fer Control C o o o a o d F r a m e 0 u t p u t B t J+ f e r Re. e ive/Trenefii t Data Buffering S I 0 T i m e o ut l n t e r n e l W o rk i n g V a r i a b l e g

233 233 235 235

237

ee7

244 e40 241

ATART CONTRf]LLER5 J o r js t i c * E Paddlee Light Pen D.iving Control lerE

249 246

K,

DISK FILE HANAGER

247

L.

DISK UTILITY POINT€R

244

FLOATINO POINT PACKAOE

248

F o u e r - U p a n d $ g s t e f l R e 6 et

249

RAM 5i zin9 Di 6 k e t t e / C e s 6 e t t e - B o o t Environment Cdntrol

245

. N.

2eo 291

P.

F,

I NDEX

t4

INTERRUPTS Sgctem Ti nea6 Rerl Tifie Cloc I Sgrtem Timer 1 Sgst€|n Tim€r 2 SgEteor Timers 3, 4 and I R A t t l n t e r r u g t V e Et o r E NilI tnte.r.up t V6. tor5 I R O I n t e . r u p t V e ct o r E Haiduare R6giiter Updates Int€.na I tro.L ing VariabIes

e$3 253 233

USER AREAS

254

Alphabetical List of DEte Bese VeriableE ilFoo.g AddreEs Ordeird LiEt of Date 8€6€ Varieblee Float ing Point Pack€ge Variables

259

295 295 255 236 254

270 271

TAELE OF ILLUSTRATIONS Fi gure 1-1. Figure 1-2.

ATARI Home Conputer Bloct leleoorgLegout ChErt

Fi9u.e 4-1. Fi gur.e 4-e.

650A Sqst€n I'lapped t/O

Figur€ 5- 1. Fi gure 5-2. Figurd 5-3. Figure g-4. Figure 5-5. Figuie 9-6. Figure 5-7. Fiqure 5-8. Fi qur.e 5-9. Fi tur.e 5-1O. Fi gur€ 5-11. Utiliretion Fi gure 5-12. Fi 9u"e 5-13. lvleoorg Mep Figure 3- 14. of ContentE Figure g-15. Figure 3- 16. Figure 9- 17. Fi g'rre 5-18. Figure 5-19.

I/O SubsgEtenEtr!ctu.e Flou Diagram CIO Celling ilechaniBn A n l / O E x E o pl e KeVcode to ATASCII Conversion Table Text Hodeg 1 and 2 Dsta Form Or5!hiti Modes 3-11 eET D6ta Form C r ' € p h i c s l . l o d e E3 - 1 1 P U T D a t E F o r m Str.een Dicp latJ Elort Dieqiefi C a 3 s e t t e H € n dl e r R F . o r d F o . m a t Devi ce/Fi lanaoe SgntEx F i l e l . l E n E g € n e n tS u b € q s t e m D i 6 t e t t e Sector

llefiorg

Diegram

l'lep

MED

FiIe File

l v l a n a g e m e n t€ i u b s g s t 6 n S o o t R e c o r d F o . r . m a t l'lan:genent S!bsgstetn Boot PpoterE

File

M e n a g e n e n tg u b E g s t e r nV o l u E T a b l e

File I'lanagenent SubsUEtem9olufle 8it Mdp File Dir.ectorg Format File Manaqement Subsgsteo File Sectof FoiinEt Re5id€nt Device Handler Vectors D V S T A T4 - 8 g t e O p e r a t i o . r S t e t ! s F o l " n € t

2S

49 53 56 59 A4 74 B? 90 q2 93 93 94 95 96 100

15

Fi gure 6-1. List of SgBtem IntetruFt Eventg g u r e Fi 6-?. Interruo t RAll Vectof Initialiration Figure 6-3. P O I ( E YI n t e r r u p t M a 6 t E r a m p t e Figure 6-4. I n t e r r u p t a n d T i m e r V e c t o r R A MS t a c l Content Tabl e Figure Figure Fig!re Figure Figure Figure Fig ure Fi gure Figure Figure

lO- 1. 1O-2. 1O-3. 1O-4.

I / O S u b s g 6 t € mF l o u D i a g r E m D€vica table Forlll3t H 6 n d1 e . V e ct o r T a b l e Serial 8uE Coflnectot Pin Descriptions Seriel Bus ConnEnd Ftafle Format Ser i61 lls Timing Diagran

133 134 135 L46 144 151

Cartr i rlge Heeder'Foroat D i Ek e t t e S o o t F i l e F o r n e t DiEk€tte-Eoot€b le Prograft Li6ting S e l n p1 e C € E s e t t e * B o o t a b I e P r o g l . a f i

137 159 Ex.mpla

UEer-De+ined cherEcte. Set Eit lelenorgAddress lJser-Defined I r €} Charact€r' Hatrix git Table C h E r e ct e r B a E e D i a g r ' a n Re€ding Data Frofl an ATARI Keqbo€rd Contioller ATARI Ke!bo€r'd Control l ei Variable/Register v a l u e T a b1 e F i gu r e 1 1 - 6 . U 6 i n g F r o n t P a n e I C o n n e c t o r r A t l / Q P o r t s : P i n F u n c t i o n T a bI e s

Figuie Figure F i 9u i e Fig uie Figuie

16

11-1. 11-2. 11-3. 11-4. 11-5.

t02 108 1to

173 L73 176 179

PREFACE This rl€r|oal deEcribes the r.sident Operating ggste|'l (US) +or the ATARIe Hofie Computea. tor readers oho are f€miliar urith the int€rnel behavior o+ f,he E96tem. It diBcusEes: Sgstem funetion6 and utilization

techniqueE

S u b 6 q 6 t e mr e l a t i o n 3 h i p s € n d o r . g a n i r a t i o n Cher€ct€risticE of the ATARI peripheral devir€6 that can b € € t t a c h e d t o t h e A T A R I 4 O O I T H ] a n d A T A R I A O O IT t r u H o m e Co ! uter A a l v a n c e dt e E h n i q u e s f o r carEbiliti.eg

going beqond the baEic Og

The goneral featur.es of bg the OS.

t h e E o f t p r . r t e r .s g s t e o h a r ' d l r a r e u s e d

It uould be helpful to have a f€oiliaritg { r i t h p r o g r . a m m i n gc o n c e p t E and terninolog!, assenblg language proqramfling in gene.ral, th€ Sgnertek 65Oe in particular, and digital herduare concepts arld ter.ninologgrrou uill be provided !rith the infornation gou n€ed to uBe the OS reEouices, trithout r.egorting to trial-and-er?or t€chniques or the Og !isting. Supporting information *or taskE that involv€ OS I iEting references i9 also pr'ovided. T h i s l n € n u € 1d o e E n o t p r e s e n t a c o { n p r e h e n s i v €d e E c r i p t i o n o + t h e hardqrEre used to prov:d€ OS iapabilites. T h e p i o g r ' a m m e t .u h o n e e d 5 t o go begond the rapabilities descr.ibed Ehould consult the ATARI Home C o m p u t € r H e r ' d { r a re H € n u €} .

O P E R A I I N GS Y S T E } 4C 4 1 6 9 5 5 - -

Section

1 I7

1

INTRODUCTION

CENERALDESCRIPTTONOF THE ATARI HOMECOIIPUTERSYSTEI'I i n t h e A T A R I @4 O O t T M l a n d A T A R I E O O I T M ] H o m e Bper€ti.ng iqstenr The primarg differenceE bet{reen the turo are: Computer are identicel. o

Phgsicel Faclaging

o

The ATARI 4OOComputer con6ole h€5 one cartridge slot, rlots ATARTBOOComtutei console hes turo certridge

o

The ATARI 4OO HomeCornputer contain6 l&l{ RAMand cannot be expanded. The ATARI 8OO Home Conputer can be erpanded to ts mer iflun o+ 4AK RAt'l.

o

Th€ ATARI 8OO conpstei' Comouter does not.

has a nonitor

Jack,

the

th€ ATARI 4oo

The Heiduare Circsitrq o p?oduce6 both Eheracter and point uhite (B/tll or color television.

g.aphics +or blac& and

o Produces four independent €udio channels (trequenE" cont?o1led) u,hi€h use the televi€ion Eound sUsten. o Provides one bi-level

audio output

in

o InterfaeeE uith ContTolters.

up to +our Joqsticks

o Interfaces

a ser'iel

uith

o Contains E built-in

I/O bus for

the baEe unit. and eight

Paddle

sxpanEion.

k€qboerd

Figure 1-1 preEents a simpIi+i€d block diagiam of the haiduare. See ths htsrdureren€nu.l for Eupgor'tinq docu|nentation.

O P E R A T I N GS Y S T E HC O 1 6 $ 5 5 - -

1B

Section

1

r 6502 | i p l ' o a e 6 s o ri +----+----+ +---------+

ROM

+---------+

+---------+

IDgOO-FFFF I

RATI

I OOOO-r x x r t---------+E I Pforessor externEl bus

i I

+---------+ 1......... ; IRO I

iCartridge I I o t s A&BI IBOOO-BFFFI +-----*---+ I PIA

+---------+ I cont?ol- i I er oorts !

Jogst:€ks +--------+----------+ i -------+

+--------

I

i

ID 3 O O - D 3 1 F + - - - - - - - -i - - - - - + +---------+ I i : |

| t |

+---------+

| i

| I

ilegboard i idata legsi

+---------+

+--------i-----t-i--+ + BREAK I i . . . . . . . . . I D2OO-D21F+-------i ---+ | | +---------+ I +----+----+ IRO audio | ! ! I on/off +------------i +---------+ i -+ | | i +----+----+ i + + cassette trig5 I i i i I i +--------+ I CTIA i i i linterfacei +-----+ i +-l-i----+ I ! DOOO-DOlF+----- i -- | -+ i ! +---------+ +----+----+ i I i i +----+ eerial I i video I I i I i t/o I DMA +----+----+ litpen i i +------+ bug I .....-...1 ANTIC +--------+ i 1.........

iD400-D41Fi

|

|

'

i

NMI

conpo6it€ audio/video

t"----+

froo I console CTIA -+ speeker

i i

+---------+

i i

+---------+ i START, I OPTION

Figu'.e 1-1.

A T A R I H o f l r €C o n p u t e r B I o E t D i a g r € f t

OPERATINGSYSTEII CO16555 --

Se.tion

I 19

CONVENTIONSUSED IN THIS MANUAL T h i E m t s n u e lu 6 e s t h € f o l l o u r i n g s p € a i € l

notetions:

H €r a d e c i | n € l N u m b e r s A t l t u i o - d i 9 i t n u { n b e " sp r e c e d € d b q a d o 1 1 € r s i g n ( $ t d e s i g n a t e hexadecimal nuobers. All other nunbers (exE€pt ftemorg addresE€E) are in deci.nal +orm snless other{ri6e EpeEified in the suppor.ting t€tt. Me$or.gAddreEEes A11 ie+erenEes to co puter nenorg ard mapped I/O IoE:tion5 a?e in hex€decimal notetion. Meoror! addres5€6 fieg oi lnag not be contEined in Equeie brac&etE. (ExaflpIe: CD2OFI snd OzOF eie the sarne Bddf esE. )

Ki lobg tes

of l,le|norq

I t l e m o r gE i z e s a r e f r e q u e n t l g as 32K, urhere a tilob{te is

erpressed in unitE of kilobqt€i, 1024 bgtes of oemorg.

P A S C A LA s a n A l g o | . i t h o - S p e c i f i c a t i o n

such

Language

T h e P A S C A LI e n g u € g e ( p r o c e d u ? E b l o c l o n l g ) i s u s e d a 9 t h e specification l a n g u a g e i n t h e + e u p l a r e s | , h e r . €E n a l g o r i t h t n i E ipecifi€d i n d € t a i 1 . P A S C A Ls g n t a r i s 6 i n i l € r to ang numbei o+ other bloct-strlctuied lEnguag€i, end gou Ehould have no dif+icultg follouin9 the eoda presented. MeoorrJ Lag out s Diagrems similer to Figure 1-2 el.e used uhenever.pictures ot teble6 .re oaesented: 7 6 3 4 3 2 1 0 +-+-+-+-+-+-+-+-+ i i --+-+-+-+-+-+-+-+-+ + ---

This

i6 e single

of bqtes

bqt€.

This is a uJord (2 bgte5).

+-+-+-+-+-+-+-+-+ i

i

--r +-+-+-+-+-+-+-+-+ Figure

1-2.

i

This iE a blorft o+ |tlenorq of unspecified length.

Menorg Lagot',t Chsit

OPERATINGSYSTE|4CO16S53 --

Section

,.

A i t 7 i E t h s m o e t E i g n i t i c a n t b i t ( H E } B )o f t h e b { t e , iE the least Bignificant bit (LSB). '

In t€61es snd figure6, botton of the figure.

and Bit

dtemorgaddreEses a1{r€qs increa6e

O

touard

the

Baclu6-Naur Forft A nodifi€d version ol Baclur-Naur Forn (gNFt iE uscd to Exg?es9 sone sgntaEtir forras, rrhere the +ollouing o€talinguistic 6Vmbotsera used: : := <

is )

i t

the sub6titution

a netesgntactic

(aiiignnent)

operatoi.

vErieble.

sEp€?etes al ternat ive subEtitutiong. I

an optional

conEt?uat.

Angthing elEe is e slntacti€ it6€lf.

literel

conrt€nt,

{rhiEh Etands for

F o r E x a n p1 e : <device Epe€ification>

: : = {deviEe nafle)t<devi.e nurnbei}l:

< d e v i c e n a . n e >: : = C i D ! E i K l P i R t S <deviEe nuftbei>::=

I l2 i3l4l 5l6 !7l A

A ridevice specifi.ation,, con6ists of a lnEndatorg ,,devic€ name,,, fotloured bg en optional "device number,,' folloued bg the mandatorg colon charecter. The device neme in turn llluit be one of the char€cters shoun as alternativeE. The devi€e n!flber ( if it iE Diesent) muet be a digit 1 through A. OS Equate Fi leneneE U p e . a t i n g S g s t e m R O M ( R e e d O n l U l ' l e o o r { } a n d R A l " l { R s n d o { t lA € E e s s l ' l e m o r g l v e € t o i n a m e s , R A l " !d e t a b e s e v a r i a b l e n e m e s a n d h € i d u a r e regi.ster n€nes are ell referred to bq the names€Esigned in the Og p r o g ? a m e q u a t e 1 i 6 t . l ^ r h e no n e o f t h e g e n e i n e s i s u s e d , t h € m e m o r g e d d r e s E i E ! s u a l . l r J p r o v i d e d , s u c h a e E O U T A Dt 0 2 4 2 l .

A P E R A T I N CS Y S T E MC O l 6 5 5 5 - -

gection

1.

2

OPERATINO SYSTEI{ FUNCTIANAL OROANIZATION

This seation descri.beE the various genera I teitng.

subs{rsteos of th€ regident

OS in

Inputl0utp ut Subigiten The Input/Output (I/O) subsgstem provideE a high-IeveI inter'+a.e betueen the paograor and thE harduar€. Ho6t functions are device-independent, su€h a9 the ?eading end uriting of chaiacter dett, p r o v i s i o n E d e v i c e d € p e n d e n t f ! nctions as {rell. h € v e b e e n f o r o a d e vet All periphrral d€viceE capEble of dealing uith .haractei data hsve i n d i v i d u € 1 E q l | l b o l i c n a { n e E( E [ r c h a E K , D , P , e t c r . € n d c a n b e a c c e E s e d using a Csntral I/U (CIO) routineA R A t ' ld a t a b € i e p r o v i d e s e c c € 6 s t o c o n t r o l l e l ' s ( J o ! s t i . k E a n d p a d d l e controller6), i l h i E h d o n o t d e € 1 u i t h c h a i a c t e r d e t E . T h i 5 R A t ' ld a t a base is periodicallg updated to sho{, the states of these device9. INTERRUPT PROCESSINE The inter.upt s r J g t e mh a n d l e s € 1 1 h a r d u r a i e i n t e r r ' ! p t 9 i n a c o m m o n and €onsistent manner'. BrJdefault, al I interiupts aie fielded bg inte.ruptE (oi the OS. At gour discretion, individual pioqrem. gaoupE of interrupts' can be fi€lded bq the appli{ation INITIALIZAIION po{ter up and The rUstem provides tto Ievels of initieliz€tion: s{stem reEet. The OS per'formg pouei-!p initial i zation eech tirne the E!stem pouer iE snitched to ON, and sqstem r.eset i . s p e ? f o r m e d e a c h t i m e t h e t S Y S T E I 'RI .E 9 E T I f t e q i 5 initi€lization pressed. Pou€r-Ut The OS eranine6 and notes the configuretion of the unit the gqsten po0rer is suitched to ON. The sqEtem perforos tasls at pouer up:

O P E F A T I N OS Y S T E MC O 1 6 5 5 5 - -

SeEtion

2

uhenev€r the follouing

o

D e t € r n i n € E t h e h i g h e E t R A Ma d d . e 5 5 .

o

Claari

o

Establishes all

o

Foi|nats the device

o

InitialireE

o

Set€ up the 6cr6en +or e4 r 40 text

o

Boot6 the cesE€tt€ if

o

ChectE cai'tridge Elot(E)

o

Boot6 the dickettr iB ettech€d.

o

TainEfdr's control to the €aitridge, dislette-booted caFsette-booted prog!'a|n, or blac&boafd pno!lram.

aII

o t R A I ' It o

zeros. vertors.

RAH inteirupt tabl€.

the cartridq€(5).

if

mode.

directedfor

diElette-boot

diracted

instructions.

to do Eo and € disl

drive

unit

progralnl

TSYSTEH.RESET] P i e s s i n g t h e I S Y S T E | .R |.ESET] teq ceuses the Og to perfo.|n these fo l l oqring ta5t3: the Og por.tion of RAl,l.

o

Cleari

o

RecheE*s tor

o

Reestab liih€5

o

Foiftats

o

Initializer

o

Eats up the Ecr.een for

o

TranEfeF: control to the car.tridge. a diskette-booted pr.ogr€n, a casgette-booted prograo, or the blaa&b06rd program.

of RAM. ell

the device

RAl.lintel.ruot

veEto?8.

table.

the cartridge(s). 24 x 40 tsxt

N o t e t h E t I S Y S T E F IR. E S E T ! d o e 6 n o t p e i f o i n tas*s listed in the pouer-up section.

node.

all

OPEFATINGSYSTEI'ICO16955 --

the pouer-up

Section

e

23

FLOATINE PAINT ARITHMETTCPACKAOE T h e O S R O Hc o n t a i n 3 € F l o a t i n g P o i n t ( F F ) p a q k a g e t h a t i 6 € v a i l a b l e to nonrEsident piograne such as ATARI EASIC. The pactage i6 not uied bU the oth.|' pattE of the OS itiel+. The f l o a t i n g p o i n t n u l t l b e r sa r e i t o r e d a E 1 0 g C D d i g i t F o f o € n t i s E a , p l u s a l-bgte exponent. The pactage aontains theEe routineE: o

AgCII-to-FP

o

tnteger-to-FF

o

FP add, 5ubtr€Et,

o

FP 1og, €xp, end polgnomiEl €valuation.

o

FP nunber Elear,

and FP-Io-ASCII

conversion_

and Fp-to-integer oultiplg

load,

convFr€ion.

and divi.de.

store,

and nove.

OPERATINo SYSTEI'ICO1655S --

Section

2

3

CDNFICURATIONS

T h e A T A R I 4 O O a n d A T A R I 8 O O H o r n €C o t n p u t e r s s u p p o r t a t id{ val.ietg of configlreti.onE, eech urith € uni.{ue operating envir onment: Ca.tridge(E)

ma! or

€g not

be in9erted

a d d e d to F l e m o F gr a n b e o p t i o n a l l g Eonso 1e in 16K increm€nts p€iipheral Hen{ different EariaI I/0 buE.

the ATARI goo codtputer

devi ce6 can be attached

to the

The OS accounts for all of th€6e veriBElei urithout .equiiing E (iee 9eation a). The $€chine change in the resident OS itself e o n f i . g u r a t i o n i s r h e c k e d { r r h e np o u e r i B f i r s t torned on and then A general i 5 n o t c h e c l e d E g a i n , u n l e 6 E e t J s t e mr € g e t i s u t e d . discus6ion of Eomeo+ the velid ronfigu?ationE follous. PROORAMENVIRONITIENTS Tha OS ElIo{rE on€ of four progra(n tqFes to be in contrdl ooint in time:

at ang

The Og b1ts€lboBrd (ATARI Meno Ped) ptogratn progrem

o

A c€r'tridge-reEident

o

A diskette-booted

o

A cassette-booted pl'ogram

piogi€m

Conttol choice is baged upon in+oroation in the caattidge(5), upon urhether or not a diEk drive is Ettached, snd upon operstot kegboard input€. Th€ exact €lgorithms ere di5cu55ed in detail in 9ection 7. Bl€clbodrd ModE In blactbosrd oode, th€ screen is €stablished aE a 24 x 40 text screen, Angthing entered from the kelboard goas to the screen rrithout being etalrlined, €lthough eI1 of the screen editj.ng functionE ai'e .upported. Elacftboaid moile is the loorest prio!'itU e n v i r o n m e n t . Y o u g o t h e . e o n l q b g c o m m a n d+ r o | n e h i 9 h e r OPERATINGSYSTET'ICO16555 --

Section

3

prioritg environnent, or bq defa!:t, if there iE no other rea6on€bIe envi?onoent for the OS to enter. For er€ftp1e. t{ping BYE in BASIC cauEeE the OS to enter the bleEkbos.d mode. The b1€c|(boeid n o d e . a n b e e r i t e d b ! p r e s s i n g t h e t g Y S T E t ' lR . ESETI keq i+ it uas ente"ed froo a higher envlronment. Ca.tridge An inserted Eartridge normallg provides the tnein Eoot?oI e+ter initieliration iE conpletE (for erample: ATARI BAEIC, SUPER SREAKOUTITIT{1,EASKETBALL, COI''PUTERCHESS, and otheF6. All these caitridqe programs intelfac€ directlg uith rrou in sone uaq). Although a cartridge ran paovide a suppoiting function for 6ooe other Frogr.ao €nviron|nent, this has not qet been done. Some€a?tridgeE (perticularl{ fteqboard-orisntad oneE) can Ehenge environoent5 bq entering spe.iel a o m m a n d s( i u a h a 9 " B Y E " ) t o 9 o t o b l a c k b o a a d m o d € o r " D O S " t o e r t e r the disl utilitS. Other ce?tridges csnnot chEnge envi.onnentE. Note p?eventE the remov€1 or inse|.tion o+ a that a haadu€.e interloc|( cartridge {rith the pouer on; thiE fe€ture rsuser the entire sqstem to reinitialire !rith ever.q cartridge change. Dl skett6

Eoot

The diil€tte marl or oag not be booted {rhen the 6g9ten pouers up qrith di6lette-bootable ioftuare. T h i s p a r a g r . a F ha s s u | l l e st h e t a di6Lette boot did o€cur. See Section 7 for boot condition erplanations. The diEtette-booted Eofttare can take €ontrol EE the Dist Utilitg P"ogr'am(DUPI doeg under certain conditions, or ran provide a s u p p o r t i n g { u n r t i o n a s t h e F i I € M e n a g e ( n e nS t gEtefl (FMS} does. Thi.g envitontrlent iE so +Ierible that it is difficult to generalize on itg cepabilitie6 The onlg fiachine Fequireo€nt (other and a€Etrictions. t h a n t h e d i E t d r i v e ) i E t h e t 6 ! + f i c i e 1 1 t R A Mb e i n s t E l I E d t o s ! p p o r t th€ p.ogran baing booted. Cassette-Boot The cassette-boot enviionnent is sinile. to the dis*ette-boot snvironment, elthough the caE5ette is limited as an I/tl device. It is slou End can ecceEs onlq one file €t,a time in Eequence- Note that the f,a6Eette-boot fa€ilitq ha9 no relation to the sse of c 6 6 s e t t e s t o s t o r e h i g h - 1 e v e l l a n g u a g e p r o g r . ] r n g( e . 9 . , p r o g i a 0 n E uritten in ATARI BASIC), nor to the use of r€s6ettes to gtoie det€.

OPERATINGSYSTET'ICO16595 --

Sertion

3

RAII EXPANSIAN Altho!qh golJ can erpend RAHnonrontiguouElg in the ATARI AOOHooe Cooputer, the OS orill onlg recognizs RAI'I that is aontigrrols Etarting froo loEation O. InsteLletion diiettions a r e p r . o v i d e d u i t h t h e p u r a h s s e d R A Ml l l o d u l e s . R A M c a n b e edded until it totsIE 4gK. After 3eK, additionat RAH ove.lagE f i.rst th€ right-certridqe addres6es (32K to 4Ok) and then the left-c€l.tritlge edd!.eeEe6 (4OK to 48K). Note thet in cases of .onfliat, the inEerted cartridge has higher prioritg and diEables the confli€ting RAMin EK incaenentg. gee SeEtion 4 for a detailed discursion of Eqstemo€ftorg AE € result of polrei-up, the OS lrill qener3te t0ro FointerE that d e f i n e t h e 1 o ! r e 6 t a v a i l e b l e R A l . ll o c a t i o n a n d t h e h i g h e s t a v a i l a b l e R A F Il o c E t i o n . T h e U S a n d d i 5 k e t t e o l . c a s s e t t e - b o o t e d i o f t u a r e u r i t l dete?oine the locetion of the loueEt aveilable RAt{, uhi.le the nl.|lber of RAfl noduleE snd the current screen node uill deter.(nine the highest available RAM. PERIPHERAL DEVICES Feripherel devices of several tgpes csn be sdded to the sVstem using EtandBrd cables to either. the 9erie1 bus or' the connectors at t h e f r o n t o + t h e € o n p u t e r E o n s o l e . T h e $ o r t c o m r n o nt g p e 6 d e a l r r i t h €ith€r tranEoission of bUte6 of data (u5ua11g serial bus' or tiEnEfiisEion of sense in+ortnetion (u5u:l1u oan€ Eontrollers).

GameControIlerE The OS pefiodic€1Ig senges (90 or 60 timeE pel Eecond) the Etefldeid (P€ddle9 and Jogsti€k5) end the vaIue6 read €re gaoe rontroller6 Btored in RAl.l. You ran pIug in, remove, and reerr'ange thege controlleis E t r ! i l 1 { r i t h o u t d + f e c t i n g 5 g s t e m o p e i e t i o n , b e c a { J s et h e sgstem uill elua{rs trq to reed all of there rontrotlerE_ The Driving Controllers €r€ l.ead, but not de.oded, b'J the OS. sp€ci€I (Eee inEtiuction5 are requi.ed to read the tegboard controller S e c t i o n 1 1l . Piogaafi Rer ord ei T h e A T A F I 4 l O t T M l P r o g r a r nR € . o r . d e r i 6 a 5 p € c i E t p e r i p h e f a l . It uses the seriEl bus to send end r'eceive data, but doee not confo"n to the proto€o1 o+ the other peripherals th€t uee th€ serial bus. The Prograo Re[oider must also be the last d€vi€e on the Eerial buE, b e t E { , t g ei t d o r s n o t h a v e s s e t i e l b u s e x t e n d e f c o n n e c t o r e E t h e other peripheF:lg do. Ihere Eal| never be moae than one pr.ogreln Recoider connected to €ng sggteo +oi the sam€ re6son. The sqsten .annot €€nge the pre6ence ot abgence of the Progra& Recoider, Eo it €en be connected and diEconflected at ui11. O P E R A T I N eS Y S T E I IC O l 6 5 9 9 - -

Section

3

SeriaI

BUEDevires

A Eeri€l bus dEvire conforrns to th€ seiial I/O bqs trotoEol aq defined in Section 9, but thiE does not incl!de the prograrn Recoi.der. Each seiial b!6 device hEs tuo identical connsEtor5: a Eerial bus input, and a rerial b{rr ertender. Eithei connector can b e - u s e d f o r e i t h e r ' p u r . F o i e . P e r i p h e . a l s c e n b e . , d a i 9 q E h a i n e d , ,b q €abling them together in a cequenti€l feEhion. Ther€ are usuallrg no t.sstrictions on the cdbling oide. because esEh d€viEe has a unique identifier. lilhere re5tr.ictionE erirt, theU o,itt be mentioned in S e ct i o n 5 .

2S

0PERATINo SVSTEfi CO16555 --

S€ction

4

4

SYSTET'IIIEHORYUTtL I ZATtAN

H e m o l ' gi n t h e 6 9 s t e m i s d e c o d e d i n t h e f u l I 6 4 K r a n E e o + t h e 6 S O a mrcr.ocodrputea end there €re no piovisions for 6dditionel fiapping to extend dreoorV. Memorg i.. divided into four be9i.a regi.ons (uith 5one over'1ap poi6ible): RAH, cErtridge area. I/O regiot| and the resident Og ROH. The regions and theii address bo!nd€rie6 ere listed belou ( a 1 1 a d d r e s E e sa r e i n h € r a d e c i m e l ) : 0000- lFFF

eooo-7FFF BOOO-9FFF AOOO-AFFF

coo0-cFFF DOOO-D7FF DSOO_DFFF

Figlre

4-1

RAM(minimufl rsquired *or o0er.ation) RAM e rpans i on area C6rtridge B? Cartridge A (hs1f of 16K size) Cartridge A or RAl.l UnuEed Harduaie I/B de.ode6 Fl oat in9 Point P€rkEge (US) R e si d e n t O p e r a t i n g S g s t e n R O t ' {

or RAll

6502 Sgstem Menoru l'lep

This secti.on {tri11break the5e regions into even 6maller function€I diviEione and pr.ovide deteiled explanEtionE of their u5age. RAH REEION T h F O S a n d t h e c o n t r o l p r d g r e n 6 h a r e t h e R A Mr e g i o n . T h e R A H r . e g i o n can be fuither EUbdivided into the follouing sub negions for d i E c u 6 5i o n p u r D o E e s : Paqe O = 6502 page zero Eddiess mode region. Page 1= 6502 st:c|( region. Pege6 2-4 = OS d:teb:se €nd uEer {rorlipace. PageE 5-6 = U6e!. progran uror*6pace. P e g e a 7 - X X = B o o t a b l e s o S t u , a i e a r e a / f r e e R A l , ln. P a q e E X X - t o p o + R A M= S E r e e n d i 6 p l a q l i s t a n d d a t a . * Note that amdunt of

XX ie e function RAl"i in6tal Ied.

of

the

screen

gr€phics

ttloda€nd the

T h e p a r a g r s p h s t h a t f o l l o t , d e 6 . r i b e h o u t h e O S u s e s R A ME u b r e g i o n 5 , e n d p 1 " e s e n t 6u 6 e r p r o g r a r n r e c o m e n d e t i o n E . O P E R A T I N CS Y S T E i 4C O l 6 5 9 5 - -

Sertion

4 29

Page o The €rchitecture of the 6302 microconputer instruction 6et and addr.essing nodei givEE psge O speci€1 EignificanEe. ReferenreE e d d . € s s e 9 i n t h a t p a g e ( O O O Ot o O O F F ) e r € f a s ; e r , reqoiis {euer instruction bgtes, and provide the onlg oech€nism +o. ha?duere indirect €ddr€sEin9. Page O should be used 6paringlg so that al porEible use.5 can have 6 portion o+ it. The OS pern:nentlq tal l o u € r h e l + o f p a g e O ( O O O Ot o O O T F ) . T h i s p o r t i o n c a n n e v e r o e ang outer.nvironment unless the OS is comptetelg disabled and inteirupts to the 8S aie elininsted.

to I e6 the used bg A I I

T h e u p p e r h a l + o f p a g e O ( O O B Ot o O O F F ) i E e v a i t a b l e t o o l t e r environoents trith the follouing restriEtion: the ftoating point pEElage, if ured, fequires OOD4through OOFF. Page 1 Page 1 i3 the 55OZ h€.duare €tack region; JSR inEtruEtions, PHA inEtauctions, snd inter.uptE all cauEe data b{tes to be l,ritten to pege 1. ConverE€lU RTS, pLA, €nd RTI instructions aII €ause data bgtes t o b e r e a d f r . o o p e g e 1 . T h e e S 6 b g t e 6 t a c k i 6 e d e q u e t € + o r n o r m at s u b i o u t i n e c a l l s p l u s i n t e r . r . ! p t p r o r e s s n e s t i r g , s o n o r . e s t r i . c t i on6 have been l|ladeon p€ge 1 uEege. It is obviouE that a stact of th i 9 size is totellq inedequate for dEepIg reEUisive proce66e9 or +or ne5ted proceE6es uith large loc€1 environm€nts to be saved. So, Eophistic€ted applir€tions. Eoft0rare rnainteined EteEfts nuEt be i m p I E m e nt e d . The 6502 6tact pointer iE initialired at pouer-up or 6q6tem reset to point to Iocation O1FF. The 6tack then pusheE dounusrd touard O1OO. The stict uill u r a D e r o u n d f r o m O 1 O Ot o O 1 F F i f a s t s r k o v e r f t o u condition occu?s, because o+ the nature of the 6502'E 8-bit stact pointer r€9iiter. OS Data Eeie L o c € t i o n g O 2 O Ot h r . o u g h O 4 7 F a r e e l l o c a t e d b r t t h e O S + o r u o i k i n q vtsri€bles, tableE €nd deta buffers. Poitions of this region can be used onlg after gou deterftine thet nonconflict rrrith the US i5 guer.snteed. For' exeopla, the printer and da6sette bLrffers could be used if L/O opet'€tionE to the5e deviceg are impo€sible urithin the controlling environment. The amount of uor|( involved in deter.mining nonconflict seemg to be coopletelg out o+ line 0rith the bene+its to be gained (erc€pt for a fe{r trivial c a s e s } a n d i t i 9 r e c o m n e n d e dt h a t pages 2 through 4 not be uged ercept brJ the US.

O P E R A T I N GS Y S T E I ' C I O16555 --

30

Section

4

User Nortspace LocatiqnE O48O thaough O6FF €re dediceted *or outer environment u6€ ercept {rhen the floating point paEkage is uBed. The +loating point package ureE loestions O57E through O9FF. B o o t R e gi o n Prge 7 is the Etirt of the "boot rEgion. " Whenso+tuere iE booted fron eithef the diskett€ or the caesette, it c€n st€rt et the louest free o $ t n o t l a d d r . e a c ( t h r t i 6 O T O O )a n d p r o c e e d ! p u a r d ( a l t h o u g h i t c € n a l s o 5t6tt at.ng a d d t e E s a b o v e O T O Oa n d b e l o t r t h e E r ! . e ! n d i E p l a r J l i E t ) . T h e t o p o f t h i s i a E i o n d € f i f l € 6 t h e 6 t a r t o f t h e , , f r e e ( n € { n o r r j ' ,r e g i o n . [,lhen the boot pr.oEess is EotnpIete, a pointe" in the d€t€ baEe containg the 3ddt'esEof the nert €vailable location above the goftdare JUst booted. Whenno softuare ha9 been booted, thi6 rointer contains the velue OTOOScreen DiBpleg LiEt and Dat6 Wh.n th€ OS is hendling th€ screen displarJ, the di.pl€q liEt that de+ines the srreen ch€raateristiEs End the .urrent d6ta that i6 contained on the Fcreln are rlec€d 6t the high address lnd of RAM. The b o t t o . n o + t h i s r € 9 i o n d € f i n e s t h e end of the free oemorq region and its 1oc€tion i6 a +unction o+ thr scieen ftode cuirentlg in ef+ect. A pointai i.n the data base aontaing the addresE of the I€Et availabl€ loration belou the screen reoion. Free l,leftorg Reg i oo The +r'ee nenorg t€gion is all the RAt{betd€€n the end o* the boot region End the rtart of tha screen region. Tfte outer Ievel applir:tion iE r€sponEible foa managing the free ftefioag regi.on. CARTRIDEESA AND 8 There are tuo 8K regiong regarved for. plug-in EErtridge6. Cartridge E, that i€ th. right-hand ceFtr.idge stot +ound onlg in the ATARI AOO Home Cotnputer, ha€ been allocated me orq addrosres 8OOO through 9FFF. CErtridgs A (the 16ft-hend cantiidqe slot in the ATARI BOOCo$puter. ronsole, €nd ths onlg rlot in the ATARf 4OO Cof|lgutei. . o n E o I e ) h € 3 b e e n a l t o c a t a d m e n o r g a d d r e E s e s A O O Ot h f o u g h 8 F F F a n d optionallq S O O Ot h r . o u g h B F F F , f o r I 6 K c a r t r i d g e s . I f E R A t ' tf i o d u l e i s p].uggedinto the lagt slot guch as to overls{ ang of thes€ addr€sseE, t h e R A l , lt € k e E p r e c e d € n e e e s l o n g a s t s c € r t t . i d g e j s n o t i n s e ? t e d . Ho{rever, if e dar-ti.idge is inserted, it uill disable the entire E o n f l i E t i n q R A I ' Il t l o d u l e i n t h e l a s t s l o t i n B K i n c r e m e n r E .

OPERATINe SYSTEH CO1695S --

Serti.on

4

MAPPED I/O The 4502 perforos input/output op€r€tions bg €dd.eEsing the €rtern€l support chip6 aB memorg, sofle chip retiEterE €re reEd/urite lrhile (the ATARI Home Computer others ere read_on1g or rrriie-onlg HarduEre l'lanual gives descriptions of 611 of th€ external registerE'. t l h i l e t h e e n t i r e € d d r e s 6 6 p a c e { r o r n D O O ot o D T F F h a E b € e n a } l o c a t e d foi L/O decoding, onlg the follouing subfegions arE used: DOOo-DO1F = D2OO-D21F = D3OO-D31F = D4OO-D41F = Figure 4-?.

CTI A POKEY FIA ANTIC

tlepped I/u

RESIDENT 05 AND FLOATING PAINT PACKAOEROT,I The region from llgoo through FFFF:lue{s containi the OS and the floating point pa€kage. Cere 6hou1d be t:*en to avoid u9in9 ang entig pointE that ar.e not guarenteed not to move, to €lIorJ for the possibilitg that another, but function€11q competible, OS can bc gen€rated in th€ future. ThE BS conteins mang vectored entrU points et t h e e n d o f t h e R O Ms n d i n R A H t h a t u i l l point not move. The floating paeldge is not vectored, but a1I documentedentrg pointB qrill be f i r e d : D o n o t u s e u n d o c u m e n t e dr o ! t i n e E + o u n d b g s c a n n i n g t h € l i E t i n g . A 1 i s t o + t h e f i r e d R O Mv e c t o r s c a n b e + o u n d i n A p p e n d i r J . CENTRAL DATA BASE DESCRI PTI DN See Appendir L.

MEI'IDRYDYNAT.IICS T h e f i e e m e m o r qr e g i o n i E t h a e a e a b e t u e e n t h e e n d o f t h e b o o t r e g i o n end the Etart of the screen r.€9ion. Aa ruch, its timit6 are variable. M E M L At O Z E T l d e f i n e 5 t h e b o t t o | n o + t h e f r e e r . e g i o n , a n d t ' l E H T O pt O A E S I defineE the top of ths r.egion. This section pr€Eents the conditionB that ce!6€ tfie setup or €1te!.stion of theEe variables

O P E R A T I N eS Y S T E MC O 1 6 5 5 5 - -

Section

4

Sgsteln InitiEliuation

pr.ocess

The OS deter'nine€ the ertent oa the Iouest blocL of contiguolrg RAl,l, and saver the limits. lhe Screen Editor iE then opened, thus setting a n e { , ( a n d I o l r a r } v t s I u e i n H E H T O P .D i g k e t t e o r E e E s e t t e - b o o t e d s o f t u e r e mi9ht be brought into fieoortr, th€t {rould pr.obebtg set a ne!, (and h i q h e r ) v a l u e i n M E I ' | L O( s e e S e c t i o n 7 ' . t t E H L Oa n a U g n t O p u , i l l d e f i n e t h e m a x i u f i a n o u n t o f f r € e n e { n o r . qa v e i l a b l e uhen the appliEetion progi€n finallg Thdt Emouht of fr.ee rnenor! cdn lete. 9et6 rontiol. d e c , | ' e e s e ,€ s d e s c r i b e d i n t h e n e x t p a r a g r a p h .

C h e n gi n g S c r . e e n l ' l o de 6 The Di6plag HEndlei interpr.tE t h e v a r . i a b l e A p p l t H I . t O O O E l, t o c 6 n t a i n *he addreis b€1ou lrhiEh i.IEMTOP cEnnot €xtend. ThiE allotrs rJou to pt'otect the poition of *r.ee menorg slace thet rJou aie uEing from being overuritten €s a feEult of screen node Ehange. The displag h3ndler l,ill 5 e t t h e s . r e e n + o r n o d e O , u p d a t e M E H T O P ,a n d i e t u . n a n e r r o r 9tatus to 9ou. i+ it deterrnineE thEt the screen oefioig uill ettend belou, APP|{HI as E re6!lt of e scre€n node ahanqe. In other cases the DlEplag Handler effects the desired oode chsnge and !pdEteg t,IEMTOP.

OPERATINGSYSTEf'|CO15555 --

Section

4