Amstrad DDI-1 manual Disc Organisation, Common to ALL Formats

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5.5 Disc Organisation

The BIOS supports three different disc formats: SYSTEM format, DATA ONLY format and IBM format. Under AMSDOS the format of a disc is automatically detected each time a disc with no open files is accessed. To permit this automatic detection each format has unique sector numbers.

3 inch discs are double sided, but only one side may be accessed at a time depending on which way round the user inserts the disc. There may be different formats on the two sides.

COMMON TO ALL FORMATS

Single sided (the two sides of a 3 inch disc are treated separately).

512 byte physical sector size.

40 tracks numbered 0 to 39.

1024 byte CP/M block size.

64 directory entries.

SYSTEM FORMAT

9 sectors per track numbered #41 to #49.

2 reserved tracks.

The system format is the main format supported, since CP/M can only be loaded (cold and warm boot) from a system format disc. The reserved tracks are used as follows:

Track 0 sector #41: boot sector.

Track 0 sector #42: configuration sector. Track 0 sectors #43.. #47 unused.

Track 0 sectors #48.. #49 and track 1 sectors #41.. #49: CCP and BDOS.

Note: 'VENDOR' format is a special version of system format which does not contain any software on the two reserved tracks. It is intended for use in software distribution.

DATA ONLY FORMAT

9 sectors per track numbered #Cl.. # C9.

0 reserved tracks.

This format is intended for future enhancement, it is not recommended for use with CP/M since it is not possible to 'warm boot' from it. However, if only AMSDOS is to be used then there is a little more disc space available.

IBM FORMAT

8 sectors per track numbered 1..8.

1 reserved track.

This format is logically the same as the single-sided format used by CP/M on the IBM PC. It is intended for specialist use and is not otherwise recommended.

Chapter 5. 5

AMSTRAD Disc Drive & Interface DDI-1 Manual

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Contents Page Amstrad Disc Drive & Interface DDI-1 Amstrad Contents Contents Page Connecting the Mains Lead Foundations 1 Setting UpConnecting the DDI-1 to the Computer Computer Interface Unit Main Disc Drive Drive a Computer Write Protection Foundations 2 About DiscsOpen Closed When Your Disc Is Eject Button Indicator LampROLCAVE. not found Drive a disc missing Retry, Ignore or Cancel?Foundations Loading Software/Games Run rolcaveType mismatch Bad commandSyntax error Drive a read fail Retry, Ignore or Cancel?Foundations Introducing Amsdos and CP/M Tape.in Drive B disc missing Retry, Ignore or CancelLoad filename DiscFirst Steps Using The CP/M Disc Storing Data Onto DiscCpm CLS? Back to Amsdos BewareSaving a Program in Memory onto Disc Catalog Loading From DiscEXAMPLE.BAS Copying Programs From Disc to Disc Copying Programs From Cassette to DiscCopying Programs From Disc to Cassette Copying Using Disccopy Copying Using the CP/M System DiscDo you want to copy another disc Y/N Copying Using CopydiscCopying started Reading track 0 to Writing track 0 toChkdisc Checking DiscsAborting DiscchkInstallation Amstrad Disc Drive & Interface DDI-1 Manual Making Working Discs Backup Master DiscDISCCOPY.COM Working SYSTEM/UTILITY discBasic only disc Turnkey Amstrad Basic discsCreating a Turnkey CP/M System disc Turnkey Basic using disc suppliedTurnkey CP/M Discs Turnkey Basic onto your Working discConfiguring a CP/M Program Configuring the Output from the packageAmbiguous filename Confirm individual files Y/N ? Configuring the Input to the package Starting a Turnkey CP/M PackagePayroll Autostarting a Turnkey CP/M Package Introduction Amsdos PrimerDisc Directory Amsdos filenames and filetypesConstruction of Filenames Amsdos headers Filenames on two drivesSave PROG.BAS a Save Bprog .BAS BERT.BAS FRED1.BAS FRED2.BAS FRED3.BAK FRED3.BAS FINISH.BAS Examples of Using Amsdos Commands in a programWild cards Saving variables and performing a Screen DumpCloseout NeatWend Closein Reference guide to Amsdos commandsPre-empting a Garbage Collection While not EOFCAT Summary of Basic commandsSummary of Amsdos external commands Save OPENOUT, Print #9, Write #9, List #9, CloseoutDISC.IN CPMDIR DiscTAPE.IN ERAREN TapeAscii files File Copying proceduresCopying Files Amsdos files with headersFile has a header Amstrad Reference guide to Amsdos Error Messages Drive Drive write fail Drive Drive disc missingDrive Drive disc is write protected Drive Drive read failCP/M Primer Operating with CP/MCP/M system tracks Configuration Sector Console control codesLogging in a disc ERA command Direct Console CommandsSwitching default drives DIR commandPeripheral Management Transient commandsREN command Type commandCassette files File and disc copyingSingle file copying Whole disc copiers and checkersStat System ManagementIs this correct Y/N SetupDo you want to update your system disc Y/N Stat SECRET.BAS $DIRFormat D Format I Format Disc GenerationAmsdos FormatSysgen BootgenAdvanced programming MovcpmAmstrad Disc Drive & Interface DDI-1 Manual Introduction to Logo What is LogoGetting Started Dr. LogoTo squareanysize side repeat 4 fd side rt 90 end Procedures with parametersRepeat 4 fd 60 rt To square Repeat 4 fd 60 rt 90 endTo triangle Repeat 3 fd edge rt 120 end Using Variables to remember valuesEditing programs and procedures Cs squareanysize 100 rt 45 squareanysizeSummary of Dr. Logo primitives Operating hintsCount Word and List ProcessingAscii CharList EmptypFirst FputArithmetic Operations Logical Operations ?= Logo Logo NotVariables ProceduresShow EditingText Screen SetsplitDot CleanGraphic Screen TypePal SetpalWindow Wrap Turtle GraphicsSetpc SethNodes Workspace ManagementSetpos ErnPlist RecycleGlist GpropKEYBOARD, Joystick buttonp Disc Files DirLoad Save?key Paddle?paddle 0 ?make key rcRelease SoundEnv EntStop LabelRepeat RunThrow ErrorCatch PauseSystem Properties Headers Technical information for the user Firmware Store requirements Changing DiscsError Messages Bios messagesAmsdos messages Failed to load boot sector Common to ALL Formats Disc OrganisationJump Block Interception by Amsdos Jump Block Re-Interception by the UserReturn Parameters Intercepted Firmware Calls 132 #BC8C 133 #BC8F 134 #BC92 135 #BC95 #BC98137 #BC9B Page Appendix Glossary of Terms CP/M Dr.Logo Primitives TPA Amstrad Disc Drive & Interface DDI-1 Manual Appendix Term Limitations of Remedies Amstrad Disc Drive & Interface DDI-1 Manual Appendix Index ERA Setpos