CP/M ver 1.4 & 2.x Programmer's Reference Guide ======================================================== BUILT-IN COMMANDS ================= DIR Display file directory, current drive DIR d: Display file directory, designated drive DIR filename.typ Search for file name, current drive DIR *.typ Display all files of named type, curr drive DIR filename.* Display all types of designated filename DIR x????.* Display all filenames 5 characters long and starting with letter x TYPE filename.typ Display ASCII file, current drive TYPE d:filename.typ Display ASCII file, designated drive ERA filename.typ Erase named file, current drive ERA *.* Erase all files, curr drv, ver 2.x curr user ERA *.typ Erase all files, current drive ERA d:filename.typ Erase named file, designated drive ERA filename.* Erase all types of named file, current drive REN nuname.typ=olname.typ Rename file, current drive REN d:nuname.typ=olname.typ Rename file, designated drive SAVE n filename.typ Save as named file, current drive SAVE n d:filename.typ Save as named file, designated drive n pages (page = 256 bytes) starting at 100H d: Switch to designated drive, making it current drive V 1.4: A-D V 2.x: A-P USER n Change user area (n=0 to 15) (ver 2.x) TRANSIENT COMMANDS ================== DDT Initiate Dynamic Debugging Tool DDT filename.typ Initiate DDT and load named file ASM filename Assemble named ASM file on current drive ASM d:filename Assemble named ASM file on designated drive ASM filename.abc Assemble named ASM file: a = source file drive b = HEX file destination drive (Z=skip) c = PRN file destination drive (X=console,Z=skip) LOAD filename Make COM file from named HEX file on current drive LOAD d:filename Make COM file from named HEX file on design. drive DUMP filename.typ Display file in hex, current drive DUMP d:filename.typ Display file in hex, designated drive MOVCPM Relocate and execute (max) KByte CP/M system MOVCPM n Relocate and execute n KByte CP/M system MOVCPM n * Create relocated image in RAM of n Kbyte CP/M system, ready for SYSGEN or SAVE MOVCPM * * Create relocated image in RAM of (max) Kbyte CP/M system, ready for SYSGEN or SAVE SYSGEN Initiate SYStem GENerate program SUBMIT filename parameters Execute SUB file using optional parameter(s) XSUB Execute eXtended SUBmit program (V2.x) ED filename.typ Execute EDitor to create or edit named file ED d:filename.typ Execute EDitor to create or edit named file STAT Display STATus (R/W or R/O) \/ current drive STAT d: and available disk space /\ design. drive STAT DEV: Display DEVice assignments STAT VAL: Display VALid device assignments STAT DSK: Display DISK characteristics (V2.x) STAT USR: Display current USeR areas (V2.x) STAT filename.typ $S Display size of file (V2.x) STAT fiename.typ Display file characteristics, current drive STAT d:filename.typ Display file characteristics, designated drive STAT d:=R/O Change designated drive to Read-Only STAT filename.typ $R/O Change named file to Read-Only (V2.x) STAT filename.typ $R/W Change named file to Read-Write (V2.x) STAT filename.COM $SYS Change named file to System file (V2.x) STAT filename.COM $DIR Change named file to Directory file (V2.x) STAT gd:=pd: Change general device (CON:,LST:,PUN:,RDR:) assignment of physical device (IOBYTE) PIP === Commands -------- PIP Initiate Peripheral Interchange Program *d:=s:filename.typ Copy named file from source drive to dest drive *d:nuname.*=s:olname.typ Copy & rename from source drive to dest drive PIP d:=s:filename.typ Initiate PIP and copy named file PIP d:=s:*.* from source drive \/ all files PIP d:=s:filename.* to || all named files PIP d:=s:*.typ destination drive /\ all files named type PIP LST:=filename.typ Send named file to list device PIP PUN:=filename.typ Send named file to punch device PIP CON:=filename.typ Send named file to console device PIP filename.typ=RDR: Copy data from reader device to named file *nuname.typ=aname.typ,bname.typ,cname.typ ASCII copy & concatenate *nuname.typ=aname.typ,bname.typ ASCII copy & concatenate *nuname.typ=aname.typ[X],bname.typ[X] binary copy & concatenate PIP LST:=aname.typ,bname.typ Send files in sequence to list device PIP LST:=s:aname.typ,s:bname.typ Send files in sequence to list device PIP allows access to any logical and physical devices defined in the CP/M system. Logical devices: CON: RDR: PUN: LST: Physical devices: TTY: CRT: PTR: UR1: UR2: PTP: UP1: UP2: LPT: UL1: Special PIP devices (locations 109H to 1FFH are not used in the PIP image and can be replaced by used drivers using DDT) NUL: Send 40 NUL's (ASCII 00H) to the device (can be issued at the end of punched output) EOF: Send a CP/M EOF (ASCII Ctrl-Z=1AH) to dest device (sent automatically at end of ASCII transfers thru PIP) INP: Special PIP input source which can be patched into PIP: PIP gets input from here by calling 103H, with data returned at 109H) OUT: Special PIP output destination which can be patched into PIP: PIP calls 106H with data to be output in C for each char. PRN: Same as LST: except that tabbs are expanded to every 8th column, lines are numbered, and page ejects are inserted every 60 lines with an initial eject (same as PIP options [t8np]) Parameters ---------- example *filename.typ=RDR:[B] [B] - read data block until ^S (ctrl-S) character [Dn] - delete characters past column n [E] - echo all copy operations to console [F] - remove form feeds [Gn] - get file from user area n (V2.x) [H] - check for proper HEX format [I] - same as H plus ignores ":00" [L] - change all upper case characters to lower case [N] - add line numbers without leading zeros [N2] - same as N plus leading zeros and a TAB after number [O] - object file transfer; ignore end-of-file (Ctrl-Z) [P] - insert form feed every 60 lines [Pn] - insert form feed every n lines [Qstring^Z] - Quit copying after string is found [R] - read SYS file (V2.x) [Sstring^Z] - Start copying when string is found [Tn] - expand tab space to every n columns [U] - change all lower case characters to upper case [V] - verify copied data (destination must be disk file) [W] - delete R/O files at destination (V2.x) [X] - copy non-ACII files [Z] - zero parity bit (hi bit) on all characters in file Keywords -------- CON: CONsole device (defined in BIOS) EOF: send End-of-File (ASCII ^Z) to device INP: INPut source (pathced in PIP) LST: LiST device (defined in BIOS) NUL: send 40 NUL's to device OUT: OUTput destination (pathced in PIP) PRN: same as LST:; tabs every 8th char, number lines & page ejects every 60 lines with initial eject PUN: PUNch device (defined in BIOS) RDR: ReaDeR device (defined in BIOS) COMMAND CONTROL CHARACTERS ========================== Control char ASCII code Function C 03h Reboot - CP/M warm boot E 05h Start new line H 08h Backspace and delete (V2.x) I 09h Tab 8 columns J 0Ah Line feed M 0Dh Carriage return P 10h Printer on/Printer off R 12h Retype current line S 13h Stop display outout (any char except ^C restarts) U 15h Delete line X 18h Same as Û (V1.4) Z 1Ah End of console input (ED & PIP) delete/rubout 7Fh Delete and display character (tape only) ASM === Conventions ----------- line# label operation operant ;comment labels followed by colon 1-16 alphanumeric characters symbol (eq. EQU) no colon first must be alpha, ? or . labels are case insensitive (treated as uppercase) $ is insignificant and can be inserted anywhere for readability Assembly Program Format (space separates fields) [line#] label: opcode oerand(s) ;comment Constants A number of digits with a suffix: B binary O or Q octal D decimal (default) H hexadecimal Reserved words in operand fields The names of the 8080 registers are reserved, and produce the following values if encountered in the operand field: A 7 B 0 C 1 D 2 E 3 H 4 L 5 M 6 SP 6 PSW 6 Mnemonics for machine instructions are reserved and evaluate to their internal codes. Instructions which require operands will get zeroes in their operand fields, e.g. MOV will produce 40H The symbol $ in the operand field evaulates to the address of the next instruction to generate, not including the instruction within the current logical line String constants are delimieted by an apostrophe ('), and a double apostrophe ('') will produce one apostrophe Operators (unsigned) a+b a added to b a-b difference between a and b +b 0+b (unary addition) -b 0-b (unary subtraction) a*b a multiplied by b a/b a divided by b (integer) a MOD b remainder after a/b NOT b complement all b-bits a AND b bit-by-bit AND of a and b a OR b bit-by-bit OR of a and b a XOR b bit-by-bit XOR of a and b a SHL b shift a left b bits, end off, zero fill a SHR b shift a right b bits, end off, zero fill Hierarcy of operations highest: * / MOD SHL SHR - + NOT AND OR XOR Pseudo-ops ORG const Set program or data origin (Default=0) END start End program, optional address where excution begins EQU const Define symbol value (may not be changed) SET const Define symbol value (may be changed later) IF const Assemble block conditionally until ENDIF ENDIF Terminate conditionala ssembly block DS const Define storage sace for later use DB byte[,byte...] Define bytes as numeric or ASCII constants DW word[,word...] Define words (two bytes) const=constant (true if bit 0 is 1, otherwise false) Error codes ----------- D Data error (element cannot be placed in data area) E Expression error (ill-formed expression) L Label error N Not implemented O Overflow (expression too complicated to compute) P Phase error (label has different values on each pass) R register error (specified value not compatible with op code) U Undefined label (label does not exist) V Vaue error (operand improper) Fatal errors ------------ NO SOURCE FILE PRESENT NO DIRECTORY SPACE SOURCE FILE NAME ERROR SOURCE FILE READ ERROR OUTPUT FILE WRITE ERROR CANNOT CLOSE FILE FILE TYPES ========== ASC ASCII text file, usually Basic source ASM ASseMbly langaige file (source for ASM program) BAK BAcKup copy file (created by editor) BAS BASic source program file, usually tokenized COM COMmand file (transient exeuctable program) DAT DATa file DOC DOCument file FOR FORtran source program file INT INTermediate Basic program file (executable) HEX HEXadecimal format file (for LOAD program) LIB Library file used by macro assembler PLI PL/I source file PRN PRiNt file (source and object produced by ASM) REL RELocatable file SAV System file (V2.x) SUB SUBmit text file executed by SUBMIT program SYM SID symbol file TEX TEXt formatter source file XRF Cross reference file $$$ Temporary file Filename - 8 characters maximum Filetype - 3 characters maximum Invalid filename and filetype characters < > . , ; : = ? [ ] DDT COMMANDS ============ DDT DDT filename.HEX DDT filename.COM A sad Assemble symbolic code; start at sad D Dump RAM to console from cad, 16 lines D sad Dump RAM to console from sad, 16 lines D sad,ead Dump RAM to console from sad thru ead F sad,ead,const Fill RAM from sad thru ead with const G Start program exec. at saved PC G sad Start program exec. at sad G sad,bp1 Start program exec. at sad and stop at bp1 G sad,bp1,bp2 Start program exec. at sad and stop at bp1 or bp2 G,bp1,bp2 Start program exec. at cad and stop at bp1 or bp2 G0 Jump to 0000H ==> exits DDT (equivalent to Ctrl-C) H a,b Display hex a+b and a-b I filename Set up FCB at 5CH for user code I filename.typ Set up FCB at 5CH for R-command (HEX or COM file) L Disassemble RAM from cad, 12 lines L sad Disassemble RAM from sad, 12 lines L sad,ead Disassemble RAM from sad thru ead M sad,ead,nad Move RAM block from sad thru ead to nad R Read file specified by I command to RAM R offset at normal address + optional offset The R command requires a previos I command There is no W (write file) command, instead exit DDT (by G0 or Ctrl-C) and then use SAVE S sad Examine and optionally alter RAM, byte by byte, starting at sad T Trace: execute 1 instruction with register dump T n Trace: Execute n instructions with register dump U Untrace: same as T except that intermediate U n steps are not displayed X Examine register or flags, display format: CfZfMfEfIf A=bb B=dddd D=dddd H=dddd S=dddd P=dddd inst Xr Examine/change registers or flags C Carry flag (0/1) Z Zero flag (0/1) M Sign flag (0/1) E Parity flag (0/1) I Aux Carry flag (0/1) A Accumulator (0-FF) B BC reg pair (0-FFFF) D DE reg pair (0-FFFF) H HL reg pair (0-FFFF) S Stack Pointer (0-FFFF) P Program Counter (0-FFFF) cad = current address nad = new address sad = start address ead = end address ? = error, can mean: file cannot be opened checksum error in HEX file assembler(disassembler overlayed ED COMMANDS =========== nA Append n lines to buffer (n=0 - use haf of buffer) B Move pointer to beginning of file -B Move pointer to end of file nC Move pointer forward n characters nD Delete n characters forward E End edit, close file, return to CP/M nFs Find n'th occurence of string 's' H End edit, move pointer to beginning of file I Insert text at pointer until ^Z typed Is Insert string at pointer nK Kill n lines starting at pointer nL Move pointer n lines nMx Execute command string 'x' n times nNs Global F-command - until end of file O Abort ED, start over with original file nP List next n pages of 23 lines (n=0 - current page) Q Quit without changing input file Rfn Read fn.LIB into buffer at current pointer nSx^Zy Substitute string 'y for next n forward occurrences of string 'x' nT Type n lines U Change lower case to upper case (next entry) V Enable internal line number generation nW Write n lines to output file, start at beginning of buffer nX Write next n lines to file 'X$$$$$$$.LIB' nZ Pause n/2 seconds (2 MHz) n Move forward n lines Move forward one line and type one line - Move backward n:x Move to n line number and perform 'x' command :mx Perform command 'x' from current line to line m n::mx Move to n line number and perform command 'x' from current line to line m note: "-" valid on all positioning and display commands for backward movement (e.g. -nC) HOW TO OPEN UP A NEW USER AREA ============================== Enter PIP wait for the * prompt. Hit Return to go back to exit PIP. Now, enter the user area, say USER 1. Type SAVE 28 PIP.COM and hit Return (SAVE 30 PIP.COM in CP/M 3). Now, PIP.COM is in your new user area, and you can copy any file into your area from area 0 by typing PIP A:=[G0] and Return. PATCHING THE CCP TO PERFORM ONE COMMAND AT EVERY WARM BOOT ========================================================== The CCP stars with the instructions: JMP CCPSTART ; Start the console processor JMP CCPCLEAR ; Clear the initial command DB 127 ; Maximum command length CL: DB 0 ; Current command length DB ' ' ; 8 spaces DB ' ' ; 8 more spaces DB 'COPYRIGHT... ; Copyright notice Starting at CL, patch in the command, e.g.: CL: DB 3 ; Current command length DB 'DIR',0 ; DIR command, NUL terminated DB ' ' ; 4 spaces DB ' ' ; 8 more spaces DB 'COPYRIGHT... ; Copyright notice and add this to the CCP image on the system tracks of your disk (using MOVCPM, DDT and SYSTEM on most CP/M systems, or DDT amd CPM56K.COM or CPM60K.COM on Apple CP/M). Now, after every warm boot the CCP will execute this command (in this example a 'DIR' command) BDOS FUNCTION CALLS =================== Function no Value passed to BDOS Value returned in in C reg in DE (or E) regs A or HL regs Dec Hex 0 00 System reset -- -- 1 01 Console read -- A = char 2 02 Console write E = char -- 3 03 Reader read -- A = char 4 04 Punch write E = char -- 5 05 List write E = char -- 6 06 Direct console I/O E = FFh (input) A = char (V2.x) E = char (output) -- 7 07 Get IOBYTE -- A = IOBYTE 8 08 Set IOBYTE E = IOBYTE -- 9 09 Print string DE = string addr -- string terminated by $, tabs are expanded as in func 2 10 0A Read console buffer DE = buffer addr A = #chars in buffer buffer: 1st byte = bufsize, 2nd byte = chars input 11 0B Get console status -- A = 00(not rdy)/FF(rdy) 12 0C Lift head (V1.x) -- -- Get version (V2.x) -- HL = version no H: 0=CP/M, 1=MP/M L: 0=v1.4 20H-22H=v2.x 13 0D Reset disk** -- -- 14 0E Select disk E = drive no -- 0=A, 1=B, ...0FH=P 15 0F Open file DE = FCB addr A = dir code 16 10 Close file DE = FCB addr A = dir code 17 11 Search for first DE = FCB addr A = dir code 18 12 Search for next -- A = dir code 19 13 Delete file DE = FCB addr A = dir code 20 14 Read sequential DE = FCB addr A = ret code 21 15 Write sequential DE = FCB addr A = ret code 22 16 Create file DE = FCB addr A = dir code 23 17 Rename file DE = old FCB addr A = dir code 24 18 Get login vector -- (V1.4) HL = drive code 25 19 Get disk no -- A = curr disk no (0-15 for A-P) 26 1A Set DMA addr DE = DMA addr -- 27 1B Get alloc vector -- HL = ava 28 1C Write protect disk -- -- 29 1D Get R/O vector -- HL = R/O vect 30 1E Set file attrib DE = FCB addr A = dir code 31 1F Get addr disk params -- HL = dpba 32 20 Set user code E = user code -- 32 20 Get user code E = FFh A = curr user code 33 21 Read random DE = ext. FCB addr A = ret code *** 34 22 Write random DE = ext. FCB addr A = ret code *** 35 23 Compute file size DE = ext. FCB addr A = ret code 36 24 Set random record DE = ext. FCB addr A = ret code 37 25 Reset drive DE = drive vector A = 0 38 26 (unused) -- -- 39 27 (unused) -- -- 40 28 Write random DE = FCB addr A = ret code *** with zero fill dir code: directory code: 0FFH=failed (e.g. file not found, directory full) 0,1,2,3 = success: offset into current DMA buffer, which contains a directory sector, where the FCB can be found ret code: return code -- 0=success, non-zero=failed * V1.4 none ** V1.4 initializes system and selects A: drive *** ret codes: 00 - no error 01 - reading unwritten data 03 - cannot close current extent 04 - seek to unwritten extent 05 - directory overflow (write only) 06 - seek past physical end of disk char = ASCII character addr = address dir = directory code cdn = current drive number (A=0, B=1, etc) dpba = disk parameter block address in CBIOS Function 9: string is terminated with '$' Function 10: Console buffer: 1st byte = max # chars in buffer (input) 2nd byte = actual # chars in buffer (output) remaining bytes = buffer Function 12: CP/M version number: H=00 CP/M, H=01 MP/M L=00 ver prior to 2.0 L=20,21,22... subsequent versions Function 13: Resets DMS address to BOOT+0080h Function 23: renames file in first 16 bytes of FCB to name in second 16 bytes in FCB Function 24: Returns a 16-bit value in HL - a 16-bit bit map where the lowest bit represents A: and the highest bit P: If the bit is set, that drive is present in the CP/M system Function 29: Returns a similar bit map as func 24, except that a set bit marks a drive which is Read/Only. Function 33,34: the rn (Random Record No) must be set in the FCB prior to call Function 35: fills in the file size in rn. If followed by a random write, the file will be extended in length. Not that the "file size" merely is the last record # - "hole" in sparse files are not accounted for Function 36: same as function 35 except that the current random record position is stored in rn in FCB. Function 37: this function is buggy - avoid using it IOBYTE (0003H) ============== Device LST: PUN: RDR: CON: Bit position 7 6 5 4 3 2 1 0 Dec Binary 0 00 TTY: TTY: TTY: TTY: 1 01 CRT: PTP: PTR: CRT: 2 02 LPT: UP1: UR1: BAT: 3 03 UL1: UP2: UR2: UC1: TTY: TeleTYpe CRT: Cathode Ray Tube type terminal BAT: BATch process (RDR=inut, LST=output) UC1: User defined Console LPT: Line Printer UL1: User defined List device PTR: Paper Tape Reader UR1: User defined Reader device 1 UR2: User defined Reader device 2 PTP: Paper Tape Punch UP1: User defined Punch device 1 UP2: User defined Punch device 2 LOGIN BYTE (0004H) ================== low nibble = current drive (0=A, 1=B, etc) high nibble = current user (V2.x only) BIOS ENTRY POINTS ================= Hex Vector Function Value Value addr name passed returned 4A00H+b BOOT Cold start entry point - C=0 4A03H+b WBOOT Warm start entry point - C=drv no 4A06H+b CONST Check for console ready - A=const 4A09H+b CONIN Read from console - A=char 4A0CH+b CONOUT Write to console C=char - 4A0FH+b LIST Write to list device C=char - 4A12H+b PUNCH Write to punch device C=char - 4A15H+b READER Read from reader device - A=char 4A18H+b HOME Move head to track 0 - - 4A1BH+b SELDSK Select drive C=drv no HL=dph*, HL=0 for error 4A1EH+b SETTRK Set track number BC=trk no - 4A21H+b SETSEC Set sector number BC=sec no - 4A24H+b SETDMA Set DMA address BC=DMA - 4A27H+b READ Read selected sector - A=dskst 4A2AH+b WRITE Write selected sector - A=dskst 4A2DH+b* LOSTST Get list status - A=lstst 4A30H+b* SECTRAN Sector translate BC=lsecno HL=physec DE=smap BOOT: gets control after the cold start loader Basic system initalization Send sign-on message Set IOBYTE Set the WBOOT parameters Jump to CCP at its entry point (at its first address 3400H+b) WBOOT: gets control after Ctrl-C or JP 0000 or CPU reset Reload CP/M CCP and BDOS Setup JMP WBOOT at 0000H-0002H (JMP 4A03H+b) Set inital value of IOBYTE at 0003H Set 0004H hi nibble = current user no, lo nibble = current drive no Setup JMP BDOS at 0005H-0007H (JMP 3C06H+b) Set C=current drive, then branch to CCP at 3400H+b const = console status: 00=idle, FF=data avail dph = disk parameter/header address dskst = disk status: 00=OK, 01=error lstst = list status: 00=busy, FF=ready lsecno = logical sector number \ physec = physical sector number | (standard skew factor = 6) smap = sector interlace map address / char = 7-bit ASCII char with parity bit (=hi bit) zero drv no = drive number: 0=A, 1=B, etc, max 15=P trk no = track number (0-76 std CP/M floppy, 0-65535 non-standard) sec no = sector number (1-25 std CP/M floppy, 1-65535 non-standard) DMA = DMA address (default 0080H) * = not used in V1.4 ** = contents of location 0002Hz FILE CONTROL BLOCK (FCB) ======================== Byte Function offset 0 dr Drive code (0=current, 1=A, 2=B, ...., 16=P) 1-8 f1-f8 File name, hi but = 0 9-11 t1-t3 File type + status (hi bits) t1: 1=R/O t2: 1=SYS t3: 1=archived 12 ex Current extent number 13 s1 reserved (V1.4: not used) 14 s2 =0 on BDOS call to Open/Make/Search (v1.4: always 0) 16 rc extent record count: 0-127 16-31 d0-dn Disk map 32 cr Current record for R/W 33-35 rn Random record number, 0-65535, overflow into 3rd byte MEMORY ALLOCATION ================= V1.4: b = memsize-16K 0000 - 00FF System scratch area 0100 - 28FF+b TPA (Transient Program Area) - COM file area 2900+b - 30FF+b CCP - Console COmmand Processor 3100+b - 3DFF+b BDOS 3E00+b - 3FFF+b CBIOS V2.2: b = memsize-20K 0000 - 00FF System scratch area 0100 - 33FF+b TPA (Transient Program Area) - COM file area 3400+b - 3BFF+b CCP - Console COmmand Processor 3C00+b - 49FF+b BDOS 4A00+b - 4FFF+b CBIOS System scratch area, "page zero": 00 - 02 Jump to BIOS warm start entry point 03 IOBYTE 04 Login byte: Login drive number, current user number 05 - 07 Jump to BDOS 08 - 37 Reserved; interrupt vectors & future use 38 - 3A RST7 - used by DDT and SID programs, contains JMP into DDT/SID 3B - 3F Reserved for interrupt vector 40 - 4F Scratch area for CBIOS; unused by distribution version of CP/M 50 - 5B Not used, reserved 5C - 7C Default FCB (File Control Block) area 7D - 7F Optional Default Random Record Position (V2.x) 80 - FF Default DMA buffer area (128 bytes) for disk I/O Also filled with CCP commandline at the start of a program CP/M STANDARD DISK FORMAT (8" SSSD) =================================== Media: 8" soft-sectored floppy-disk single density (IBM 3740 standard) Tracks: 77, numbered 0 thru 76 Sectors/track: 26 (numbered 1 thru 26) Bytes/sector: 128 data bytes (one logical record) Storage/disk: 256256 bytes (77*26*128) File size: any number of sectors from zero to capacity of disk Extent: 1 kBytes - 8 sectors (smallest file space allocated) Skew: 6 sectors standard (space between consecutive physical sectors on track): 1-7-13-19-25-5-11-17-23-3-9-15-21-2-8-14-20-26-6-12-18-24-4-10-16-22 System: Track 0 & 1 (optional) Track 0 sector 1: boot loader Track 0 sectors 2-26: CCP & BDOS Track 1 sectors 1-17: CCP & BDOS Track 1 sectors 18-26: CBIOS Directory: Track 2: 16 sectors typical 32 bytes/entry 64 entries typical extents 0 and 1 User file area: Remaining sectors on Track 2 and 3 to 76, extents 2 and above A Standard CP/M 8" SSSD floppy contains: Track# Sector# Page# Mem address CP/M module name 00 01 (boot addr) Cold start loader 00 02 00 3400H+b CCP 00 03 . 3480H+b CCP 00 04 01 3500H+b CCP 00 05 . 3580H+b CCP 00 06 02 3600H+b CCP 00 07 . 3680H+b CCP 00 08 03 3700H+b CCP 00 09 . 3780H+b CCP 00 10 04 3800H+b CCP 00 11 . 3880H+b CCP 00 12 05 3900H+b CCP 00 13 . 3980H+b CCP 00 14 06 3A00H+b CCP 00 15 . 3A80H+b CCP 00 16 07 3B00H+b CCP 00 17 . 3B80H+b CCP 00 18 08 3C00H+b BDOS 00 19 . 3C80H+b BDOS 00 20 09 3D00H+b BDOS 00 21 . 3D80H+b BDOS 00 22 10 3E00H+b BDOS 00 23 . 3E80H+b BDOS 00 24 11 3F00H+b BDOS 00 25 . 3F80H+b BDOS 00 26 12 4000H+b BDOS 01 01 . 4080H+b BDOS 01 02 13 4100H+b BDOS 01 03 . 4180H+b BDOS 01 04 14 4200H+b BDOS 01 05 . 4280H+b BDOS 01 06 15 4300H+b BDOS 01 07 . 4380H+b BDOS 01 08 16 4400H+b BDOS 01 09 . 4480H+b BDOS 01 10 17 4500H+b BDOS 01 11 . 4580H+b BDOS 01 12 18 4600H+b BDOS 01 13 . 4680H+b BDOS 01 14 19 4700H+b BDOS 01 15 . 4780H+b BDOS 01 16 20 4800H+b BDOS 01 17 . 4880H+b BDOS 01 18 21 4900H+b BDOS 01 19 . 4980H+b BDOS 01 20 22 4A00H+b BIOS 01 21 . 4A80H+b BIOS 01 22 23 4B00H+b BIOS 01 23 . 4B80H+b BIOS 01 24 24 4C00H+b BIOS 01 25 . 4C80H+b BIOS 01 26 25 4D00H+b BIOS 02 01-08 Directory block 1 02 09-16 Directory block 2 02 17-26 Data 03-76 01-26 Data DISK PARAMETER TABLES ===================== Each disk drive has an associated 16-byte (8-word) DPH - Disk Parameter Header, containing: Offset Contents ------ -------- 00H XLT Addr of logical-to-physical sector translation vector or 0000H of no translation (i.e. they are the same) Disk drives with identical sector skew factors share the same table 02H 0000H \ 04H 0000H | Scratchpad values for use within BDOS 06H 0000H / (initial value unimportant) 08H DIRBUF Addr of scratchpad 128-byte directory buffer. All DPH's share the same DIRBUF. 0AH DPB Addr of Disk Parameter Block for this drive 0CH CSV Addr of scratchpad area used for software check for changed disks. Each DPH has its own CSV. 0EH ALV Addr of scratchpad area used for disk storage allocation information. Each DPH has its own ALV. If the system has n disk drives, the n DPH's are arranged one after another, from drive 0 to drive n-1, starting at DPBASE: DPBASE: +--------+------+------+------+--------+--------+--------+--------+ 00 | XLT 00 | 0000 | 0000 | 0000 | DIRBUF | DPB 00 | CSV 00 | ALV 00 | +--------+------+------+------+--------+--------+--------+--------+ 01 | XLT 01 | 0000 | 0000 | 0000 | DIRBUF | DPB 01 | CSV 01 | ALV 01 | +--------+------+------+------+--------+--------+--------+--------+ ...................................................................... +--------+------+------+------+--------+--------+--------+--------+ n-1 | XLTn-1 | 0000 | 0000 | 0000 | DIRBUF | DPBn-1 | CSVn-1 | ALVn-1 | +--------+------+------+------+--------+--------+--------+--------+ The SELDSK subroutine is responsible for returning the base address of the DPH for the selected drive, or 0000H if there is no such drive: NDISKS EQU 4 ; Number of disk drives ......... SELDSK: ; Select disk given by BC LXI H,0000H ; Error return MOV A,C ; Drive OK? CPI NDISK ; Carry if so RNC ; Return if error ; No error, continue MOV L,C ; Low (disk) MOV H,B ; Hi (disk) DAD H ; *2 DAD H ; *4 DAD H ; *8 DAD H ; *16 LXI D,DPBASE ; First DPH DAD D ; DPH(disk) RET The translation vectors (XLT 00 thru XLTn-1) are located elswehere in the BIOS and simply correspond one-for-one with the logical sector number zero through the sector count. The Disk Parameter Block (DPB) for each drive type contains: Offset Contents ------ -------- 00H SPT 16b Total number of sectors per track 02H BSH 8b Data allocation block shift factor, determined by the data block allocation size 03H BLM 8b Data allocation block mask (2[BSH-1]) 04H EXM 8b Extent mask, determined by data block allocation size and number of disk blocks 05H DSM 16b Total storage capacity of disk drive 07H DRM 16b Total number of directory entries minus one 09H AL0 8b Determines reserved directory blocks 0AH AL1 8b Determines reserved directory blocks 0BH CKS 16b Size of directory check vector 0DH OFF 16b No of reserved tracks at beginning of logical disk 0FH (end of table) BSH and BLM are determined by BLS, the block size or data allocation size BLS BSH BLM EXM ----- --- --- DSM<256 DSM>=256 1024 3 7 0 n/a 2048 4 15 1 0 4096 5 31 3 1 8192 6 63 7 3 16384 7 127 15 7 i.e. BLS = 2**n where n = 10 to 14 BSH = n-7 BLM = 2**BSH - 1 EXM = 2**(BHS-2) - 1 if DSM<256 EXM = 2**(BHS-3) - 1 if DSM>=256 DSM = maximum data block number supported by this particular drive, measured in BLS (BLock Size) units, or simply "number of allocation blocks on drive". Blocks are counted from 0 to DSM, and thus BLS*(DSM+1) = the number of bytes on the drive (excluding the system tracks). If DSM<256, the disk map in the directory entry of the file will be 1 byte/block. If DSM>=256 it will be 2 bytes/block. DRM = total number of directory entries minus one. AL0/AL1 = the directory allocation vector. Consider it a bit map of bits 16 bits, bit 0-15, where 0=hi bit of AL0, 7=lo bit of AL0, 8=hi bit of AL1, 15=lo bit of AL1. Bits are assigned starting at bit 0 up until bit 15. Suppose nbits is the number of bits seet to 1: BLS Directory entries --- ----------------- 1024 32 * nbits 2048 64 * nbits 4096 128 * nbits 8192 256 * nbits 16384 512 * nbits Example: if DRM=127 (128 directory entries) and BLS=1024 bytes, there are 32 directory entries per block, requiring 4 reserved blocks. Thus the 4 hi bits if AL0 are set, and AL0=0FH, AL1=00H CKS = size of directory check vector If drive media is removable, then CKS = (DRM+1)/4 If drive media is fixed, then CKS=0 (no dir records checked) OFF = number of reserved tracks. This value is automatically added whenever SETTRK is called. It can be used to skip reserved system tracks, or for partitioning a large disk into smaller segmented sections. Several DPH's can address the same DPB if the drive characteristics are identical. The DPB can be dynamically changed when a new drive is addressed by simply changing the pointer in the DPH since the BDOS copies the DPB values to a local area whenever the SELDKS function is invoked. The size of the CSV (scratchpad area to check changed disks) is CKS bytes. If CKS=(DRM+1)/4, this area must be reserved. If CKS=0, no storage is reserved. The size of the ALV (scratchpad area for disk storage allocation info) is (DSM/8)+1 bytes where DSM is the disk size in allocation blocks. DISK PARAMETER TABLES FOR SPECIFIC DISKS ======================================== Standard CP/M 8" SSSD disk -------------------------- 128 bytes/sector 26 sectors/track 77 tracks - 2 system tracks 75 used tracks ==> 243.75 user KBytes/disk 1024 bytes/block ==> 243 blocks/disk ==> DSM=242 Directory in 2 first blocks ==> 64 directory entries ==> 241.75 KBytes data Sector skew table (1 byte/sector): 1, 7, 13, 19, 25, 5, 11, 17, 23, 3, 9, 15, 21, 2, 8, 14, 20, 26, 6, 12, 18, 24, 4, 10, 16, 22 DPB SPT 16b 26 Sectors per track BSH 8b 3 Block shift factor BLM 8b 7 Block shift mask EXM 8b 0 Extent mask - null DSM 16b 242 Disk size - 1 (in blocks) DRM 16b 63 directory mask = dir entries - 1 AL0 8b 0C0H Dir Alloc 0 AL1 8b 0 Dir Alloc 1 CKS 16b 16 Directory check vector size OFF 16b 2 Track offset: 2 system tracks Dirbuf 128 bytes ALV 31 bytes CSV 16 bytes Block size 1024 bytes ==> BSH=3, BLM=7 DSM = 242 blocks Disk size: 243.75 KBytes excluding system tracks 250.25 KBytes including system tracks Apple CP/M 5.25" disks ---------------------- Physical format: A B C ---- Standard ----- ----- Special ------ 13-sect 16-sect 80-trk/16-sec/2-side Bytes/sector 256 256 256 Sectors/track 13 16 16 Tracks 35 35 80 Heads 1 1 2 Sector skew table (1 byte/sector): no sector skew in CP/M BIOS 13-sector disks: hard sector skew 16-sector disks: soft sector skew in 6502 code (CP/M RWTS) DPB A B C SPT 16b 26 32 32 Sectors per track BSH 8b 3 3 4 Block shift factor BLM 8b 7 7 15 Block shift mask EXM 8b 0 0 0 Extent mask DSM 16b 103 127 313 Disk size - 1 (in blocks) DRM 16b 47 63 255 Directory mask = dir entries - 1 AL0 8b 0C0H 0C0H 0F0H Dir Alloc 0 AL1 8b 0 0 0 Dir Alloc 1 CKS 16b 12 16 64 Directory check vector size OFF 16b 3 3 3 Track offset: 3 system tracks Block size 1024 1024 2048 Dir entries 48 64 256 Dir blocks 2 2 4 DSM+1 104 128 314 blocks Disk size 104 128 628 KBytes (excluding system tracks) 113.75 140 640 KBytes (including system tracks) Dirbuf 128 128 128 bytes ALV 14 17 40 bytes CSV 12 16 64 bytes