!3SDOS - 3Sector Read-Only DOS
* Assembler: BiboAssembler 1.21
* License: GNU Public License, http://www.gnu.org
* Author: Carsten Strotmann
* Version: 0.8
* Description: Mini-Read-Only DOS 2.x compatible
!! Why?
Why I've written this DOS? I had a BASIC Cassette program. The program consists of two files, ==part1.bas== and ==part2.bas== .
The first part initializes a new character-set and the starts the second part via the CLOAD command.
The second part was really large. Because the cassette load take some time, I would like to have a disk version. But with a normal DOS loaded (MyDOS, ATARI DOS 2.x, 3, DOS XL, Turbo DOS, I tried almost all), there was only some byte free memory left. Too less to run the programm.
So I tested serveral game-dos. (btw, thanks to Matthias Reichl for the new GPL Release of MyPicoDos, http://www.horus.com/~hias/atari/ ). But the game-dos I own don't install a "D:" CIO Handler, they just load the file and start it. That is ok for one-part files, but it didn't work with my two-part file.
So I wrote 3SDOS. It's 384 Bytes long and fits into the first 3 bootsectors. With this, the basic-cassette program works! And it has 4k free space.
!! Limitations:
* only read operations
* "open file" and "get byte" CIO commands
* only finds files in the first directory sector ($169), so only the first 8 directory entries work
* no checks
* slower that normal dos load, but dos starts very fast!
* maybe buggy
!! Future development
* Autoload and Start Basic program in the first Directory entry, for real Basic-Boot-Disks
* keep it in 3 sectors (SD)
!! Download
* See attachments for an empty DOS DISK (SD)
!! FAQ
* How to write the DOS to a new Disk?
* copy sector 1-3 from a 3SDOS Disk to the new Disk
* or, take the source and write a setup program :-)
{{{
00010 .LI OFF
00020 *************************
00030 * *
00040 * 3SECTOR DOS 3SDOS *
00050 * A LOW MEMORY DOS 2.X *
00060 * *
00070 * READ ONLY VERSION *
00080 * *
00090 * (C) 2003 C. STROTMANN *
00100 * LICENSED UNDER GPL *
00110 * *
00120 *************************
00130 ;
00140 ; SIO CONTROL BLOCK
00150 ;
00160 DDEVIC = $0300
00170 DUNIT = $0301
00180 DCMND = $0302
00190 DSTATS = $0303
00200 DBUF = $0304
00210 DTIMLO = $0306
00220 DBYT = $0308
00230 DAUX1 = $030A
00240 DAUX2 = $030B
00250 ;
00260 ; ZERO PAGE REGISTERS
00270 ;
00280 ICHIDZ = $20
00290 ICDNOZ = $21
00300 ICCOMZ = $22
00310 ICSTAZ = $23
00320 ICBADZ = $24
00330 ICBPLZ = $26
00340 ICBBLZ = $28
00350 ICAX1Z = $2A
00360 ICAX2Z = $2B
00370 ICSPRZ = $2C
00380 ICHIDNOZ = $2E
00390 ;
00400 ; FLOPPY SIO COMMANDS
00410 ;
00420 RDSEC = $52
00430 ;
00440 ; SECTOR SIZE
00450 ;
00460 SECSIZ = $80
00470 ;
00480 ; SIO STATUSBYTE
00490 ;
00500 DREAD = $40
00510 ;
00520 ; OS VECTORS
00530 ;
00540 DOSVEC = $0A
00550 DOSINI = $0C
00560 SIO = $E459
00570 CIO = $E456
00580 PHENTV = $E486
00590 BIBOMON = $E471
00600 ;
00610 ; START OF USER MEM
00620 ;
00630 MEMLO = $02E7
00640 ;
00650 ; SCREEN MEM
00660 SAVMSC = $58
00670 ;
00680 ; INIT VECTOR
00690 ;
00700 RUNAD = $02E0
00710 INITAD = $02E2
00720 ;
00730 ; HANDLER TABLE
00740 ;
00750 HATABS = $031A
00760 ;
00770 ; ERROR CODES
00780 ;
00790 ERR_OK = $01 ; NO ERROR
00800 ERR_BRK = $80 ; BREAK KEY
00810 ERR_EOF = $88 ; END OF FILE
00820 ERR_NFND = $AA ; NOT FOUND
00830 ERR_JOPN = $A1 ; JUST OPEN
00840 ;
00850 ; HANDLER CHAR "D:"
00860 HNDCHAR = 'D
00870 ;
00880 ; SECTORS
00890 ;
00900 VTOC = $0168
00910 DIR = $0169
00920 ;
00930 ; BUFFER 128 BYTE
00940 ;
00950 SECBUF = $600
00960 ;
00970 ; FILENAME BUFFER 11 BYTE
00980 ;
00990 FNAME = $100
01000 ;
01010 ORG .OR $700
01020 .OF D:SDOS.COM
01030 ;
01040 DATA
01050 SECCNT = $D4
01060 BUFCNT = $D6
01070 BUFEOF = $D7
01080 DIRCNT = $D7
01090 CURSEC = $D8
01100 DIRP = $DA
01110 ;
01120 ; BOOT HEADER
01130 ;
01140 BOOTH .HX 00
01150 .HX 03 ; 3 SEC DOS
01160 .DA BOOTH ; STORE ADDR
01170 .DA DOSIN
01180 ;
01190 ; SET MEMLO
01200 LDA #PGMEND
01210 STA MEMLO
01220 LDA /PGMEND
01230 STA MEMLO+1
01240 ;
01250 ; SET RESTART VECTOR
01260 LDA #FHINIT
01270 STA DOSVEC
01280 LDA /FHINIT
01290 STA DOSVEC+1
01300 ;
01310 ; BOOTMESSAGE
01320 JSR PMSG
01330 ;
01340 CLC
01350 RTS
01360 ;
01370 ;
01380 ; DOS INI ROUTINE
01390 ;
01400 DOSIN
01410 JSR FHINIT ; INIT HANDLER
01420 RTS
01430 ;
01440 ------------------------------
01450 INIT
01460 FHINIT
01470 LDX #0
01480 .1
01490 LDA HATABS,X
01500 BEQ INSTALL
01510 CMP #HNDCHAR
01520 BEQ INSTALL
01530 INX
01540 INX
01550 INX
01560 CPX #$20
01570 BMI .1
01580 ;
01590 RTS
01600 ------------------------------
01610 ; INSTALL HANDLER
01620 ;
01630 INSTALL
01640 LDA #HNDCHAR
01650 STA HATABS,X
01660 LDA #FHTAB
01670 STA HATABS+1,X
01680 LDA /FHTAB
01690 STA HATABS+2,X
01700 RESETS
01710 LDA #DOSIN
01720 STA DOSINI
01730 LDA /DOSIN
01740 STA DOSINI+1
01750 RTS
01760 ------------------------------
01770 SECRD
01780 LDA #$01 ; DISK 1
01790 STA DUNIT
01800 LDA #$31 ; FLOPPY
01810 STA DDEVIC
01820 LDA #RDSEC ; READ
01830 STA DCMND
01840 LDA #DREAD
01850 STA DSTATS
01860 LDA #SECSIZ
01870 STA DBYT
01880 LDA #0
01890 STA DBYT+1
01900 LDA #SECBUF
01910 STA DBUF
01920 LDA /SECBUF
01930 STA DBUF+1
01940 LDA CURSEC
01950 STA DAUX1
01960 LDA CURSEC+1
01970 STA DAUX2
01980 ;
01990 JSR SIO
02000 ;
02010 LDA SECBUF+$7F
02020 STA BUFEOF
02030 DEC SECCNT
02040 LDA SECBUF+$7D
02050 AND #$03
02060 STA CURSEC+1
02070 LDA SECBUF+$7E
02080 STA CURSEC
02090 LDA #$FF
02100 STA BUFCNT
02110 RTS
02120 ------------------------------
02130 FSPECIAL
02140 FSTATUS
02150 SDOSINIT
02160 FCLOSE
02170 OK LDY ERR_OK
02180 FPUTBYT
02190 RTS
02200 ------------------------------
02210 FOPEN
02220 LDA ICAX1Z ; AUX1
02230 AND #$04 ; READ?
02240 BEQ FCLOSE ;NO WRITE!
02250 LDA #DIR
02260 STA CURSEC
02270 LDA /DIR
02280 STA CURSEC+1
02290 JSR SECRD
02300 LDA #SECBUF
02310 STA DIRP
02320 LDA /SECBUF
02330 STA DIRP+1
02340 LDA #7
02350 STA DIRCNT
02360 ;
02370 ; SEARCH DIR ENTRY
02380 ;
02390 SDIR
02400 LDY #$0F
02410 LDA #$20
02420 .1 STA FNAME,Y
02430 DEY
02440 BPL .1
02450 ;
02460 LDY #0
02470 .2
02480 INY
02490 LDA (ICBADZ),Y
02500 CMP #':
02510 BNE .2
02520 ;
02530 INY
02540 TYA
02550 CLC
02560 ADC ICBADZ
02570 STA ICBADZ
02580 BCC .3
02590 INC ICBADZ+1
02600 .3
02610 LDY #0
02620 LDX #5
02630 .4
02640 LDA (ICBADZ),Y
02650 CMP #'.
02660 BNE .5
02670 LDX #$D
02680 INY
02690 .5
02700 LDA (ICBADZ),Y
02710 STA FNAME,X
02720 INY
02730 INX
02740 CPX #$10
02750 BNE .4
02760 .6
02770 LDY #$F
02780 .7 LDA (DIRP),Y
02790 CMP FNAME,Y
02800 BNE .10
02810 DEY
02820 CPY #4
02830 BNE .7
02840 LDA (DIRP),Y
02850 STA CURSEC+1
02860 DEY
02870 LDA (DIRP),Y
02880 STA CURSEC
02890 DEY
02900 LDA (DIRP),Y
02910 STA SECCNT+1
02920 DEY
02930 LDA (DIRP),Y
02940 STA SECCNT
02950 ;
02960 JSR SECRD
02970 LDY #ERR_OK
02980 RTS
02990 .10
03000 LDA #$10
03010 CLC
03020 ADC DIRP
03030 STA DIRP
03040 BCC .11
03050 INC DIRP+1
03060 .11
03070 DEC DIRCNT
03080 BNE .6
03090 LDY #ERR_NFND
03100 RTS
03110 ;
03120 JMP BIBOMON
03130 ;
03140 ------------------------------
03150 FGETBYT
03160 ; JMP BIBOMON
03170 LDX BUFEOF
03180 BNE .10
03190 JSR SECRD
03200 .10
03210 LDX SECCNT
03220 CPX #$FF
03230 BNE .20
03240 LDY #ERR_EOF
03250 RTS
03260 .20
03270 INC BUFCNT
03280 DEC BUFEOF
03290 LDX BUFCNT
03300 LDA SECBUF,X
03310 JMP OK
03320 ------------------------------
03330 FHTAB
03340 .DA FOPEN-1
03350 .DA FCLOSE-1
03360 .DA FGETBYT-1
03370 .DA FPUTBYT-1
03380 .DA FSTATUS-1
03390 .DA FSPECIAL
03400 JMP SDOSINIT
03410 .DA #0
03420 PGMEND
03430 ------------------------------
03440 MSG
03450 .AT " 3SDOS (c)2003 CST/PSC "
03460 MSGEND .HX 00
03470 ------------------------------
03480 PMSG
03490 LDY #$FF
03500 .1 INY
03510 LDA MSG,Y
03520 STA (SAVMSC),Y
03530 CPY #MSGEND-MSG
03540 BNE .1
03550 RTS
03560 ------------------------------
03570 .OR RUNAD
03580 .DA INIT
03590 ------------------------------
}}}