;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ ;ญ -> DiskBOOTloader <- ญ ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ ;ญ 1990 by Duke/Level Four ญ ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ ;Notes: ;a) If you want to load and execute CRUNCHED proggys with this ; loader, you should know the address where the decruncher puts ; your program into memory to be sure that it won't scratch the ; loader-routine. Moreover you have to know that your prog ; will crash if you load it into its own decrunch area! ; To prevent such crashes, you're able to set the address ; of the bootloader and the address where your prog should ; be located after loading by changing the address at ; "Bootstart". !!!DON'T DECREASE THE OFFSET AT "Buffer"!!! ;b) How to install the bootloader on your disk (df0:): ; 1. assemble this loader (with MASTERSEKA) ; 2. bstart_boot ;calculate boot-checksum ; 3. ws0 ;(w)rite(s)ector on df(0) ; 4. BEG>start_boot ; 5. SECTOR>0 ;start sector 0 ; 6. AMOUNT>2 ;write 2 sectors (1024 bytes) ; Now you must save the program which you want to load to the ; same disk on the correct tracks. You can do that with ; MASTERSEKA, too, by typing: ; 1.ri ;(r)ead (i)mage ; 2.FILENAME>progname ;enter name of your program here ; 3.BEG>$40000 ;load prog. to $40000 for example ; 4.END> ;load WHOLE prog. just return here ; 5.wt0 ;(w)rite (t)rack on df(0) ; 6.BEG>$40000 ; 7.CYLINDER>enter startcylinder here (1 cylinder=2 tracks) ; 8.AMOUNT>enter length of your prog in cylinders (1cyl=11264bytes) ;If you have no MASTERSEKA you can use the Amiga Mon or the C-mon ;to install your program and the loader on disk. ;Ok. Now your AMIGA should load and execute your program correctly. ;signed duke/l4 ;ญญญญญญญญญญญญญญMACRO-definitionsญญญญญญญญญญญญญญญญญญ color: macro move.w #\1,$180(a6) endm ;now we waste diskspace by using the following step-macro (but who ;cares ? - This bootblock is about 920 bytes long...) step: macro move.b floppystatus(pc),d0 move.b d0,d1 bclr #0,d0 ;clear DSKSTEP after setting it...STEP! move.b d0,(a0) ;a0=$bfd100 (CIA-B PRB) nop ;wait a little nop move.b d1,(a0) ;set DSKSTEP back to 1 bsr.l timer ;wait a while endm ;ญญญญญญญญญญญญญญญญญStatementsญญญญญญญญญญญญญญญญญญญญญญ Bootstart = $20000 ;ญbootstart=address of bootloader - may be changed!ญ ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ Buffer = Bootstart+$4000 ;ญbuffer=address of your decoded program - !!!DON'T DECREASE IT!!!ญ ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ Amount = 22 ;ญamount of tracks to read - may be changed, of course! first_track = 26 ;ญfirst track to read - may be changed, too! ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ org $40000 ;$40000 should work without 1MB, too. load $40000 start_boot: dc.b "DOS",0 ;DOS id dc.l 0 ;space for checksum dc.l $370 ;pointer to rootblock ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ movem.l d0-d7/a0-a6,-(a7) lea bootstart,a0 ;copy bootblock to bootstart (s. above) lea start_boot(pc),a1 move.w #$ff,d7 ;copy 1024 bytes copy_boot: move.l (a1)+,(a0)+ dbf d7,copy_boot jmp bootstart+[start-start_boot] ;jump in loader ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ ;Here the loading-routine... S: Start: lea $dff000,a6 ;coustom base lea s(pc),a5 ;addressoffset (bootblock MUST be pc- ;relative) move.w $01c(a6),oldint-s(a5) ori.w #$8000,oldint-s(a5) move.w $002(a6),olddma-s(a5) ori.w #$8000,olddma-s(a5) move.w $010(a6),oldadk-s(a5) ori.w #$8000,oldadk-s(a5) move.w #$7fff,d0 move.w d0,$096(a6) ;switch dma's off move.w d0,$09a(a6) ;forbid interrupts move.w d0,$09c(a6) ;clear intreq move.w d0,$09e(a6) ;clear adkcon color 0 ;background color while loading move.w #$8210,$96(a6) ;diskdma on! ;select DRIVE: 3210 moveq #%0001,d0 ;set right bit for drive 0,1,2 or 3 bsr.l select_drive ;select drive from which you want to read bsr.l motor_on ;drivemotor on moveq #0,d0 ;move track number ->d0 bsr.l head_pos ;move head to track 0 (orientation) bsr.l init_read ;init diskregisters ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ move.w #Amount,trackct-s(a5);set trackcounter ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ Load_tracks: bchg #1,$bfe001 ;switch led on/off each cylinder move.w track(pc),d0 ;move head to starttrack bsr.l head_pos bsr.l test_disk ;check if disk in drive ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ bsr.l read_track ;read track bsr.l decode_track ;decode track ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ addq.w #1,track-s(a5) ;next track (add/sub=increase/decrease) subq.w #1,trackct-s(a5);decrease trackcounter bne.s load_tracks ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ bsr.l Motor_off ;drivemotor off move.l bufferpt2(pc),a0;change jump in-address at bufferpt2 jsr (a0) ;jump in loaded program Exit: move.w Olddma(pc),$096(a6) move.w Oldint(pc),$09a(a6) move.w Oldadk(pc),$09e(a6) movem.l (a7)+,d0-d7/a0-a6 ;Here the normal bootroutine is following. But please notice that it's ;now impossible for the operating-system to access its disk operations ;correctly, because we used the hardware in that direct way without ;permission of the operating-system. That's the reason why you'll see ;a 'not a DOS disk'-requester after returning from the loader. So you ;see that it would be better to jump into the reset-routine instead ;of accessing the following 'find resident'-routine. ;Reset your AMIGA... ; move.l $4.w,a6 ; clr.l 38(a6) ;destroy chkbase to force... ; move.l #$fc00d2,$80.w ; trap #0 ;...cold reset ;...or be stupid and try the normal boot-procedure. move.l $4.w,a6 lea Dosname(pc),a1 jsr -96(a6) ;FindResident() move.l d0,a0 move.l 22(a0),a0 moveq #0,d0 Rts dosname:dc.b "dos.library",0 olddma: dc.w 0 oldint: dc.w 0 oldadk: dc.w 0 track: dc.w first_track trackct:dc.w 0 ;trackcounter Init_Read: clr.w $24(a6) ;DSKLEN->forbid diskdma and writing move.w #$4489,$7e(a6) ;set standard SYNC move.w #$7f00,$9e(a6) ;clear ADKCON move.w #$9500,$9e(a6) ;set required bits move.w #$0002,$9c(a6) ;clear DSKBLK bit Rts Read_Track: clr.w $24(a6) ;DSKLEN->forbid diskdma lea trackbuff(pc),a0 move.l a0,$20(a6) ;set DSKPTH and DSKPTL move.w #$9a00,$24(a6) ;enable diskdma and set amount of move.w #$9a00,$24(a6) ;words+2 to transfer. Wait_Dma: btst #1,$1f(a6) ;DSKBLK=0 ? beq.s Wait_Dma ;yeah=> wait clr.w $24(a6) ;forbid writing move.w #$0002,$9c(a6) ;clear DSKBLK Rts ;ญTimer A-delay timer: ;waits ca. 1/100 sec. move.b #$00,$bfde00 ;clear CRA move.b #$7f,$bfdd00 ;clear ICR move.b #$00,$bfd400 ;timer a -low move.b #$20,$bfd500 ;timer a -high (wait-value=$2000) move.b #$09,$bfde00 ;set oneshot/start wait_timer: btst #0,$bfdd00 ;test ta-bit/that clears ICR beq.s wait_timer rts Wait_ready: btst #5,$bfe001 ;wait for DRIVEREADY bne.s Wait_ready ;it's useless here, because the wait- Rts ;loop is long enough, but...... test_disk: btst #2,$bfe001 beq.s error Rts error: move.w $dff006,$dff180 bra.s error Select_Drive: lea floppystatus(pc),a0 lea motorstatus(pc),a1 moveq #-1,d1 ;$ffffffff -> d1 lsl.w #3,d0 ;shift selectbit to right position eor.b d0,d1 ;selectbit must be zero move.b d1,(a0) ;save byte ->floppystatus.b eori.b #$80,d1 ;clear DSKMOTOR-bit move.b d1,(a1) ;save byte ->motorstatus.b Rts Motor_On: move.b #$7f,$bfd100 ;Bits 0-6 HIGH/Bit 7 LOW nop nop move.b motorstatus(pc),d0 move.b d0,$bfd100 ;DSKMOTOR and DSKSELx LOW bsr.l Wait_Ready Rts Motor_Off: move.b #$ff,$bfd100 ;Bits 0-7 HIGH nop nop move.b motorstatus(pc),d0 ori.b #$80,d0 ;DSKMOTOR HIGH DSKSELx LOW move.b d0,$bfd100 Rts ;This routine moves the r/w-head to a track with the number stored ;in d0. A similar routine is also used by the operating-system ;(at $fea3da) Head_Pos: lea $bfd100,a0 lea s(pc),a5 tst.w d0 ;track number=0? beq.l Move_zero ;yeah=>step to track 0 move.w Tracknum(pc),d2 ;current track number cmp.w d2,d0 ;oldtrack=newtrack ? beq.s Head_end ;yes=>don't move head move.w d0,d3 move.b Floppystatus(pc),d1 bset #2,d1 ;select head 0 (lower side) btst #0,d3 ;track number even ? beq.s Down_Right ;yes=>head 0 is the right one bclr #2,d1 ;no, select head 1 (upper side) Down_Right: move.b d1,Floppystatus-s(a5) move.b d1,(a0) move.w d3,Tracknum-s(a5) ;save new track-number lsr.w #1,d2 ;d2=current cylinder lsr.w #1,d3 ;d3=new cylinder sub.w d3,d2 ;make difference bmi.s Seek_in ;diff. negativ=> step in beq.s Head_end bra.s Seek_out ;diff. positiv=> step out Seek_in: bclr #1,d1 ;step in move.b d1,Floppystatus-s(a5) neg.w d2 ;make number positive bra.s Step_Ok Seek_out: bset #1,d1 ;step out move.b d1,Floppystatus-s(a5) bra.s Step_Ok HeadStep: Step ;call step-macro Step_Ok: dbf d2,HeadStep Head_end: Rts Move_zero: ;move head to track zero move.b Floppystatus(pc),d1 bset #2,d1 bset #1,d1 move.b d1,Floppystatus-s(a5) clr.w Tracknum-s(a5) Headzero: btst #4,$bfe001 ;test if zero beq.s zero1 Step bra.s Headzero zero1: bclr #1,Floppystatus-s(a5) Step bset #1,Floppystatus-s(a5) Step bra.s Head_end ;ญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญญ ;This routine decodes the block-header and checks the format-sign. ;After this it calculates the checksum from the data-block and ;compares it with the checksum wich is stored in the block-header. ;While calculating the checksum it decodes the data block, of course. decode_track: move.l bufferpt(pc),a0 ;pointer to decodebuffer lea trackbuff(pc),a1 ;pointer to MFMbuffer moveq #11-1,d5 ;decode 11 blocks (-1 coz dbf) move.l #$55555555,d3 ;filter for tactbits decode_all_blocks: cmpi.w #$4489,(a1)+ ;1st sync-word found ? bne.s decode_all_blocks ;no=> go on searching sync_found: cmpi.w #$4489,(a1) ;2. sync-word found ? bne.s syncs_ok ;no=> all syncs skipped addq.w #2,a1 ;yes=> bra.s sync_found ;search for remaining syncs syncs_ok: ;decode infoblock move.l (a1)+,d0 ;odd bits move.l (a1)+,d1 ;even bits and.l d3,d0 and.l d3,d1 add.l d0,d0 or.l d1,d0 swap d0 andi.w #$ff00,d0 ;mask format-sign (must be $ff) cmpi.w #$ff00,d0 ;right value? bne.s formatrerror ;no==>ERROR! swap d0 andi.w #$ff00,d0 ;mask sector number*256 add.w d0,d0 ;d0=d0*2 (=sector number*512) move.l a0,a2 ;address of decodebuffer ->a2 adda.w d0,a2 ;calc. correct destination adda.w #40,a1 ;address of checksum ->a1 move.l (a1)+,d4 ;decode checksum move.l (a1)+,d1 and.l d3,d4 and.l d3,d1 add.l d4,d4 or.l d1,d4 ;store checksum ->d4 moveq #128-1,d6 ;decode 128*2 longs to 512 bytes moveq #0,d2 ;clear datachecksum decodeblock: ;decode datablock move.l 512(a1),d1 ;even bits move.l (a1)+,d0 ;odd bits eor.l d0,d2 ;calc checksum eor.l d1,d2 ;dito and.l d3,d0 ;decode longword and.l d3,d1 add.l d0,d0 or.l d1,d0 move.l d0,(a2)+ ;store longword in buffer dbf d6,decodeblock ;decode next longword and.l d3,d2 ;remove tactbits cmp.l d4,d2 ;checksum correct ? bne.s chksumerror ;no=>ERROR! adda.w #512,a1 ;reach next block dbf d5,decode_all_blocks adda.w #$1600,a0 ;bufferadr.+ 1track (5632bytes) move.l a0,bufferpt-s(a5) ;store new address Rts chksumerror: color $f00 ;backgroundcolor red st chkflag-s(a5) ;set errorflag to -1 Rts formatrerror: color $f00 ;backgroundcolor red st hdrflag-s(a5) ;set errorflag to -1 Rts tracknum: dc.w 0 floppystatus: dc.b 0 motorstatus: dc.b 0 chkflag: dc.b 0 hdrflag: dc.b 0 bufferpt: dc.l buffer bufferpt2: dc.l buffer ;here you can change the jump- ;in address of your prog. dc.b "ญ Loader by Duke of LEVEL FOUR - ASD ญ" Even trackbuff: endprg: blk.b 200,0 ;just to clear remaining bytes in mem