167 lines
6.0 KiB
ArmAsm
167 lines
6.0 KiB
ArmAsm
;fast boot-loader in one sector
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;"special delivery" version for Directi-DOS
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;copyright (c) Peter Ferrie 2016
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;thanks to 4am for inspiration and testing
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;assemble using ACME
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;
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;Cleanup by Michael Pohoreski "Michaelangel007"
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;https://github.com/Michaelangel007/Directi-DOS
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!cpu 6502
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!to "fstbt",plain
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; Disk
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PHASEOFF = $c080
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PHASEON = $c081
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; P6PROM
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P6BUFF = $26 ; ZP: 16-bit pointer to decoded disk nibbles
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P6SLOTx16 = $2b ; ZP: Slot * 16, #$C600 -> #$60
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P6SECTOR = $3D ; ZP: Sector to read
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P6TRKHAVE = $40 ; ZP: Track Found or Actual
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P6TRKWANT = $41 ; ZP: Track Wanted or Expected
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P6READSEC = $c05c ; + P6SLOTx16 = $C65c: CLC, PHP, read sector
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; Text Screen Holes
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; Apple II Monitors Peeled, Page 16, Peripheral Controller Work Areas
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; Laser 128 Reference Manual, Page 52, Figure 5.2, 4o Column Text Mode
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;
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; |Row |Slot 0|Slot 1|Slot 2|Slot 3|Slot 4|Slot 5|Slot 6|Slot 7|
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; |:--:|:-----|:-----|:-----|:-----|:-----|:-----|:-----|:-----|
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; | 0 | $478 | $479 | $47A | $47B | $47C | $47D | $47E | $47F |
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; | 1 | $4F8 | $4F9 | $4FA | $4FB | $4FC | $4FD | $4FE | $4FF |
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; | 2 | $578 | $579 | $57A | $57B | $57C | $57D | $57E | $57F |
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; | 3 | $5F8 | $5F9 | $5FA | $5FB | $5FC | $5FD | $5FE | $5FF |
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; | 4 | $678 | $679 | $67A | $67B | $67C | $67D | $67E | $67F |
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; | 5 | $6F8 | $6F9 | $6FA | $6FB | $6FC | $6FD | $6FE | $6FF |
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; | 6 | $778 | $779 | $77A | $77B | $77C | $77D | $77E | $77F |
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; | 7 | $7F8 | $7F9 | $7FA | $7FB | $7FC | $7FD | $7FE | $7FF |
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TXTHOLE00 = $478
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TXTHOLE31 = $4fb
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; Graphics!
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SCRN2 = $f879
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; Mem/Softswitches
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ROMIN = $c081 ; Disable LC Bank, read ROM
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LCBANK2 = $c083
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CLR80VID = $c00c ; OFF 80-column display mode
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CLRALTCH = $c00e ; OFF alternate character set (MouseText)
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; Misc
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INIT = $fb2f ; Set Text Mode, Set Window
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WAIT = $fca8 ; wait _minimum_ 1/2(26+27 A+5A'^2) cycles -> *14 / 14.318181 uSeconds; see: Technote #12: The Apple II Firmware WAIT Routine
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SETKBD = $fe89 ; IN#0
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SETVID = $fe93 ; PR#0
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; .org $0800 ; 16-sector P6PROM Reads T0S0 into $0800
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*=$800
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!byte 1 ; First Byte = Number of sectors to read
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tay ;A is last read sector+1 on entry
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lda ROMIN ;bank in ROM
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;check array before checking sector number
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;allows us to avoid a redundant seek if all slots are full in a track,
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;and then the list ends
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incindex
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inc adrindex + 1 ;select next address
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adrindex
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lda adrtable - 1 ;15 entries in first row, 16 entries thereafter
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sta TXTHOLE31 ;set 80-column state (final store is an #$FF to disable it)
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cmp #$FF
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beq jmpoep ;#$FF means end of data
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sta P6BUFF+1 ;set high part of address
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;2, 4, 6, 8, $0A, $0C, $0E
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;because PROM increments by one itself
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;and is too slow to read sectors in purely incremental order
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;so we offer every other sector for read candidates
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iny
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cpy #$10 ; 16 sectors/track
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bcc setsector ;cases 1-$0F
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beq sector1 ;finished with $0E
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;next should be 1 for 1, 3, 5, 7... sequence
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;finished with $0F, now we are $11, so 16 sectors done
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jsr seek ;returns A=0
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;back to 0
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tay
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!byte $2C ; BIT $xxyy: mask LDY #1
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sector1
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ldy #1
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setsector
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sty P6SECTOR ;set sector
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iny ;prepare to be next sector in case of unallocated sector
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lda P6BUFF+1
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beq incindex ;empty slot, back to the top
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;convert slot to PROM address
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; F879 SCRN2 BCC RTMASKZ
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; F87B LSR
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; F87C LSR
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; F87D LSR
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; F87E LSR
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; F87F RTMASKZ AND #$0F
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; F881 RTS
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txa
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jsr SCRN2+2 ;4xlsr
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tay
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ora #>P6READSEC ; Hi: $C0 -> $C65C = P6ReadSector
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pha
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lda #<P6READSEC-1 ; Lo: $5B -> P6ReadSector-1
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pha
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lda #2
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sta TXTHOLE00, y ;save current phase for DOS use when we exit
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writeenable
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lda LCBANK2
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lda LCBANK2 ;write-enable RAM and bank it in so read can decode
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rts ;return to PROM
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seek
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inc P6TRKWANT ;next track
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asl P6TRKHAVE ;carry clear, phase off
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jsr seek1 ;returns carry set, not useful
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clc ;carry clear, phase off
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seek1
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jsr delay ;returns with carry set, phase on
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inc P6TRKHAVE ;next phase
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delay
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lda P6TRKHAVE
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and #3
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rol
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ora P6SLOTx16 ;merge in slot
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tay
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lda PHASEOFF, y
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lda #$30
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jmp WAIT ;common delay for all phases
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jmpoep
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jsr SETKBD ;rehook keyboard (needed particularly after PR#)
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jsr SETVID ;rehook video
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jsr INIT ;text mode
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sta CLR80VID
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sta CLRALTCH ;clear 80-column mode
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jsr writeenable ;bank in our RAM, write-enabled
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jmp $D000 ;jump to unpacker
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adrtable
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!byte $dd,$dc,$db,$da,$d9,$d8,$d7 ;T0S# 2,4,6,8,A,C,E
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!byte $d6,$d5,$d4,$d3,$d2,$d1,$d0,$de ; 1,3,5,7,9,B,D,F
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!byte $df,$ed,$ec,$eb,$ea,$e9,$e8,$e7 ;T1S# 0,2,4,6,8,A,C,E
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!byte $e6,$e5,$e4,$e3,$e2,$e1,$e0,$ee ; 1,3,5,7,9,B,D,F
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!byte $FF ;end of list
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