mirror of
https://github.com/deater/dos33fsprogs.git
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214 lines
4.2 KiB
ArmAsm
214 lines
4.2 KiB
ArmAsm
;fast bootable seek/read, slot 6 version
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;copyright (c) Peter Ferrie 2011-2012
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; Translated to ca64 by Vince Weaver
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chksum = 0 ;otherwise safer but 12 bytes larger
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secldr2 = $0e ;14th sector is fastest when loaded from bootsector but can be any of them
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seekback = 0 ;set to 1 to enable seek backwards
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adrlo = $26 ;constant from boot prom
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adrhi = $27 ;constant from boot prom
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slot = $2b ;constant from boot prom
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tmpsec = $3c ;constant from boot prom
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tmpadr = $41
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partial2 = $f9 ;copy of partial1
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partial1 = $fa ;sectors to read from one track
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total = $fb ;total sectors to read
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step = $fc ;state for stepper motor
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tmptrk = $fd ;temporary copy of current track
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curtrk = $fe ;current track (must initialise before calling seek)
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phase = $ff ;current phase for seek
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addrtbl = $50 ;requires 16 bytes
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nibtbl = $2d6 ;constant from boot prom
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bit2tbl = $200 ;hard-coded (uses $2aa-$2ff)
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maxsec = $10 ;sectors per track, usually 10 but 0b for Olympic Decathlon, 0c for Karateka
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;this section is specific to bootsectors
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;load second stage sector to $900, enabling track seek
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tax ;1 sector
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lda #secldr2
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ldy #9
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jsr seekread
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jmp ldr2
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;
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seekread: stx total
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sta addrtbl
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sty tmpadr
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calcpart: sec
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lda #maxsec
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sbc addrtbl
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cmp total
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bcs L1
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tax
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L1: stx partial1
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stx partial2
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callseek: jsr seek - 1 ;(seekret) disabled during boot, increment to enable
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ldy addrtbl
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ldx #$0f
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lda #0
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L2: sta addrtbl, x
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dex
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bpl L2
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L3: lda tmpadr
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ldx sectbl, y
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sta addrtbl, x
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inc tmpadr
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iny
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dec partial1
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bne L3
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read: ldx #0
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read1:
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L4: jsr readnib
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L5: cmp #$d5
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bne L4
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jsr readnib
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cmp #$aa
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bne L5
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tay ;we need Y=#$AA later
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jsr readnib
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eor #$ad ;zero A if match
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beq check_mode
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;if not #$AD, then #$96 is assumed
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ldy #2 ;high 8 bits of bit2tbl
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sty adrhi ;store 2-bits array at $2xx
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L6: jsr readnib
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rol ;set carry
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sta tmpsec
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jsr readnib
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and tmpsec
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dey
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bpl L6
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.if chksum
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sta tmpsec
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tay
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ldx addrtbl, y
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stx step
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.else
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tay
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lda addrtbl, y
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sta step
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stx addrtbl, y
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tax
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.endif
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bcs read1
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check_mode: cpx #0 ;set carry if non-zero
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beq read1
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.byte $90
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L7: clc
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L8: ldx $c0ec
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bpl L8
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eor nibtbl, x
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sta (adrlo), y ;$2xx initially, and then the real address
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iny
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bne L8
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ldx step
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stx adrhi ;set real address
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bcs L7 ;carry is set on first pass, clear on second, loops one time
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.if chksum
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L9: ldx $c0ec
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bpl L9
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eor nibtbl, x
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bne read
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ldx tmpsec
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sta addrtbl, x
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.endif
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L10: ldx #$a9
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L11: inx
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beq L10
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lda (adrlo), y
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lsr bit2tbl, x
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rol
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lsr bit2tbl, x
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rol
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sta (adrlo), y
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iny
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bne L11
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dec total
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dec partial2
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bne read ;read all requested sectors in one track
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ldx total
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beq seekret
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inc phase
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inc phase ;update current track
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jmp calcpart
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sectbl: .byte 0, $0d, $0b, 9, 7, 5, 3, 1, $0e, $0c, $0a, 8, 6, 4, 2, $0f
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readnib:
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L12: lda $c0ec
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bpl L12
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seekret: rts ;hard-coded relative to seek
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seek: lda #0
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sta step
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copy_cur: lda curtrk
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sta tmptrk
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sec
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sbc phase
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beq seekret
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.if seekback
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bcs L13
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.endif
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eor #$ff
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inc curtrk
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.if seekback
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bcc L14
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L13: adc #$fe
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dec curtrk
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L14:
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.endif
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cmp step
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bcc L15
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lda step
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L15: cmp #8
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bcs L16
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tay
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sec
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L16: lda curtrk
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ldx step1, y
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bne L18
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L17: clc
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lda tmptrk
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ldx step2, y
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L18: stx tmpsec
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and #3
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rol
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tax
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sta $c0e0, x
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L19: ldx #$13
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L20: dex
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bne L20
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dec tmpsec
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bne L19
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lsr
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bcs L17
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inc step
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bne copy_cur
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step1: .byte 1, $30, $28, $24, $20, $1e, $1d, $1c
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step2: .byte $70, $2c, $26, $22, $1f, $1e, $1d, $1c
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newtrk = $42 ;track*2 for main stage
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newnum = $1f ;number of sectors in main stage
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newsec = 1 ;first sector in main stage
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newadr = $61 ;load address for main stage
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newstart = $6100 ;start address for main stage
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ldr2: jmp ldr2
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;replace with something like the following:
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;inc callseek + 1
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;sty curtrk
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;lda #newtrk
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;sta phase
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;ldx #newnum
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;lda #newsec
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;ldy #newadr
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;jsr seekread
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;jmp newstart
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