269 lines
3.6 KiB
ArmAsm
269 lines
3.6 KiB
ArmAsm
; the following lives on sectors $0E and $0D
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; why?
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; request sector 2 and 4, and the interleave is
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; beneath apple dos (3-23)
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; Physical (firmware) : 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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; DOS33 mapping : 0, 7, 14, 6, 13, 5, 12, 4, 11, 3, 10, 2, 9, 1, 8, 15
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; Beneath Apple DOS
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; p86 (dos reference)
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;
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.org $be00
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code_begin:
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.byte version
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readnib:
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slotpatch1: ; smc
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lda $c0d1 ; gets set to C08C (Q6L) read
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bpl readnib
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rts
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;fill address array for one track
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seekread:
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sty startsec+1
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sta tmpadr+1
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stx total+1
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inittrk:
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sec
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lda #$10
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sbc startsec+1
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cmp total+1
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bcs it_skip
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tax
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it_skip:
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stx partial1
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stx partial2
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jsr seek
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startsec:
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ldy #$d1
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tmpadr:
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tmpadr_loop:
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lda #$d1
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sta addrtbl, y
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inc tmpadr+1
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iny
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dec partial1
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bne tmpadr_loop
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read:
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outer_read:
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jsr readnib
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inner_read:
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cmp #$d5
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bne outer_read
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jsr readnib
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cmp #$aa
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bne inner_read
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tay ; we need Y=#$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 #$96 is assumed
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ldy #2 ; volume, track, sector
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another:
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jsr readnib
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rol ; set carry
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sta sector+1
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jsr readnib
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and sector+1
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dey
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bpl another
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tay
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ldx addrtbl, Y ; fetch corresponding address
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beq read
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sta sector+1 ; store index for later
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stx adrpatch1+2
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stx adrpatch8+2
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stx adrpatch2+2
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stx adrpatch3+2
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stx adrpatch5+2
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stx adrpatch7+2
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inx
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stx adrpatch9+2
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dex
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dex
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stx adrpatch4+2
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stx adrpatch6+2
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ldy #$fe
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adrpatch1:
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loop2:
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lda $d102, Y
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pha
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iny
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bne loop2
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branch_read:
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bcs read ; branch always
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check_mode:
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cpx #0
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beq read ; loop if not expecting #$AD
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loop33:
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sta tmpval+1 ; zero rolling checksum
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slotpatch2:
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loop4:
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ldx $c0d1
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bpl loop4
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lda preshift-$96, X
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adrpatch2:
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sta $d102, Y ; store 2-bit array
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tmpval:
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eor #$d1
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iny
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bne loop33
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ldy #$aa
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slotpatch3:
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loop5:
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ldx $c0d1
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bpl loop5
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eor preshift-$96, X
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adrpatch3:
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ldx $d102, Y ; bit2tbl
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eor grouped+2, X ; first 86 nibbles use group bits 0-1
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adrpatch4:
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sta $d156, y
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iny
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bne loop5
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and #$fc
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ldy #$aa
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slotpatch4:
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loop6:
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ldx $c0d1
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bpl loop6
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eor preshift-$96, X
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adrpatch5:
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ldx $d102, Y ; bit2tbl
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eor grouped+1, X ; second 86 nibbles use group bits 2-3
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adrpatch6:
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sta $d1ac, Y
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iny
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bne loop6
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and #$fc
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ldx #$ac
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slotpatch5:
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loop7:
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ldy $c0d1
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bpl loop7
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eor preshift-$96, Y
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adrpatch7:
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ldy $d100, X ; bit2tbl
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eor grouped, Y ; last 84 nibbles use group bits 4-5
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adrpatch8:
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sta $d100, x
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inx
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bne loop7
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and #$fc
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slotpatch6:
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loop8:
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ldy $c0d1
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bpl loop8
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eor preshift-$96, Y
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cmp #1 ; carry = !zero
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ldy #1
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loop9:
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pla
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adrpatch9:
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sta $d100, Y
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dey
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bpl loop9
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branch_read2:
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bcs branch_read ; branch if checksum failure
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sector:
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ldy #$d1
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txa
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sta addrtbl, Y ; zero corresponding address
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dec total+1
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dec partial2 ; adjust remaining count (faster than looping over array)
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sec
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bne branch_read2 ; read all requested sectors in one track
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total:
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ldx #$d1
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beq driveoff
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inc phase+1
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inc phase+1 ; update current track
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jmp inittrk
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driveoff:
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slotpatch7:
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lda $c0d1
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seekret:
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rts
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seek:
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lda #0
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sta step+1
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copy_cur:
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curtrk:
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lda #0
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sta tmpval+1
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sec
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phase:
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sbc #$d1
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beq seekret
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eor #$ff
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inc curtrk+1
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cmp step+1
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bcc loop10
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step:
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lda #$d1
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loop10:
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cmp #8
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bcs loop11
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tay
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sec
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loop11:
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lda curtrk+1
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ldx step1, Y
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bne loop12
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loopmmm:
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clc
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lda tmpval+1
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ldx step2, Y
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loop12:
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stx sector+1
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and #3
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rol
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tax
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slotpatch8:
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sta $c0d1, X
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loopmm:
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ldx #$13
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loopm:
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dex
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bne loopm
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dec sector+1
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bne loopmm
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lsr
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bcs loopmmm
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inc step+1
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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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addrtbl: .res 16
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partial1 = *
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partial2 = partial1+1
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code_end=partial2+1
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