mirror of
https://github.com/badvision/lawless-legends.git
synced 2024-11-18 23:07:53 +00:00
343 lines
8.5 KiB
ArmAsm
343 lines
8.5 KiB
ArmAsm
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;license:BSD-3-Clause
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;minimal open/read binary file in ProDOS filesystem
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;copyright (c) Peter Ferrie 2016-2017
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!cpu 6502
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*=$800
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;zpage usage, arbitrary selection except for the "PROM constant" ones
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tmpsec = $3c
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reqsec = $3d ;PROM constant
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A1L = $3c
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A1H = $3d
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curtrk = $40 ;PROM constant
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adrlo = $44
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adrhi = $45
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sizehi = $53
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entries = $f8 ;(internal) total number of entries in directory
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step = $fd ;(internal) state for stepper motor
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tmptrk = $fe ;(internal) temporary copy of current track
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phase = $ff ;(internal) current phase for seek
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;constants
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scrn2p2 = $f87b
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dirbuf = $e00 ;for size-optimisation
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PHASEOFF = $c080
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Q6L = $c08c
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!byte 1
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lsr
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bne init
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inc reqsec
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txa
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jsr scrn2p2
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ora #$c0
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pha
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lda #$5b
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pha
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rts
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fakeMLI pla
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tax
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inx
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inx
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inx
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txa
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pha
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rts
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filename !byte filename_e - filename_b
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filename_b !text "LEGENDOS.SYSTEM" ;your start-up file, file is min 513 bytes, max 64kb
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filename_e
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init txa
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tay
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ora #$80
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sta unrseek+1
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ora #$0c
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sta unrread1+1
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sta unrread2+1
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sta unrread3+1
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sta unrread4+1
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- lda fakeMLI-1, x
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sta $beff, x
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lda #$ff
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sta $bf0f, x
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dex
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bne -
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sty $bf30
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sta $200
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opendir ;read volume directory key block
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txa
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ldx #2
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jsr readdirsel
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;include volume directory header in count
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firstent lda #<(dirbuf+4)
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sta A1L
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lda #>(dirbuf+4)
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sta A1H
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nextent ldy #0
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lda (A1L), y
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;match name lengths before attempting to match names
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lda (A1L), y
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and #$0f
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tax
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inx
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!byte $2c
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- lda (A1L), y
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cmp filename, y
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beq foundname
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;move to next directory in this block
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+ clc
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lda A1L
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adc #$27
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sta A1L
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bcc +
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;there can be only one page crossed, so we can increment instead of adc
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inc A1H
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+ cmp #<(dirbuf+$1ff) ;4+($27*$0d)
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lda A1H
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sbc #>(dirbuf+$1ff)
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bcc nextent
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;read next directory block when we reach the end of this block
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ldx dirbuf+2
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lda dirbuf+3
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jsr readdirsec
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bne firstent
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foundname iny
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dex
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bne -
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;cache EOF (file size)
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ldy #$15
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lda (A1L), y
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cmp #1
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iny
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lda (A1L), y
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adc #1
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lsr
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sta sizehi
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;cache KEY_POINTER
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ldy #$11
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lda (A1L), y
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tax
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iny
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lda (A1L), y
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;read index block in case of sapling
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jsr readdirsec
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;restore load offset
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asl adrhi
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readfile
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;fetch data block and read it
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ldy $41 ;zeroed by boot PROM
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inc $41
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ldx dirbuf, y
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lda dirbuf+256, y
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jsr seekread
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;loop while size-$200 is non-zero
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dec sizehi
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bne readfile
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readdone jmp $2000
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;no tricks here, just the regular stuff
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seek sty step
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asl phase
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txa
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asl
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copy_cur tax
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sta tmptrk
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sec
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sbc phase
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beq +++
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bcs +
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eor #$ff
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inx
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bcc ++
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+ sbc #1
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dex
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++ cmp step
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bcc +
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lda step
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+ cmp #8
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bcs +
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tay
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sec
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+ txa
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pha
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ldx step1, y
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+++ php
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bne +
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--- clc
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lda tmptrk
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ldx step2, y
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+ stx tmpsec
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and #3
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rol
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tax
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lsr
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unrseek
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lda PHASEOFF, x
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-- ldx #$13
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- dex
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bne -
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dec tmpsec
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bne --
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bcs ---
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plp
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beq seekret
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pla
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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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readadr
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- jsr readd5aa
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cmp #$96
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bne -
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ldy #3
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- sta curtrk
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jsr readnib
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rol
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sta tmpsec
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jsr readnib
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and tmpsec
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dey
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bne -
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seekret rts
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readd5aa
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-- jsr readnib
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- cmp #$d5
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bne --
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jsr readnib
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cmp #$aa
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bne -
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tay ;we need Y=#$AA later
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readnib
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unrread1
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- lda Q6L
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bpl -
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rts
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readdirsel sta adrlo
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readdirsec
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ldy #>dirbuf
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sty adrhi
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;convert block number to track/sector
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seekread lsr
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txa
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ror
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lsr
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lsr
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sta phase
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txa
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and #3
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php
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asl
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plp
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rol
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sta reqsec
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jsr readadr
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;if track does not match, then seek
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ldx curtrk
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cpx phase
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beq checksec
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jsr seek
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;force sector mismatch
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lda #$ff
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;match or read sector
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checksec jsr cmpsec
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inc reqsec
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inc reqsec
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;force sector mismatch
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cmpsecrd lda #$ff
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cmpsec cmp reqsec
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beq readdata
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jsr readadr
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beq cmpsec
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;read sector data
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readdata jsr readd5aa
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eor #$ad ;zero A if match
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;; bne * ;lock if read failure
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unrread2
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- ldx Q6L
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bpl -
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eor nibtbl - $96, x
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sta bit2tbl - $aa, y
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iny
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bne -
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unrread3
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- ldx Q6L
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bpl -
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eor nibtbl-$96, x
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sta (adrlo), y ;the real address
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iny
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bne -
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unrread4
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- ldx Q6L
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bpl -
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eor nibtbl-$96, x
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bne cmpsecrd
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-- ldx #$a9
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- inx
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beq --
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lda (adrlo), y
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lsr bit2tbl - $aa, x
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rol
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lsr bit2tbl - $aa, x
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rol
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sta (adrlo), y
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iny
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bne -
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readret inc adrhi
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rts
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bit2tbl = $300 ;PROM constant
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nibtbl = bit2tbl + 108 ;PROM constant
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dataend = nibtbl + 106 ;PROM constant
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readbuff
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!byte $D3,$C1,$CE,$A0,$C9,$CE,$C3,$AE
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