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dos33fsprogs/demos/another_myst/loader.s
Vince Weaver b1238af49d re-arranged the entire directory structure 
this will probably upset people
2021-01-05 15:29:31 -05:00

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; Loader for OOTW
; Used to be standalone, now loaded as part of TITLE
; But still loads at $1400
; the TITLE program sets $05 with which thing to load
; this part of the program stays resident, so when a level ends
; it changes $05 (WHICH_LOAD) and this code loads the proper executable
nibtbl = $300 ; nothing uses the bottom 128 bytes of $300, do they?
bit2tbl = $380 ; bit2tbl: .res 86 ; = nibtbl+128
filbuf = $3D6 ; filbuf: .res 4 ; = bit2tbl+86
; read any file slot 6 version
; based on FASTLD6 and RTS copyright (c) Peter Ferrie 2011-2013,2018
; modified to assembled with ca65 -- vmw
; added code to patch it to run from current disk slot -- vmw
; WHICH_LOAD = $05 ; thing to load
adrlo = $26 ; constant from boot prom
adrhi = $27 ; constant from boot prom
tmpsec = $3c ; constant from boot prom
reqsec = $3d ; constant from boot prom
sizelo = $44
sizehi = $45
secsize = $46
namlo = $f8
namhi = $f9
; TEMPY = $fa
step = $fd ; state for stepper motor
tmptrk = $fe ; temporary copy of current track
phase = $ff ; current phase for /seek
; OUTL = $fe ; for picking filename
; OUTH = $ff
dirbuf = $c00
; note, don't put this immediately below
; the value being read as destaddr-4
; is temporarily overwritten during read
; process
FILENAME = $280
;===================================================
;===================================================
; START / INIT
;===================================================
;===================================================
loader_start:
jsr init ; unhook DOS, init nibble table
;===================================================
;===================================================
; SETUP THE FILENAME
;===================================================
;===================================================
which_load_loop:
ldx WHICH_LOAD
beq load_intro
jmp load_ending
lda #<ootw_filename
sta OUTL
lda #>ootw_filename
sta OUTH
ldy #6
cpx #10
bcc load_less_than_10 ; blt
txa
sec
sbc #10
tax
lda #'1' ; assume it's 10-15
sta (OUTL),Y
iny
load_less_than_10:
txa
clc
adc #48
sta (OUTL),Y
iny
lda #0
sta (OUTL),Y ; be sure NUL terminated
; might be issue if load >10 level
; then back to lower? that possible?
jmp opendir_filename
load_intro:
lda #<intro_filename
sta OUTL
lda #>intro_filename
sta OUTH
bne opendir_filename ; branch always
load_ending:
lda #<ending_filename
sta OUTL
lda #>ending_filename
sta OUTH
; fallthrough
;===================================================
;===================================================
; SET UP DOS3.3 FILENAME
;===================================================
;===================================================
opendir_filename:
; clear out the filename with $A0 (space)
lda #<FILENAME
sta namlo
lda #>FILENAME
sta namhi
ldy #29
wipe_filename_loop:
lda #$A0
sta (namlo),Y
dey
bpl wipe_filename_loop
ldy #0
copy_filename_loop:
lda (OUTL),Y
beq copy_filename_done
ora #$80
sta (namlo),Y
iny
bne copy_filename_loop
copy_filename_done:
jsr opendir ; open and read entire file into memory
jsr $1700 ; jump to common entry point
; hope they updated the WHICH_LOAD value
jmp which_load_loop
; filename to open is 30-character Apple text, must be padded with space ($A0)
;filename:
; .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0
; .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0
; .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0
intro_filename:
.byte "INTRO",0
ending_filename:
.byte "ANOTHERMIST",0
ootw_filename:
.byte "OOTW_C",0,0,0
;===================================================
;===================================================
; INIT (build nibble table)
;===================================================
;===================================================
;unhook DOS and build nibble table
init:
; patch to use current drive
; locate input paramater list
jsr $3E3
; result is in A:Y
sta $FF
sty $FE
ldy #1
lda ($FE),y
; list+1 should have slot<<8
ora #$80 ; add in $80
; c0e0
sta mlsmc06+1
; c0e8
clc
adc #8
sta mlsmc02+1
sta mlsmc07+1
; c0e9
clc
adc #1
sta mlsmc01+1
; c0ec
clc
adc #3
sta mlsmc03+1
sta mlsmc04+1
sta mlsmc05+1
jsr $fe93 ; clear COUT
jsr $fe89 ; clear KEYIN
;========================
; Create nibble table
; Note: the table starts 16 bytes in, and is sparse
; so it doesn't entirely look like the DOS33 table at
ldy #0
ldx #3
L1: stx $3c ; store tempx (3?)
txa ; a=x (a=3)
asl ; a*=2 (a=6)
bit $3c ; a&tempx, set N/V (a=6)
beq L3 ; if 0, skip to L3
ora $3c ; a|=tempx (a=7)
eor #$ff ; a=~a (a=f8)
and #$7e ; a&=0x7e 0111 1110 (a=78)
L2: bcs L3 ; this set way back at asl??
lsr ; a>>1 a=3c c=0
; a=1e c=0
; a=0f c=0
; a=07 c=1
bne L2 ; if a!=0 goto l2
tya ; if a==0, a=y
sta nibtbl, x ; write out to table
iny ; increment y
L3: inx ; increment x x=4, a=0f
bpl L1 ; loop while high bit not set
rts
;===================================================
;===================================================
; file not found
;===================================================
;===================================================
file_not_found:
mlsmc07:lda $c0e8 ; turn off drive motor?
jsr TEXT
jsr HOME
ldy #0
lda #<disk_string
sta OUTL
lda #>disk_string
sta OUTH
quick_print:
lda (OUTL),Y
beq quick_print_done
jsr COUT1
iny
jmp quick_print
quick_print_done:
; rts
; jsr quick_print
fnf_keypress:
lda KEYPRESS
bpl fnf_keypress
bit KEYRESET
jmp which_load_loop
disk_string:
.byte "INSERT OTHER DISK, PRESS RETURN",0
;===================================================
;===================================================
; OPENDIR: actually load the file
;===================================================
;===================================================
; turn on drive and read volume table of contents
opendir:
mlsmc01:lda $c0e9 ; turn slot#6 drive on
ldx #0
stx adrlo ; zero out adrlo
stx secsize ; zero out secsize
lda #$11 ; a=$11 (VTOC)
jsr readdirsec
firstent:
lda dirbuf+1
; lock if entry not found
entry_not_found:
beq file_not_found
; read directory sector
ldx dirbuf+2
jsr seekread1
ldy #7 ;number of directory entries in a sector
ldx #$2b ;offset of filename in directory entry
nextent:
tya
pha ; was **phy**
txa
pha ; was **phx**
ldy #$1d
; match name backwards (slower but smaller)
L4:
lda (namlo), y
cmp dirbuf, x
beq foundname
pla
; move to next directory in this block, if possible
clc
adc #$23
tax
pla
tay ; was **ply**
dey
bne nextent
beq firstent ; was **bra**
foundname:
dex
dey
bpl L4
pla
tay ; was **ply**
pla
; read track/sector list
lda dirbuf-32, y
ldx dirbuf-31, y
jsr seekread1
; read load offset and length info only, initially
lda #<filbuf
sta adrlo
lda #4
sta secsize
lda dirbuf+12
ldx dirbuf+13
ldy #>filbuf
jsr seekread
; reduce load offset by 4, to account for offset and length
sec
lda filbuf
sbc #4
sta adrlo
lda filbuf+1
sbc #0
sta adrhi
; save on stack bytes that will be overwritten by extra read
ldy #3
L5:
lda (adrlo), y
pha
dey
bpl L5
lda adrhi
pha
lda adrlo
pha
; increase load size by 4, to account for offst and length
lda filbuf+2
adc #3
sta sizelo
sta secsize
lda filbuf+3
adc #0
sta sizehi
beq readfirst
lda #0 ; was **stz secsize**
sta secsize
readfirst:
ldy #$0c
; read a file sector
readnext:
tya
pha
lda dirbuf, y ; A = track
ldx dirbuf+1, y ; x = sector
jsr seekread1
pla
tay
; if low count is non-zero then we are done
; (can happen only for partial last block)
lda secsize
bne readdone
; continue if more than $100 bytes left
dec sizehi
bne L6
; set read size to min(length, $100)
lda sizelo
beq readdone
sta secsize
L6:
inc adrhi
iny
iny
bne readnext
; save current address for after t/s read
lda adrhi
pha
lda adrlo
pha
lda #0
sta adrlo ; was **stz adrlo**
; read next track/sector sector
lda dirbuf+1
ldx dirbuf+2
jsr readdirsec
clc
; restore current address
readdone:
pla
sta adrlo ; code originally had this backwards
pla
sta adrhi
bcc readfirst
mlsmc02:lda $c0e8
; restore from stack bytes that were overwritten by extra read
ldx #3
ldy #0
L7:
pla
sta (adrlo), y
iny
dex
bpl L7
rts
;======================
; readdirsec
;======================
; a = track?
; x = sector?
readdirsec:
ldy #>dirbuf
seekread:
sty adrhi
seekread1:
sta phase
lda sectbl, x
sta reqsec
jsr readadr
; if track does not match, then seek
cpx phase
beq checksec
jsr seek
;=========================================
; re merge in with qkumba's recent changes
; to fix seek problem?
;=========================================
; [re-]read sector
re_read_addr:
jsr readadr
checksec:
cmp reqsec
bne re_read_addr
;=========================
; read sector data
;=========================
readdata:
jsr readd5aa
eor #$ad ; zero A if match
bne re_read_addr
L12:
mlsmc03:ldx $c0ec ; read until valid data (high bit set)
bpl L12
eor nibtbl-$80, x
sta bit2tbl-$aa, y
iny
bne L12
L13:
mlsmc04:ldx $c0ec ; read until valid data (high bit set)
bpl L13
eor nibtbl-$80, x
sta (adrlo), y ; the real address
iny
cpy secsize
bne L13
ldy #0
L14:
ldx #$a9
L15:
inx
beq L14
lda (adrlo), y
lsr bit2tbl-$aa, x
rol
lsr bit2tbl-$aa, x
rol
sta (adrlo), y
iny
cpy secsize
bne L15
rts
; no tricks here, just the regular stuff
;=======================
; readaddr -- read the address field
;=======================
; Find address field, put track in cutrk, sector in tmpsec
readadr:
jsr readd5aa
cmp #$96
bne readadr
ldy #3 ; three?
; first read volume/volume
; then track/track
; then sector/sector?
adr_read_two_bytes:
tax
jsr readnib
rol
sta tmpsec
jsr readnib
and tmpsec
dey
bne adr_read_two_bytes
rts
;========================
; make sure we see the $D5 $AA pattern
readd5aa:
L16:
jsr readnib
L17:
cmp #$d5
bne L16
jsr readnib
cmp #$aa
bne L17
tay ; we need Y=#$AA later
readnib:
mlsmc05:lda $c0ec ; read until valid (high bit set)
bpl readnib
seekret:
rts
;=====================
; SEEK
;=====================
; current track in X?
; desired track in phase
seek:
ldy #0
sty step
asl phase ; multiply by two
txa ; current track?
asl ; mul by two
copy_cur:
tax
sta tmptrk
sec
sbc phase
beq L22
bcs L18
eor #$ff
inx
bcc L19
L18:
sbc #1
dex
L19:
cmp step
bcc L20
lda step
L20:
cmp #8
bcs L21
tay
sec
L21:
txa
pha
ldx step1, y
L22:
php
bne L24
L23:
clc
lda tmptrk
ldx step2, y
L24:
stx tmpsec
and #3
rol
tax
lsr
mlsmc06:lda $c0e0, x
L25:
ldx #$12
L26:
dex
bpl L26
dec tmpsec
bne L25
bcs L23
plp
beq seekret
pla
inc step
bne copy_cur
step1: .byte $01, $30, $28, $24, $20, $1e, $1d, $1c
step2: .byte $70, $2c, $26, $22, $1f, $1e, $1d, $1c
sectbl: .byte $00,$0d,$0b,$09,$07,$05,$03,$01,$0e,$0c,$0a,$08,$06,$04,$02,$0f
; From $BA96 of DOS33
;nibtbl: .res 128 ; = *
; .byte $00,$01,$98,$99,$02,$03,$9C,$04 ; $BA96 ; 00
; .byte $05,$06,$A0,$A1,$A2,$A4,$A4,$A5 ; $BA9E ; 08
; .byte $07,$08,$A8,$A9,$AA,$09,$0A,$0B ; $BAA6 ; 10
; .byte $0C,$0D,$B0,$B1,$0E,$0F,$10,$11 ; $BAAE ; 18
; .byte $12,$13,$B8,$14,$15,$16,$17,$18 ; $BAB6 ; 20
; .byte $19,$1A,$C0,$C1,$C2,$C3,$C4,$C5 ; $BABE ; 28
; .byte $C6,$C7,$C8,$C9,$CA,$1B,$CC,$1C ; $BAC6 ; 30
; .byte $1D,$1E,$D0,$D1,$D2,$1E,$D4,$D5 ; $BACE ; 38
; .byte $20,$21,$D8,$22,$23,$24,$25,$26 ; $BAD6 ; 40
; .byte $27,$28,$E0,$E1,$E2,$E3,$E4,$29 ; $BADE ; 48
; .byte $2A,$2B,$E8,$2C,$2D,$2E,$2F,$30 ; $BAE6 ; 50
; .byte $31,$32,$F0,$F1,$33,$34,$35,$36 ; $BAEE ; 58
; .byte $37,$38,$F8,$39,$3A,$3B,$3C,$3D ; $BAF6 ; 60
; .byte $3E,$3F,$13,$00,$01,$02,$01,$00 ; $BAFE ; 68
; .byte $00,$00,$00,$00,$00,$00,$00,$00
; .byte $00,$00,$00,$00,$00,$00,$00,$00
;bit2tbl: .res 86 ; = nibtbl+128
;filbuf: .res 4 ; = bit2tbl+86
;dataend = filbuf+4
loader_end:
.assert (<loader_end - <loader_start)>3, error, "loader too big"
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