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|
; this file needs to be assembled with:
; cl65 -o newtitle.xex -t none newtitle.s
; It contains only an init routine, no run address.
.include "atari.inc"
; location sound code will look at to see whether sound
; is disabled (0 = enabled, !0 = disabled). If you
; change this here, change it in sounds.h also!
sound_disabled = $06ff
; since we're changing the font and colors, we'll save the old
; ones here. If you change these, change them in taipan.c
; also.
fontsave = $06fc
color1save = $06fd
color2save = $06fe
; where our screen was loaded (see newtitle.pl)
;screendata = $2400
; homebrew atari xex header
.word $ffff
.word origin
.word end-1
; .org $a800
.org origin
version:
.incbin "ver.dat"
help:
.incbin "help.dat"
helphitbl:
.byte >version
.byte >help
.byte >(help+32)
.byte >(help+64)
.byte >(help+96)
.byte 0
helplotbl:
.byte <version
.byte <help
.byte <(help+32)
.byte <(help+64)
.byte <(help+96)
.byte 0
colorchoices:
.byte $c0,$10,$00
colorcount = (*-colorchoices)-1
textchoices:
.byte $0c,$0e,$0a
textcount = (*-textchoices)-1
wait1jiffy:
lda RTCLOK+2
wait:
cmp RTCLOK+2
beq wait
rts
; this is needed to prevent the DL from crossing a 1K boundary.
filler:
.repeat 3
.byte $aa
.endrepeat
; since the screen data crosses a 4K boundary, we have to
; include a LMS. screendata needs to be on a 32-byte boundary for
; these calculations to work.
.if(screendata .mod $20)
.error "screendata must be on a 32-byte boundary!"
.endif
totalscanlines = 184 ; aka image size / $20
topscanlines = (($1000 - (screendata .mod $1000)) / $20)
bottomscanlines = totalscanlines - topscanlines
.out .sprintf("topscanlines = %d", topscanlines)
.out .sprintf("bottomscanlines = %d", bottomscanlines)
; if the display list crosses a 1K boundary, it needs to contain a
; jmp instruction ($01).
.macro dlbyte arg
.if((* .mod $400) = $3fd)
.out .sprintf("emitting DL jump to $%x at $%x", * + 3, *)
.byte $01
.word (* + 2)
.endif
.byte arg
.endmacro
.macro dl3byte ins, arg
.local bytes
bytes = $400 - (* .mod $400)
.if(bytes < 3)
.error .sprintf("$%x %d: display list dl3byte when <3 bytes left in 1K block, sorry", *, bytes)
.endif
.byte ins
.word arg
.endmacro
; display list here
dlist:
dlbyte $70 ; 24 scanlines of blanks
dlbyte $70
dlbyte $70
dl3byte $0f | $40, screendata ; LMS, BASIC mode 8
.repeat topscanlines - 1
dlbyte $0f ; 127 more scanlines of mode 8
.endrepeat
dl3byte $0f | $40, screendata+(topscanlines * $20) ; Hit 4K boundary, LMS again
.repeat bottomscanlines
dlbyte $0f ; 55 more scanlines of mode 8
.endrepeat
dl3byte $02 | $40, version ; LMS, 1 line of GR.0 for the version
help_lms = * - 2
dl3byte $41, dlist ; JVB, jump & wait for vblank
.out .sprintf("dl start $%x, end $%x, size %d", dlist, *, (* - dlist) + 1)
.out .sprintf("C code can load at $%x", * + 1)
helpshowing = FR1
; here is where we store N<space> or FF (inverse)
sounddisp = help + 78
; executable code here
start:
; save old color registers and font addr.
lda CHBAS
sta fontsave
lda COLOR1
sta color1save
lda COLOR2
sta color2save
; setup color registers
lda colorchoices
sta COLOR2 ; text bg
lda textchoices
sta COLOR1 ; text fg
; turn off screen, in case vblank happens while we work
lda #0
sta FR0
sta SDMCTL
; build our display list
; TODO, for now it's hardcoded (see 'dlist' below)
; wait for the next frame, to avoid graphics glitching
jsr wait1jiffy
; setup our display list
lda SDLSTL
sta FR0
lda SDLSTH
sta FR0+1
lda #<dlist
sta SDLSTL
lda #>dlist
sta SDLSTH
; switch to narrow playfield, enable screen
lda #$21
sta SDMCTL
; clear any keypress that happened during loading
lda #$ff
sta CH
ldx #0 ; X = index into bg color choices
ldy #0 ; Y = index into text color choices
; wait for user to press a key
wait4key:
lda colorchoices,x
sta COLOR2
lda textchoices,y
sta COLOR1
lda CH
cmp #$ff
beq wait4key
cmp #28 ; Escape key
bne not_esc
; show next line of help
showhelp:
stx FR1+1
ldx helpshowing
inx
loadhelp:
lda helphitbl,x
bne helpok
ldx #0
beq loadhelp
helpok:
sta help_lms+1
lda helplotbl,x
sta help_lms
stx helpshowing
ldx FR1+1
clc
bcc x_ok
not_esc:
cmp #62 ; S key
bne not_s
jsr enable_disable_sound
clc
bcc showhelp
not_s:
cmp #21 ; B key
bne not_b
dex
bpl x_ok
ldx #colorcount
bne x_ok
not_b:
cmp #45 ; T key
bne keyok
dey
bpl x_ok
ldy #textcount
x_ok:
lda #$ff
sta CH
bne wait4key
keyok:
; eat the keypress
lda #$ff
sta CH
rts ; return to DOS (which loads the rest of the game)
enable_disable_sound:
lda #2
sta helpshowing
lda sound_disabled
eor #$01
sta sound_disabled
beq now_on
lda #166 ; inverse F screen code
sta sounddisp
sta sounddisp+1
rts
now_on:
lda #174 ; inverse N screen code
sta sounddisp
lda #128 ; inverse space screen code
sta sounddisp+1
rts
.out .sprintf("code ends at $%x", *)
end:
.word INITAD
.word INITAD+1
.word start
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