diff options
Diffstat (limited to 'newtitle.s')
| -rw-r--r-- | newtitle.s | 125 |
1 files changed, 81 insertions, 44 deletions
@@ -10,16 +10,15 @@ sound_disabled = $06ff ; where our screen was loaded (see newtitle.pl) -screendata = $9000 +;screendata = $2400 ; homebrew atari xex header .word $ffff - .word version + .word origin .word end-1 - ; needs to be above the BSS (see taipan.map). we'll place it right at - ; the end of screendata. - .org $a800 +; .org $a800 + .org origin version: .incbin "ver.dat" @@ -43,21 +42,89 @@ helplotbl: .byte <(help+96) .byte 0 -helpshowing = FR1 - -; N<space> or FF (inverse) -sounddisp = help + 78 - 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: ; setup color registers @@ -162,13 +229,6 @@ keyok: sta CH rts ; return to DOS (which loads the rest of the game) -wait1jiffy: - lda RTCLOK+2 -wait: - cmp RTCLOK+2 - beq wait - rts - enable_disable_sound: lda #2 sta helpshowing @@ -187,30 +247,7 @@ now_on: sta sounddisp+1 rts - ; display list here -dlist: - .byte $70 ; 24 scanlines of blanks - .byte $70 - .byte $70 -; .byte $30 ; 4 more since image is only 184 lines tall - - .byte $0f | $40 ; LMS, BASIC mode 8 - .word screendata - .repeat 127 - .byte $0f ; 127 more scanlines of mode 8 - .endrepeat - - .byte $0f | $40 ; Hit 4K boundary, LMS again - .word screendata+$1000 - .repeat 55 - .byte $0f ; 55 more scanlines of mode 8 - .endrepeat -; .byte $30 ; blank 4 lines to match GR.8 (does it even matter?) - .byte $02 | $40 ; LMS, 1 line of GR.0 for the version -help_lms: - .word version - .byte $41 ; JVB, jump & wait for vblank - .word dlist + .out .sprintf("code ends at $%x", *) end: .word INITAD |