256 byte Overscan MEGATEXT Intro - (features 50Hz fullscreen scroll)
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;--------------------------------------------------------------------- ; 256 byte Overscan MegaText Intro v1.1b ; (7DX Demo Party 2011 Release) ; ; for Amstrad 464/664/6128 computers ; ; by matahari - (Dec 24, 2011) ; ; Featuring; ; - Greetings message via 50Hz hardware scroll ; - 100% overscan (full) screen size ; - Complete Amstrad palette (27 colours) on screen at once ; - And, all in 256 bytes! ;--------------------------------------------------------------------- LET ADDR_Start = &400 LET ADDR_TextMap = ADDR_Start + 256 LET CONST_TotalRasterLines = 269 LET VAR_BgrndColour = ADDR_Start - 1 LET VAR_FlipFlop = VAR_BgrndColour - 1 LET VAR_LineSkipMinus = CONST_TotalRasterLines * -9 LET VAR_LineSkipPlus = CONST_TotalRasterLines * 9 VAR_XOR equ 1 xor 0 run start org ADDR_Start start: ;--------- Generate a dummy interrupt handler --------------------------- ld hl,&c9fb ld (&0038),hl ;--------- Set CRTC Registers ------------------------------------------- ld hl,CRTC_Data loopCRTC: ld a,(hl) ld b,&bc + 1 outi ld b,&bd + 1 outi inc a jr nz,loopCRTC ;--------- Display text message ----------------------------------------- ld hl,ADDR_TextMap ld de,Message loopText: push de push hl ld a,2 call &bc0e pop hl pop de ld a,(de) cp 255 jr z,loopExec call &bb5a inc de push de ;--------- Grab pixels of displayed char -------------------------------- ld de,&c000 ld a,8 ld c,&40 outer: ex af,af' ld iy,vangelis + 1 ld (iy),%10000000 call Proc_FlipFlop inner: call Proc_FlipFlop or a jr z,bitBckgrndA ld a,&55 jr bitBckgrndB bitBckgrndA: ld a,&57 bitBckgrndB: ld (VAR_BgrndColour),a ld a,(de) vangelis: and 0 jr z,blit ld a,c ;********************************* blit: push hl push de push bc ld de,9 ld b,26 blitText: add hl,de or a jr z,blitBckgrnd ld (hl),c inc c jr blitSkip blitBckgrnd: push af ld a,(VAR_BgrndColour) ld (hl),a pop af blitSkip: djnz blitText pop bc pop de pop hl ;********************************* inc hl rr (iy) jr nc,inner inc hl ld a,8 add a,d ld d,a push bc ld bc,25*9 add hl,bc pop bc ex af,af' dec a jr nz,outer pop de jr loopText ;********************************************************************* ; MAIN LOOP - INITIALIZE! ;********************************************************************* loopExec: ld hl,ADDR_TextMap + VAR_LineSkipPlus ; Checking VBlanking only for once! ; Rest of the code will be manually synced ; via precise t-state calculations. ld b,&f5 waitVBlanking: in a,(c) rra jr nc,waitVBlanking halt di ;--------- X-Pos Alignment ---------------------------------------------- ld a,(hl) ; waste time! => 7 cycles ; Aligns perfect on WinApe. ; If you need precise ; alignment on an original Amstrad, ; you need to comment out this line ; OR replace it with a NOP! ; No worries, intro size will not ; exceed 256 bytes either way ;-) ;********************************************************************* ; MAIN LOOP - BEGIN ;********************************************************************* loopBegin: ld de,VAR_LineSkipMinus + 9 add hl,de ;--------- Wait for perfect sync! --------------------------------------- ld b,203 ; waste time! waste1: nop ; waste time! add ix,ix ; waste time! djnz waste1 ; waste time! ;--------- Start Gate Array code ---------------------------------------- ld de,CONST_TotalRasterLines ld bc,&7f00 out (c),c crash: outi inc b outi inc b outi inc b outi inc b outi inc b outi inc b outi inc b outi inc b outi inc b ld a,(hl) ; waste time! nop ; waste time! dec de ld a,d or e jr nz,crash ;--------- Raster colour = Black ---------------------------------------- ld a,&54 out (c),a nop ; waste time! ld b,(hl) ; waste time! ld b,224 ; waste time! waste2: djnz waste2 ; waste time! loopEnd: jr loopBegin ;********************************************************************* ; MAIN LOOP - END ;********************************************************************* ;--------- Procedure for Flip/Flop -------------------------------------- Proc_FlipFlop: ld a,(VAR_FlipFlop) xor VAR_XOR ld (VAR_FlipFlop),a ret ;--------- CRTC Data ---------------------------------------------------- CRTC_Data: db 1,54 ; set display width db 2,50 ; set horizontal sync db 6,34 ; set display height db 7,35 ; set vertical sync db 255 ; => EXIT LOOP Message: db ' WELCOME TO 7DX2011 ',255