Subject: [stella] Useless Information Department|
From: Christopher Tumber <christophertumber@xxxxxxxxxx>
Date: Thu, 19 Dec 2002 11:35:18 -0500
FWIW, you can use the sprite replication trick (sta RESP0/sta RESP1/sta RESP0) with the Missiles. Why you would ever want to do this when the bitmaps available through the Player objects is much more usefull, I don't know (perhaps to preserve the Player's vertical positioning if you only need a very simple pattern?) At any rate, maybe somebody, someday finds a use for this info... Chris...
;BEWARE! NO STACK!! processor 6502 include vcs.h org $F000 Start ; SEI ; Disable interrupts, if there are any. ; CLD ; Clear BCD math bit. ; LDX #$FF ; TXS ; Set stack to beginning. ; LDA #0 ;B1 STA 0,X ; DEX ; BNE B1 lda #0 sta PF0 sta PF1 sta PF2 STA COLUBK sta CTRLPF STA COLUPF sta GRP0 sta GRP1 sta HMCLR lda #14 sta COLUP0 sta COLUP1 lda #1 sta NUSIZ0 ;3 Cycles sta NUSIZ1 ;3 Cycles DrawLogo LDX #0 LDA #2 STA VSYNC ;Begin vertical sync. STA WSYNC ; First line of VSYNC STA WSYNC ; Second line of VSYNC. LDA #41 STA TIM64T LDA #0 STA CXCLR STA WSYNC ; Third line of VSYNC. STA VSYNC ; (0) DrawScreen LDA INTIM BNE DrawScreen ; Whew! STA WSYNC STA VBLANK ;End the VBLANK period with a zero. lda #255 sta ENAM0 ;GRP0 sta ENAM1 ;GRP1 ldy #100 nextmissiledemo: sta WSYNC nop nop nop nop nop nop nop nop nop sta RESM0 sta RESM1 sta RESM0 sta RESM1 sta RESM0 sta RESM1 sta RESM0 sta RESM1 sta RESM0 sta RESM1 dey bne nextmissiledemo lda #0 sta ENAM0 ;GRP0 sta ENAM1 ;GRP1 sta WSYNC ldy #96 nextblankline: sta WSYNC dey bne nextblankline STA VBLANK ; Make TIA output invisible, lda #35 sta TIM64T OverscanWait: lda INTIM bne OverscanWait JMP DrawLogo ;Continue forever. org $FFFC .word Start .word Start
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