**************************************************************************** * 3 Layer Sprite StarField * * Code By Andy Lucas,Alias Count Zero * * ------------------------------------------------------------------------ * * * * This is the standard type of starfield,it re-uses one sprite DMA channel * * a multiple number of times,the move routine is very short,and not hard * * to follow. * **************************************************************************** SECTION LOWMEM,CODE_C OPT C- MOVEM.L A0-A6/D0-D7,-(A7) MOVE.L A7,Stackpoint JSR Kill_OS JSR SetUp_Planes JSR SetUp_Sprite JSR Main JSR Help_OS MOVE.L Stackpoint,A7 MOVEM.L (A7)+,A0-A6/D0-D7 RTS **************************************************************************** * KILL OS * **************************************************************************** Kill_OS MOVE.L $4,A6 CLR.L D0 LEA GFXlib(PC),A1 JSR -552(A6) Open graphics library MOVE.L D0,GFXBase JSR -132(A6) LVO Forbid MOVE.W $DFF002,DMAsave MOVE.W $DFF01C,INTensave MOVE.W $DFF01E,INTrqsave MOVE.W #%0111111111111111,$DFF09A Switch INTENA off MOVE.W #%0111111111111111,$DFF096 Switch all DMA off MOVE.L #Copperlist,$DFF080 MOVE.W $DFF088,D0 MOVE.W #%1000001110100000,$DFF096 DMA:Cop/Bit/Sprite RTS **************************************************************************** * SETUP * **************************************************************************** SetUp_Planes LEA Planes,A0 Set only 1 Plane MOVE.L #Picture,D0 MOVE.W D0,6(A0) SWAP D0 MOVE.W D0,2(A0) RTS **************************************************************************** * SETUP STARS * **************************************************************************** SetUp_Sprite MOVE.L #Sprite,D0 Address of Stars LEA Sp_Ptr,A0 pointers in Coperlist MOVE.W D0,6(A0) Load high word SWAP D0 swap words MOVE.W D0,2(A0) Load low words MOVE.L #Sprite_Empty,D0 Empty Sprite LEA Sp_Ptr,A0 Pointers in copper ADD.L #8,A0 Point Past Sprite0 MOVE.L #6,D1 Loop Value Sp_Lp MOVE.W D0,6(A0) Load Blank Sprites Loop SWAP D0 MOVE.W D0,2(A0) SWAP D0 ADD.L #8,A0 Next pointer in Copper DBF D1,Sp_Lp Loop RTS **************************************************************************** * MAIN * **************************************************************************** Main CMPI.B #240,$DFF006 BNE.S Main ; MOVE.W #$000,$DFF180 Raster Time Monitor!! JSR Stars ; MOVE.W #$003,$DFF18 Try Removing both semi-colons BTST #6,$BFE001 BNE.S Main RTS **************************************************************************** * STARS * **************************************************************************** Stars MOVE.L #SpriteE-Sprite,D2 Length (N) of Star data block DIVU #(8*3),D2 No.Layers (3) MOVE.L #Sprite,A0 Address of stars Ch CMPI.B #$DF,1(A0) Reached far right of screen? BNE.S Mv No,branch MOVE.B #$38,1(A0) Yes,reset to far left Mv ADDQ.B #$1,1(A0) 1st layer speed ADDQ.B #$2,9(A0) 2nd layer speed ADDQ.B #$3,17(A0) 3rd layer speed ADD.L #24,A0 Next 3 stars DBF.W D2,Ch Loop N times RTS Cool Routine Huh? **************************************************************************** * HELP OS * **************************************************************************** Help_OS MOVE.W INTensave,D7 BSET #$F,D7 MOVE.W D7,$DFF09A Restore INTen MOVE.W INTrqsave,D7 BSET #$F,D7 MOVE.W D7,$DFF09C Restore INTrq MOVE.W DMAsave,D7 BSET #$F,D7 MOVE.W D7,$DFF096 Restore DMA MOVE.L GFXbase,A0 MOVE.L $26(A0),$DFF080 MOVE.L $4,A6 JSR -138(A6) LVO Permit RTS **************************************************************************** * COPPER * **************************************************************************** Copperlist Planes DC.L $00E00000,$00E20000 BPL1PTH/L Col DC.L $01800003,$01820000 COLOR0/1 Sp_Ptr DC.L $01200000,$01220000 Sprite0 PTH/L DC.L $01240000,$01260000 Sprite1 PTH/L DC.L $01280000,$012A0000 Sprite2 PTH/L DC.L $012C0000,$012E0000 Sprite3 PTH/L DC.L $01300000,$01320000 Sprite4 PTH/L DC.L $01340000,$01360000 Sprite5 PTH/L DC.L $01380000,$013A0000 Sprite6 PTH/L DC.L $013C0000,$013E0000 Sprite7 PTH/L Sp_Col DC.L $01A20999 COLOR 17 DC.L $01A40BBB COLOR 18 DC.L $01A80000 COLOR 19 DC.L $01001200,$01020000 BPLCON0/1 DC.L $01080000,$010A0000 BPL1/2MOD DC.L $00920030,$009400D8 DDFSTRT/DDFSTOP DC.L $008E1A64,$009039D1 DIWSTRT/DIWSTOP DC.L $FFFFFFFE **************************************************************************** * LABELS * **************************************************************************** INTrqsave DC.W 0 INTensave DC.W 0 DMAsave DC.W 0 GFXBase DC.L 0 SYSStackpoint DC.L 0 Stackpoint DC.L 0 GFXlib DC.B "graphics.library" Picture DCB.B 290*44,0 Sprite_Empty DCB.B 10,0 **************************************************************************** * STAR POS * 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$0446,$0506,$1000,$0000,$0688,$0706,$1000,$0000 dc.w $0899,$0906,$1000,$0000,$0ADD,$0B06,$1000,$0000 dc.w $0CEE,$0D06,$1000,$0000,$0EFF,$0F06,$1000,$0000 dc.w $10CD,$1106,$1000,$0000,$1267,$1306,$1000,$0000 dc.w $1443,$1506,$1000,$0000,$1664,$1706,$1000,$0000 dc.w $1823,$1906,$1000,$0000,$1A6D,$1B06,$1000,$0000 dc.w $1C4F,$1D06,$1000,$0000,$1E5F,$1F06,$1000,$0000 dc.w $2055,$2106,$1000,$0000,$2267,$2306,$1000,$0000 dc.w $2445,$2506,$1000,$0000,$2623,$2706,$1000,$0000 dc.w $2834,$2906,$1000,$0000,$2AF0,$2B06,$1000,$0000 dc.w $2CBC,$2D06,$1000,$0000 SpriteE dc.w $0000,$0000 END