** CODE HORIZONTAL SCROLLER ** CODER MARC.B ; this is a basic horizontal scroller ; which seems to have a slight problem ; when the screen reaches the end and restars ; the display jumps down by one line i think this ; should be pretty easy to overcome by repeating ; the first screen at the end of the scroll and resetting ; the bitplane pointers when this is being displayed so ; preventing the display from wrapping up by one line ; ( haven't tried it yet but it should work ) ****************************************** * SYSTEM OFFSETS * ****************************************** execbase equ 4 openlibrary equ -408 closelibrary equ -414 allocmem equ -198 freemem equ -210 forbid equ -132 permit equ -138 copymem equ -624 *** constants *** chip equ 2 clear equ $10000 ****************************************** * INCLUDE FILE * ****************************************** include source:include/hardware.i lea $dff000,a5 ;custom base address ********************************************************** * OPEN GFX LIBRARY AND SAVE SYSTEM COPPER * ********************************************************** move.l execbase,a6 move.l #gfxname,a1 moveq #0,d0 jsr openlibrary(a6) tst d0 beq the_end move.l d0,gfxbase move.l d0,a0 move.l 38(a0),systemcopper **************************************************** * ALLOCATE MEMORY FOR BIT PLANES * **************************************************** move.l execbase,a6 move.l #(640/8*256)*3,d0 ;memory for 2 bitplanes move.l #chip+clear,d1 ;chip memory and wipe it jsr allocmem(a6) tst d0 ;fail beq exit ;yep exit move.l d0,bitbase ;save pointer **************************************************** * COPY SCREEN TO DISPLAY RAM * **************************************************** move.l execbase,a6 lea screen,a0 move.l bitbase,a1 move.l #(640/8*256)*3,d0 jsr copymem(a6) ****************************************************** * SET UP CUSTOM FLAGS * ****************************************************** clr.l offset clr.b counter move.w #$ff,delay *************************************************************** * START CUSTOM COPPER LIST * *************************************************************** move.l bitbase,d0 bsr load_pointers move.l #copper,COP1LCH(a5) move.l #0,COPJMP1(a5) move.l execbase,a6 jsr forbid(a6) ************************************************************* * MAIN CODE LOOP * ************************************************************* wait move.l VPOSR(a5),d0 ;read current beam position and.l #$0001ff00,d0 ;mask all but the vertical pos lsr.l #8,d0 cmp.w #$0106,d0 ;wait for end of display bne wait bsr scroll_display btst #6,CIAAPRA ;check left mouse button beq clean_up ;end if pressed bra wait ********************************************************** * RESTORE SYSTEM * ********************************************************** clean_up move.l systemcopper,COP1LCH(a5) move.l #0,COPJMP1(a5) move.l execbase,a6 jsr permit(a6) move.l execbase,a6 ;free bitplane memory move.l #(640/8*256)*3,d0 move.l bitbase,a1 jsr freemem(a6) exit move.l gfxbase,a1 ;close the graphics library move.l execbase,a6 jsr closelibrary(a6) the_end rts ;exit from program ***************************************************************** * LOAD BITPLANE AND SPRITE POINTERS INTO COPPER LIST * ***************************************************************** load_pointers lea copper,a0 ;d0 is loaded with the bitplane address move.w d0,6(a0) ;before this routine is called swap d0 move.w d0,2(a0) swap d0 add.l #$5000,d0 move.w d0,14(a0) swap d0 move.w d0,10(a0) swap d0 add.l #$5000,d0 move.w d0,22(a0) swap d0 move.w d0,18(a0) swap d0 rts ******************************************************** * SCROLL DISPLAY * ******************************************************** scroll_display cmpi.b #40,counter ;reached end beq reset_pointer ;yes ! reset and begin again scroll cmpi.w #0,delay ;finished scroll beq update_pointer ;yes ! update pointers subi.w #$11,delay ;no ! scroll some more rts reset_pointer move.l #0,offset ;this routine just resets move.b #0,counter ;the counters and reloads move.l bitbase,d0 ;the original bitplane pointers bra load_pointers update_pointer add.l #2,offset ;this routine increments the move.l bitbase,d0 ;bitplane pointer and the word add.l offset,d0 ;counter then resets the delay move.w #$ff,delay add.b #1,counter bra load_pointers *********************************************************** * CUSTOM COPPER LIST * *********************************************************** SECTION copper.list,CODE_C copper dc.w BPL1PTH,0000 ;bitplane pointers dc.w BPL1PTL,0000 dc.w BPL2PTH,0000 dc.w BPL2PTL,0000 dc.w BPL3PTH,0000 dc.w BPL3PTL,0000 sprite.pointers dc.w SPR0PTH,0000 dc.w SPR0PTL,0000 ;sprite 0 pointer dc.w SPR1PTH,0000 dc.w SPR1PTL,0000 ;sprite 1 pointer dc.w SPR2PTH,0000 dc.w SPR2PTL,0000 ;sprite 2 pointer dc.w SPR3PTH,0000 dc.w SPR3PTL,0000 ;sprite 3 pointer dc.w SPR4PTH,0000 dc.w SPR4PTL,0000 ;sprite 4 pointer dc.w SPR5PTH,0000 dc.w SPR5PTL,0000 ;sprite 5 pointer dc.w SPR6PTH,0000 dc.w SPR6PTL,0000 ;sprite 6 pointer dc.w SPR7PTH,0000 dc.w SPR7PTL,0000 ;sprite 7 pointer display dc.w DIWSTRT,$2c81 dc.w DIWSTOP,$2bc1 dc.w BPLCON0,$0200 dc.w BPLCON2,$0000 dc.w DDFSTRT,$0030 dc.w DDFSTOP,$00d0 dc.w BPLCON1 delay dc.w $0000 dc.w BPL1MOD,$0026 dc.w BPL2MOD,$0026 colour_map dc.w COLOR00,$0000 ;background colour black dc.w COLOR01,$0fff ;colour 1 dc.w COLOR02,$0b52 ;colour 2 dc.w COLOR03,$0a42 ;colour 3 dc.w COLOR04,$0a42 dc.w COLOR05,$0932 dc.w COLOR06,$0832 dc.w COLOR07,$0822 dc.l $2c01fffe ;wait for line 44 dc.w BPLCON0,$3200 ;turn on bit planes dc.l $fffffffe ;wait for the impossible endcopper copperlen equ endcopper-copper ************************************************************ * VARIABLES * ************************************************************ gfxbase dc.l 0 bitbase dc.l 0 copperbase dc.l 0 systemcopper dc.l 0 offset dc.l 0 counter dc.b 0 gfxname dc.b 'graphics.library',0 screen incbin graphics/h_scroll.bmap end