; Display Example 16. -- Dual Playfield Scrolling -- ; Display is 320x256 ( 40x256x6 bytes ) in dual playfield mode. ; Playfield 1 is 320x512x3 ( 40x512x3 bytes ) ; Playfield 2 is 640x256x3 ( 80x256x3 bytes ) ; Bitplane Modulos = bit plane width - Display width - 2 = 80-40-2 = 38 bytes include hardware.i include HW_Macros.i include HW_Start.i ; First, 'poke' address of playfield 1's bit planes into Copper list. Use a ;loop to do this Main COPBPLC CopPlanes,pf1,(320/8)*512,3 ; Now 'poke' address of playfield 2's bit planes into Copper list. COPBPL CopPlanes2,pf2,(640/8)*256,3 ; Set colours for second playfield manually lea pf2+80*256*3,a0 a0->colour data moveq.l #8-1,d0 num colours - 1 lea CopColours2,a1 a1->into Copper list colr_loop1 move.w (a0)+,2(a1) copy colour addq.l #4,a1 next register dbra d0,colr_loop1 ; Define address of Copper List STARTCOP #MyCopper ; Enable bitplane and Copper DMA. move.w #SETIT!DMAEN!COPEN!BPLEN,DMACON(a5) ; Install vertical blank interrupt handler and enable it. move.l #NewLevel3,$6c install move.w #SETIT!INTEN!VERTB,INTENA(a5) ; Wait for user to press the left mouse button mouse btst #6,CIAAPRA bne.s mouse ; And exit. rts ; ************************ ; * Vert Blank Interrupt * ; ************************ ; This handler first calls a routine that sets up the bit plane pointers and ;scroll values according to the value stored in 'Scroll'. Second, a routine ;is called that changes the value stored in 'Scroll'. NewLevel3 lea $dff000,a5 a5->hardware base bsr DoScroll_H horizontal scroll bsr DoScroll_V vertical scroll bsr UpdateScroll_H update horiz count move.w INTREQR(a5),d0 get bits and.w #VERTB!COPER!BLIT,d0 move.w d0,INTREQ(a5) clear request rte back to user mode ; *************************** ; * Scroll The Bitplane * ; *************************** ; Uses the value stored in scroll to determine the position of the bip plane DoScroll_H move.l Scroll_H,d0 num pixels to scroll divu #16,d0 ; Now high word of d0 contains scroll value in pixels and the low word the ;number of words to scroll. The number of words must be converted into the ;number of bytes: asl.w #1,d0 x2 moveq.l #0,d1 move.w d0,d1 d1=num bytes swap d0 get num bits moveq.l #15,d2 sub.w d0,d2 make a copy move.w d2,d0 asl.w #4,d0 or.w #$f,d0 ; At this point d0.w contains the scroll value and d1 the number of bytes ;to add to the start address of the bit plane data. Initialise the scroll ;value and bit plane pointers in the copper list move.w d0,CopScroll+2 scroll values add.l #pf2,d1 d1=bpl start addr moveq.l #3-1,d0 bpl counter - 1 lea CopPlanes2,a0 a0->into Copper StuffBpls move.w d1,6(a0) low word of address swap d1 move.w d1,2(a0) high word of address swap d1 add.l #80*256,d1 addr of next plane addq.l #8,a0 next pointer in list dbra d0,StuffBpls rts ; *************************** ; * Update Scroll Value * ; *************************** ; Continually counts from 0 to 320 and back again. A separate routine is used ;to convert the scroll value and modify the Copper list UpdateScroll_H move.l Scroll_H,d0 move.l direction_H,d1 move.l terminate_H,d2 add.l d1,d0 bump counter move.l d0,Scroll_H save new value cmp.l d0,d2 change direction? bne.s no_change no, exit routine move.l spare_H,terminate_H switch dirn limits move.l d2,spare_H neg.l d1 move.l d1,direction_H change direction no_change rts ; ********************************* ; * Scroll Playfield 1 Vertically * ; ********************************* DoScroll_V move.l Counter,d0 move.l direction_V,d1 move.l terminate_V,d2 add.l d1,d0 bump counter move.l d0,Counter save new value cmp.l d0,d2 change direction? bne.s no_change_V no, exit routine move.l spare_V,terminate_V switch dirn limits move.l d2,spare_V neg.l d1 move.l d1,direction_V change direction no_change_V mulu #40,d0 calculate offset add.l #pf1,d0 form start address bsr PutPointers update Copper list rts ; ****************************** ; * Poke playfield 1 addresses * ; * into Copper list * ; ****************************** ; Entry d0=start address of 1st bit planes data PutPointers moveq.l #3-1,d1 number of bit planes - 1 lea CopPlanes,a0 a0->into Copper list put_loop move.w d0,6(a0) low word of address swap d0 move.w d0,2(a0) high word of address swap d0 add.l #40*512,d0 addr of next bit plane addq.l #8,a0 next pointer in Copper list dbra d1,put_loop rts ; *************************** ; * Program Variables * ; *************************** Scroll_H dc.l 0 direction_H dc.l 1 1=right, -1=left terminate_H dc.l 320 change direction at ... spare_H dc.l 0 Counter dc.l 0 offset direction_V dc.l 1 1=up, -1=down terminate_V dc.l 255 change direction at ... spare_V dc.l 0 ; *************************** ; * CHIP Memory Data * ; *************************** ;section data custom,chip section fish,data_c MyCopper CWAIT 0,38 wait for line 40 CMOVE DIWSTRT,$2c81 PAL -- 256 lines CMOVE DIWSTOP,$2cc1 CMOVE DDFSTRT,$0030 LoRes + scroll CMOVE DDFSTOP,$00d0 CMOVE BPL1MOD,-2 modulo = -2 bytes CMOVE BPL2MOD,38 modulo = 38 bytes CMOVE BPLCON0,$6600 6 bitplanes, DBPLF CopScroll CMOVE BPLCON1,$000f Scroll values CMOVE BPLCON2,$0000 Ignore priority CopPlanes CMOVE BPL1PTH,0 Bit plane pointers CMOVE BPL1PTL,0 filled in by the CMOVE BPL3PTH,0 CMOVE BPL3PTL,0 CMOVE BPL5PTH,0 CMOVE BPL5PTL,0 CopColours CMOVE COLOR00,$0000 The colours will be CMOVE COLOR01,$0000 filled in by the CMOVE COLOR02,$0000 program! CMOVE COLOR03,$0000 CMOVE COLOR04,$0000 CMOVE COLOR05,$0000 CMOVE COLOR06,$0000 CMOVE COLOR07,$0000 CopPlanes2 CMOVE BPL2PTH,0 Bit plane pointers CMOVE BPL2PTL,0 filled in by the CMOVE BPL4PTH,0 program! CMOVE BPL4PTL,0 CMOVE BPL6PTH,0 CMOVE BPL6PTL,0 CopColours2 CMOVE COLOR08,$0000 CMOVE COLOR09,$0000 CMOVE COLOR10,$0000 CMOVE COLOR11,$0000 CMOVE COLOR12,$0000 CMOVE COLOR13,$0000 CMOVE COLOR14,$0000 CMOVE COLOR15,$0000 CEND end of list pf1 incbin 'pic5.bm' pf2 incbin 'pic6.bm' end