Commodore Disk User Volume 4 #1

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Assembly Source File | 2022-10-26 | 7KB | 334 lines

; ; Smooth scroller, Copyright A.Millett ; *=$9c00 ; vic = 53248 ; Vic chip sprptrs = 33784 hibits = vic + 16 ; MSB of sprite posns zptr = $fb zptr2= $fd zmsgptr = $fb kbhit = 198 ; Set if char typed. vdu = 32768 ; Loc of screen colram = $d800 ; Loc of color ram ; ; Jump vector table.. dosmooth. jmp main resetsmooth. jmp init jspecialfx. jmp specialfx jdorotate. jsr dorotatechar jwait1scr. jmp wait1scr jfillvdu. jmp fillvdu jdo1dot. jmp do1dot ; .byte 0,0,0 .byte 0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0 .byte 0,0,0,0,0,0,0,0 ; Ok, flags start at $9c28 ; msgptr. ; If any scroll of edge, this is ptr to new spr .word $9000 msgloc. .word $9000 chrsetloc. ; Loc of user def char set .word $8800 index. .byte 0 rmarg. ; Reset pos for new spr .byte 112 lmarg. .byte 24 hspacing. ; Horizontal spacing of sprites. .byte 46 scolor. ; Sprite color .byte 1 widemode. ; Double width sprites .byte 255 wiggleflag. ; Set for jumping scroll .byte 0 speed. ; Scroll speed in x/50 sec/dot .byte 0 sproffset. ; Start of sprites .byte 127 hline. ; Screen line for scroll .byte 224 moveby2flag. ; Move scroll by 2 if bit 7 set .byte 0 fillchar. ; Char for screen fill .byte 87 tickchar. ; Char used for 'tick' fx .byte 209 rotchar. ; Char rotated for moving background .byte 87 rotlen. ; No of pixels to rotate .byte 7 fillcolor. ; Color for screen fill .byte 0 mask. .byte 1,2,4,8,16,32,64,128 wiggle. ; Vert wiggle factor .byte 7,5,4,3,2,1,1,0,0,0,1,1,2,3,4,5 ; ; main. mainloop. jsr dorotatechar ; Rotate scrolling background ldx speed ; First wait for a time & sync to screen wloop. jsr wait1scr dex bpl wloop jsr do1dot ; Scroll message 1 dot.. bit moveby2flag ; 2 dot move ? bpl no2move ; No.. jsr do1dot ; Scroll message 1 more dot.. no2move. lda kbhit beq mainloop ; No key hit, reloop.. rts ; Ok, done! ; do1dot. ; Scroll 1 dot left, ldx #$00 ; Index into sprites ldy #$00 sty index more. lda vic,x bne nohi ; No overflow.. lda mask,y ; Get hi bit and hibits bne nonew ; Set, so clear.. jsr newsprite ; Start a new sprite clc bcc nohi nonew. ; Lo byte overflow, clr hi bit lda mask,y eor # $ff ; Calc mask for hi bit and hibits sta hibits nohi. ; Ok, now set vert pos dec vic,x ; Move spr left ldy index lda #0 bit wiggleflag ; Do we wiggle ? bpl nowiggle lda vic,x ; use hpos as index to wiggle and # $0f tay lda wiggle,y nowiggle. clc ; Now add in norm vert line adc hline sta vic+1,x ; Store vert pos for sprite. inc index ; Ok, next sprite.. ldy index inx inx cpy # 8 bne more ; next sprite.. rts ; Ok, done! ; newsprite. ; Start a new sprite lda rmarg ; Start new sprite far right sta vic,x lda mask,y ora hibits ; Set hi bit sta hibits nextmsg. ; Advance message pointer inc msgptr bne getmsg inc msgptr+1 getmsg. ; Get char from msg string lda msgptr ; Mov ptr to zero page sta zmsgptr lda msgptr+1 sta zmsgptr+1 ldy #0 lda (zmsgptr),y ; Get msg char bne new2 ; Not null yet, so print.. lda msgloc ; End of message, so reset msg to start sta msgptr lda msgloc+1 sta msgptr+1 clc bcc getmsg new2. bpl normlet ; No special effects cmp #128 ; Toggle wiggle ? bne new3 lda #$80 eor wiggleflag sta wiggleflag clc bcc nextmsg ; Another msg char.. new3. cmp #129 ; Toggle 2 dot speed? bne new4 lda #$80 eor moveby2flag sta moveby2flag clc bcc nextmsg ; Another msg char.. new4. and #$1f sta speed clc bcc nextmsg ; Another msg char.. normlet. ; Ok norm letter in acc, store in sprite ptr ldy index clc adc sproffset sta sprptrs,y jsr specialfx ; Move line in ball chr rts ; specialfx. ; Move line in ball chr tya pha ; stash y reg lda tickchar ; Character to tick jsr setchrptr ; Set up (zptr) to char ldy #3 lda (zptr),y pha iny lda (zptr),y dey sta (zptr),y pla iny sta (zptr),y pla tay rts ; dorotatechar. ; Rotate special char vertically for effect tya pha ; stash y reg lda rotchar ; Character to rotate jsr setchrptr ; Set up (zptr) to char ldy rotlen ; No to rotate lda (zptr),y ; Stash top one pha spec1. dey ; Ripple bytes down.. lda (zptr),y iny sta (zptr),y dey bne spec1 pla sta (zptr),y ; Reget top val and put at bottom pla ; Reget y reg tay rts ; setchrptr. ; Set up (zptr) to point to loc of char in Acc ldy #0 ; Clr hi byte zptr sty zptr+1 asl a ; Mult char by 8 rol zptr+1 asl a rol zptr+1 asl a rol zptr+1 clc ; Add in chr address to chrset location adc chrsetloc sta zptr lda zptr+1 adc chrsetloc+1 sta zptr+1 rts ; fillvdu. ; Fill vdu with (fillchar) jsr setcolor ; Fill color ram lda fillchar ldy #0 fill1. sta vdu,y sta vdu+256,y sta vdu+512,y sta vdu+768,y iny bne fill1 rts ; setcolor. ; Fill color ram with (fillcolor) lda fillcolor ldy #0 fill2. sta colram,y sta colram+256,y sta colram+512,y sta colram+768,y iny bne fill2 rts ; wait1scr. ; Wait for screen to finish lda vic+18 ; Current raster val cmp #250 bcc wait1scr wait2. lda vic+18 ; Current raster val cmp #250 bcs wait2 rts ; init. ; Initialise sprite positions and switch them on lda #0 sta hibits sta wiggleflag ; No wiggle to start sta moveby2flag ; Slow to start lda msgloc ; Reset message pointer sta msgptr lda msgloc+1 sta msgptr+1 ldx #0 ldy #0 lda lmarg ; Xpos index lo sta zptr stx zptr+1 ; Xpos hi init1. lda hline sta vic+1,x ; Set Y pos of sprite lda zptr sta vic,x ; Set sprite X pos lo byte lda zptr+1 ; Any hi bit for sprite? beq init2 ; Leave hi bit clr lda mask,y ; Set sprite(y) hi bit ora hibits sta hibits init2. lda scolor ; Ok, Set color for sprite sta vic+39,y lda sproffset clc adc #1 ; all sprite start spc sta sprptrs,y lda zptr clc adc hspacing sta zptr bcc init3 inc zptr+1 init3. inx inx iny cpy #8 bne init1 lda widemode sta vic+29 lda #255 sta vic+21 ; Switch on sprites rts ;