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Hello World - Overkill Edition

What happens on a quiet Sunday when Github suggests making a "Hello
World" project!
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C64CD committed Sep 13, 2015
1 parent 1a8ea06 commit 65f3cf2be7ed3f6da180b4c26f36221583b04c42
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;
; HELLO GITHUB
;

; Code, graphics and music by TMR


; Notes: this source is formatted for the ACME cross assembler available
; from http://sourceforge.net/projects/acme-crossass/

; Everything is done before $2000 in memory, but $3fff is zeroed at the
; start of each frame so the border areas are clear apart from the
; hardware sprites.


; Memory Map
; $0801 - $0e3f program code/data
; $0e40 - $0fff sprites
; $1000 - $1bff music
; $1c00 - $1fff scrolling message


; Select an output filename
!to "hello_github.prg",cbm


; Pull in the binary data
* = $0e40
!binary "binary\c64cd_sprites.raw"

* = $1000
music !binary "binary\hymn_to_yezz.prg",,2


; Raster split positions
raster_1_pos = $00
raster_2_pos = $f9

; Label assignments
raster_num = $50
scroll_x = $51
scroll_pos = $52 ; two bytes used

sine_at = $54
scroll_colour = $55

scroll_line = $05e0
scroll_col_line = scroll_line+$d400

; Add a BASIC startline
* = $0801
!word code_start-2
!byte $40,$00,$9e
!text "2066"
!byte $00,$00,$00


; Entry point for the code
* = $0812

; Stop interrupts, disable the ROMS and set up NMI and IRQ interrupt pointers
code_start sei

lda #$35
sta $01

lda #<nmi_int
sta $fffa
lda #>nmi_int
sta $fffb

lda #<irq_int
sta $fffe
lda #>irq_int
sta $ffff

; Set the VIC-II up for a raster IRQ interrupt
lda #$7f
sta $dc0d
sta $dd0d

lda $dc0d
lda $dd0d

lda #raster_1_pos
sta $d012

lda #$1b
sta $d011
lda #$01
sta $d019
sta $d01a

; Initialise some of our own labels
lda #$01
sta raster_num
lda #$00
sta scroll_x

; Clear the screen RAM
ldx #$00
lda #$20
screen_clear sta $0400,x
sta $0500,x
sta $0600,x
sta $06e8,x
inx
bne screen_clear

; Reset the scroller
jsr scroll_reset

; Set up the music driver
lda #$00
jsr music+$00


; Restart the interrupts
cli

; Infinite loop - all of the code is executing on the interrupt
jmp *


; IRQ interrupt handler
irq_int pha
txa
pha
tya
pha

lda $d019
and #$01
sta $d019
bne int_go
jmp irq_exit

; An interrupt has triggered
int_go lda raster_num
cmp #$02
bne *+$05
jmp irq_rout2


; Raster split 1
irq_rout1 lda #$0e
sta $d020
lda #$06
sta $d021
lda #$00
sta $3fff

lda scroll_x
and #$03
asl
eor #$07
sta $d016
lda #$16
sta $d018

; Set up the sprites
lda #$ff
sta $d015
sta $d01b

ldx #$00
ldy #$00
set_sprite_x lda sprite_x_pos,x
sta $d000,y
iny
iny
inx
cpx #$08
bne set_sprite_x
lda sprite_x_msb
sta $d010

ldx #$00
ldy sine_at
set_sprite_y lda sprite_sinus,y
sta $d001,x
tya
sec
sbc #$0c
cpx #$04
bne *+$05
sec
sbc #$40
tay
inx
inx
cpx #$10
bne set_sprite_y

ldx #$00
lda #$38
hide_sprite_dp sta $07f8,x
inx
cpx #$08
bne hide_sprite_dp

lda #$1a
cmp $d012
bne *-$03

ldx #$00
set_sprite_dp lda sprite_dps,x
sta $07f8,x
lda sprite_colours,x
sta $d027,x
inx
cpx #$08
bne set_sprite_dp

; Play the music
jsr music+$03

; Set interrupt handler for split 2
lda #$02
sta raster_num
lda #raster_2_pos
sta $d012

; Exit IRQ interrupt
jmp irq_exit


; Raster split 2
irq_rout2

; Set interrupt handler for split 1
lda #$01
sta raster_num
lda #raster_1_pos
sta $d012


; Open the upper and lower borders
lda #$14
sta $d011

lda #$fc
cmp $d012
bne *-$03
lda #$1b
sta $d011


; Move scrolling message
ldx scroll_x
inx
cpx #$04
bne scr_xb

; Move the text line
ldx #$00
scroll_mover lda scroll_line+$01,x
sta scroll_line+$00,x
lda scroll_col_line+$01,x
sta scroll_col_line+$00,x
inx
cpx #$26
bne scroll_mover

; Copy a new character to the scroller
ldy #$00
scroll_mread lda (scroll_pos),y
bne scroll_okay
jsr scroll_reset
jmp scroll_mread

scroll_okay cmp #$80
bcc scroll_okay_2
and #$0f
sta scroll_colour
lda #$20

scroll_okay_2 sta scroll_line+$26
lda scroll_colour
sta scroll_col_line+$26

; Nudge the scroller onto the next character
inc scroll_pos+$00
bne *+$04
inc scroll_pos+$01

ldx #$00
scr_xb stx scroll_x


; Update the sprite movement
inc sine_at


; Restore registers and exit IRQ interrupt
irq_exit pla
tay
pla
tax
pla
nmi_int rti


; Subroutine to reset the scrolling message
scroll_reset lda #<scroll_text
sta scroll_pos+$00
lda #>scroll_text
sta scroll_pos+$01
rts


; Sprite data pointers and colours
sprite_x_pos !byte $38,$54,$70,$ac,$c8,$e4,$00,$1c
sprite_x_msb !byte $c0
sprite_dps !byte $3d,$3b,$3c,$39,$3f,$3e,$39,$3a
sprite_colours !byte $03,$03,$03,$0e,$0a,$0a,$0e,$0e


; Sprite movement sine table
sprite_sinus !byte $8c,$8f,$91,$94,$96,$99,$9c,$9e
!byte $a1,$a3,$a6,$a8,$ab,$ad,$b0,$b2
!byte $b5,$b7,$b9,$bc,$be,$c0,$c3,$c5
!byte $c7,$c9,$cb,$cd,$cf,$d1,$d3,$d5
!byte $d7,$d9,$da,$dc,$de,$df,$e1,$e3
!byte $e4,$e5,$e7,$e8,$e9,$ea,$ec,$ed
!byte $ee,$ef,$f0,$f0,$f1,$f2,$f2,$f3
!byte $f4,$f4,$f4,$f5,$f5,$f5,$f5,$f5

!byte $f5,$f5,$f5,$f5,$f5,$f5,$f4,$f4
!byte $f3,$f3,$f2,$f2,$f1,$f0,$ef,$ee
!byte $ed,$ec,$eb,$ea,$e9,$e8,$e6,$e5
!byte $e4,$e2,$e1,$df,$dd,$dc,$da,$d8
!byte $d6,$d5,$d3,$d1,$cf,$cd,$cb,$c8
!byte $c6,$c4,$c2,$c0,$bd,$bb,$b9,$b6
!byte $b4,$b2,$af,$ad,$aa,$a8,$a5,$a3
!byte $a0,$9d,$9b,$98,$96,$93,$91,$8e

!byte $8b,$89,$86,$84,$81,$7e,$7c,$79
!byte $77,$74,$72,$6f,$6d,$6a,$68,$65
!byte $63,$60,$5e,$5c,$59,$57,$55,$53
!byte $50,$4e,$4c,$4a,$48,$46,$44,$42
!byte $40,$3f,$3d,$3b,$39,$38,$36,$35
!byte $33,$32,$30,$2f,$2e,$2d,$2c,$2a
!byte $29,$28,$28,$27,$26,$25,$25,$24
!byte $23,$23,$23,$22,$22,$22,$22,$22

!byte $22,$22,$22,$22,$22,$22,$23,$23
!byte $24,$24,$25,$25,$26,$27,$28,$29
!byte $2a,$2b,$2c,$2d,$2e,$2f,$31,$32
!byte $34,$35,$37,$38,$3a,$3c,$3d,$3f
!byte $41,$43,$45,$47,$49,$4b,$4d,$4f
!byte $51,$53,$55,$58,$5a,$5c,$5f,$61
!byte $63,$66,$68,$6b,$6d,$70,$72,$75
!byte $77,$7a,$7c,$7f,$82,$84,$87,$89


; The all-important scrolling message - $00 wraps to the start and the
; values from $80 to $8f set the text colour
* = $1c00
scroll_text !byte $8f
!scr "So",$87,"Github",$8f,"reckoned I should make a"
!scr $81,$22,"Hello World",$22,$8f
!scr "project to get things started, but I got carried away and "
!scr "it accidentally turned into this little intro - "
!scr "6K uncompressed with sprite movements, open borders, music "
!scr "and still about 1K for scroll text!"
!scr " "

!byte $88
!scr "It has been, it should be noted, a"
!scr $8a,"particularly",$88,"quiet Sunday...!"
!scr " "

!byte $80
!scr "Coding, sprites and music by ",$8e,"T.M.R",$80,"with the "
!scr "latter being a conversion of the awesome"
!scr $8e,$22,"Hymn To Yezz",$22
!scr " "

!byte $85
!scr "I'll just pause for a moment to plug the C64CD website at "
!byte $8d
!scr "C64CrapDebunk.Wordpress.com"
!byte $85
!scr "and that's pretty much everything said and done, so we "
!scr "might as well wrap this scroller to the beginning..."
!scr " "

!byte $00
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