; BADUK v2.0
; 2011 (c) JrezCorp Team
;
; ASM6502
;
    .list
    .inesprg 1 ; 1 PRG
    .ineschr 1 ; 1 CHR
    .inesmir 0 ; V-mirroring
    .inesmap 0 ; 0-map (NMAP)

; MEMORY MAP
;
; 0x0000 - 0x04FF - arrays (0x0000-0x00FF - zero page, 0x0100-0x01FF - stack, 0x0200-0x02FF - sprite memmory)
; 0x0500 - 0x07FF - variables
; 0x0800 - 0x1FFF - mirrors of 0x0000 - 0x04FF
; 0x2000 - 0x2007 - PPU registers
; 0x2008 - 0x3FFF - mirrors of 0x2000 - 0x2007
; 0x4000 - 0x401F - 2A03 (APU) registers
; 0x4020 - 0x5FFF - mapper registers (not used)
; 0x6000 - 0x7FFF - SRAM
; 0x8000 - 0xFFFF - PRG ROM

; VARIABLES AND ARRAYS

stack = $0100 ; (size = 256)
sprite_mem = $0200 ; (size = 256)
nmi_hit = $0500 ; (size = 1)
temp = $0501 ; (size = 1)
temp_2 = $0502 ; (size = 1)
joy1stat = $0503 ; (size = 1)
joy1a = $0504 ; (size = 1)
joy1b = $0505 ; (size = 1)
joy1select = $0506 ; (size = 1)
joy1start = $0507 ; (size = 1)
joy1up = $0508 ; (size = 1)
joy1down = $0509 ; (size = 1)
joy1left = $050A ; (size = 1)
joy1right = $050B ; (size = 1)
dig = $050C
digits = $050E

    .bank 0
    .org $8000

; PRG ROM

main:
; show logo
    jsr jcorp
    lda #0
mainloop:
    beq mainloop

inc_digits:
    ldx #3
id_loop:
    lda digits,x
    adc #0
    cmp #10
    bmi id_low10
    clc
    sbc #9
    sec
id_low10:
    sta digits,x
    dex
    bne id_loop
    rts
mul2_digits:
    ldx #3
md_loop:
    lda digits,x
    adc digits,x
    cmp #10
    bmi md_low10
    clc
    sbc #9
    sec
md_low10:
    sta digits,x
    dex
    bne md_loop
    rts

; jcorp logo
jcorp:
; PPU is turned off
; setup palette
    lda #$3f
    sta $2006
    lda #0
    sta $2006
    lda #13
    sta $2007
    lda #45
    sta $2007
    lda #38
    sta $2007
    lda #40
    sta $2007
; clearing attributes
    lda #$23
    sta $2006
    lda #$c0
    sta $2006
    ldx #64
    lda #0
jcorp_loop0:
    sta $2007
    dex
    bne jcorp_loop0
; filling nametable
    lda #$20
    sta $2006
    sta $2006
;------------- clear digits
    ldx #3  ;digits count
    lda #0  ;initial value
cl_loop:
    sta digits,x
    dex
    bne cl_loop
;------------------- test value
    lda #73
    sta dig
;-------------------
    ldy #8  ;bits
convert_loop:
    clc
    jsr mul2_digits
    clc
    rol dig
    jsr inc_digits
    dey
    bne convert_loop

    ldx #3
    ldy #1
my_loop:
    lda digits,y
    clc
    adc #$30
    sta $2007
    iny
    dex
    bne my_loop


; turn on PPU
    jsr vwait
    lda #%00000000
    sta $2000
; show bg, no clipping
    lda #%00001010
    sta $2001
; clear scroll
clear_scroll:
    lda #0
    sta $2005
    sta $2005
    sta $2006
    sta $2006
    rts
; wait for vblank starts
vwait_start:
    lda $2002
    bpl vwait_start
    rts
; wait for vblank ends and clear scroll
vwait_end:
    jsr vwait_end_wc
    jsr clear_scroll
    rts
; wait for vblank ends
vwait_end_wc:
    lda $2002
    bmi vwait_end
    rts
; wait for a vblank
vwait:
    jsr vwait_wc
    jsr clear_scroll
    rts
; wait for a vblank (scroll not cleared)
vwait_wc:
    jsr vwait_start
    jsr vwait_end_wc
    rts
; entry point
start:
; turn off PPU
    lda #0
    sta $2000
    sta $2001
; disable interrupts
    sei
; wait for two vblanks
    jsr vwait_wc
    jsr vwait_wc
; reset stack pointer
    ldx $ff
    txs
; goto main
    jmp main
nmi:
    php
    pha
    txa
    pha
    tya
    pha
    lda #1
    sta nmi_hit
    pla
    tay
    pla
    tax
    pla
    plp
    rti

; ignore any irq
irq:
    rti
; DATA
jcorp_table:
    .db 0,171,2,1,0,14,4,1,6,1,8,1,0,7,10,1
    .db 0,2,12,1,0,2,14,1,16,1,18,1,0,7,20,1
    .db 22,1,24,1,26,1,28,1,30,1,96,1,98,1,100,1
    .db 0,6,102,1,104,1,106,1,108,1,110,1,112,1,114,1
    .db 116,1,118,1,120,1,0,6,122,1,124,1,126,1,128,1
    .db 130,1,132,1,134,1,136,1,138,1,140,1,0,13,142,1
    .db 144,1,146,1,0,14,148,1,150,1,0,163

    .bank 1
    .org $FFFA
; POINTERS
    .dw nmi, start, irq
    .bank 2
    .org $0000
; CHR ROM
    .incbin "rom.chr"