928 lines
12 KiB
ArmAsm
928 lines
12 KiB
ArmAsm
.segment "HEADER"
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INES_MAPPER = 0
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INES_MIRROR = 1
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INES_SRAM = 0
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.byte 'N', 'E', 'S', $1A
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.byte $02
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.byte $01
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.byte INES_MIRROR
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.byte (INES_MAPPER & %11110000)
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.byte $0, $0, $0, $0, $0, $0, $0, $0
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.segment "TILES"
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.incbin "background.chr"
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.incbin "sprite.chr"
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.segment "VECTORS"
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.word nmi
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.word reset
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.word irq
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.segment "CODE"
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reset:
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sei
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lda #0
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sta $2000
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lda #0
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sta $2001
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sta $4015
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sta $4010
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lda #40
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sta $4017
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cld
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ldx #$FF
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txs
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bit $2002
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:
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bit $2002
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bpl :-
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lda #0
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ldx #0
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:
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sta $0000, X
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sta $0100, X
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sta $0200, X
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sta $0300, X
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sta $0400, X
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sta $0500, X
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sta $0600, X
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sta $0700, X
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inx
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bne :-
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lda #255
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ldx #0
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:
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sta oam, X
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inx
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inx
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inx
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inx
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bne :-
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:
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bit $2002
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bpl :-
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lda #%10101000 ; NMI enable, 8x16 sprites, ignored due to 8x16 mode
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sta $2000
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jmp main
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.segment "ZEROPAGE"
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nmi_lock: .res 1
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nmi_count: .res 1
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nmi_ready: .res 1
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nmt_update_len: .res 1
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scroll_x: .res 1
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scroll_y: .res 1
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scroll_nmt: .res 1
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temp: .res 1
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.segment "BSS"
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nmt_update: .res 256
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palette: .res 32
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.segment "OAM"
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oam: .res 256
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.segment "CODE"
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nmi:
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pha
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txa
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pha
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tya
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pha
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lda nmi_lock
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beq :+
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jmp @nmi_end
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:
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lda #1
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sta nmi_lock
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lda nmi_ready
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bne :+
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jmp @ppu_update_end
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:
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cmp #2
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bne :+
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lda #%00000000
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sta $2001
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ldx #0
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stx nmi_ready
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jmp @ppu_update_end
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:
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ldx #0
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stx $2003
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lda #>oam
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sta $4014
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lda #%10101000 ; NMI enable, 8x16 sprites, ignored due to 8x16 mode
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sta $2000
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lda $2002
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lda #$3F
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sta $2006
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stx $2006
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ldx #0
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:
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lda palette, X
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sta $2007
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inx
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cpx #32
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bcc :-
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ldx #0
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cpx nmt_update_len
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bcs @scroll
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@nmt_update_loop:
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lda nmt_update, X
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sta $2006
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inx
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lda nmt_update, X
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sta $2006
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inx
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lda nmt_update, X
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sta $2007
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cpx nmt_update_len
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bcc @nmt_update_loop
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lda #0
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sta nmt_update_len
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@scroll:
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lda scroll_nmt
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and #%00000011
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ora #%10101000
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sta $2000
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lda scroll_x
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sta $2005
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lda scroll_y
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sta $2005
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lda #%00011110
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sta $2001
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ldx #0
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stx nmi_ready
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@ppu_update_end:
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lda #0
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sta nmi_lock
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@nmi_end:
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pla
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tay
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pla
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tax
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pla
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rti
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.segment "CODE"
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irq:
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rti
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.segment "CODE"
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ppu_update:
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lda #1
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sta nmi_ready
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:
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lda nmi_ready
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bne :-
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rts
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ppu_skip:
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lda nmi_count
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:
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cmp nmi_count
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beq :-
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rts
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ppu_off:
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lda #2
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sta nmi_ready
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:
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lda nmi_ready
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bne :-
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rts
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ppu_address_tile:
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lda $2002
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tya
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lsr
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lsr
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lsr
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ora #$20
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sta $2006
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tya
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asl
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asl
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asl
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asl
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asl
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sta temp
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txa
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ora temp
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sta $2006
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rts
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ppu_update_tile:
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pha
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txa
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pha
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ldx nmt_update_len
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tya
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lsr
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lsr
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lsr
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ora #$20
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sta nmt_update, X
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inx
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tya
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asl
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asl
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asl
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asl
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asl
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sta temp
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pla
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ora temp
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sta nmt_update, X
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inx
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pla
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sta nmt_update, X
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inx
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stx nmt_update_len
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rts
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ppu_update_byte:
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pha
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tya
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pha
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ldy nmt_update_len
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txa
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sta nmt_update, Y
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iny
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pla
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sta nmt_update, Y
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iny
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pla
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sta nmt_update, Y
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iny
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sty nmt_update_len
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rts
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PAD_A = $01
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PAD_B = $02
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PAD_SELECT = $04
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PAD_START = $08
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PAD_U = $10
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PAD_D = $20
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PAD_L = $40
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PAD_R = $80
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.segment "ZEROPAGE"
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gamepad: .res 1
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.segment "CODE"
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; gamepad_poll: this reads the gamepad state into the variable labelled "gamepad"
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; This only reads the first gamepad, and also if DPCM samples are played they can
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; conflict with gamepad reading, which may give incorrect results.
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gamepad_poll:
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; strobe the gamepad to latch current button state
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lda #1
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sta $4016
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lda #0
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sta $4016
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; read 8 bytes from the interface at $4016
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ldx #8
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:
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pha
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lda $4016
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; combine low two bits and store in carry bit
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and #%00000011
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cmp #%00000001
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pla
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; rotate carry into gamepad variable
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ror
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dex
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bne :-
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sta gamepad
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rts
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.segment "RODATA"
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level:
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1
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.byte 0,1,0,0,1,0,0,0,0,0,0,0,1,1,1,1
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1
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.byte 0,1,0,0,1,0,0,0,0,0,0,0,1,1,1,1
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.byte 0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,1,1,1,1,1,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0
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.byte 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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metatiles:
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.byte 0,0,0,0,0
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.byte 3,4,5,6,1
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example_palette:
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.byte $0F,$00,$3D,$20 ; greyscale
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.byte $0F,$09,$1A,$16 ; grass
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.byte $0F,$15,$26,$37 ; bg0 purple/pink
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.byte $0F,$09,$19,$29 ; bg1 green
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.byte $0F,$01,$11,$21 ; bg2 blue
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.byte $0F,$00,$10,$30 ; bg3 greyscale
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.byte $0F,$18,$28,$38 ; sp0 yellow
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.byte $0F,$14,$24,$34 ; sp1 purple
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.byte $0F,$1B,$2B,$3B ; sp2 teal
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.byte $0F,$12,$22,$32 ; sp3 marine
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.segment "ZEROPAGE"
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buttons: .res 1
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player_pos_x: .res 1
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player_pos_y: .res 1
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player_vel_x: .res 1
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player_vel_y: .res 1
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cursor_x: .res 1
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cursor_y: .res 1
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temp_x: .res 1
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temp_y: .res 1
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temp_mul: .res 1
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var_m: .res 1
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var_n: .res 1
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var_o: .res 1
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var_p: .res 1
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jump_pressed_last_frame: .res 1
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frame_counter: .res 1
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.segment "CODE"
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main:
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ldx #0
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:
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lda example_palette, X
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sta palette, X
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inx
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cpx #32
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bcc :-
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jsr setup_background
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jsr ppu_update
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lda #$40
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sta cursor_x
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sta cursor_y
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lda #0
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sta frame_counter
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jsr init_objects
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@loop:
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lda frame_counter
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clc
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adc #1
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sta frame_counter
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jsr controller
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jsr movement
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@draw:
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jsr update_background
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jsr draw_player
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jsr ppu_update
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jmp @loop
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draw_player:
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lda player_pos_y
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sec
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sbc #9
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sta oam + (4 * 0) + 0
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sta oam + (4 * 1) + 0
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lda player_pos_x
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sta oam + (4 * 1) + 3
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sec
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sbc #8
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sta oam + (4 * 0) + 3
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rts
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init_objects:
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lda #0
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sta var_n
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ldx #0
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:
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lda var_n
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clc
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adc #8
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sta var_n
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sta player_pos_y, X ; Set Y position
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sta player_pos_x, X ; Set X position
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txa
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lsr
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lsr
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sta oam+1, X
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inx
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inx
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inx
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inx
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cpx #(8*4)
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bne :-
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lda #0
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sta player_vel_x
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sta player_vel_y
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rts
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draw:
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@end:
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rts
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movement:
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; Horizontal velocity
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ldx #0
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jsr btn_right
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cmp #0
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beq :+
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ldx #1
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lda #3
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sta player_vel_x
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:
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jsr btn_left
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cmp #0
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beq :+
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ldx #1
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lda #253
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sta player_vel_x
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:
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cpx #1
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beq @end
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lda frame_counter
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and #1
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cmp #0
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bne @end
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lda #0
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cmp player_vel_x
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beq @end ; If player_vel_x = 0, skip decay
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; If player_vel_x > 0, decrement
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bpl :+
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ldx player_vel_x
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dex
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stx player_vel_x
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jmp @end
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:
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; Else if player_vel_x < 0, increment
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ldx player_vel_x
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inx
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stx player_vel_x
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@end:
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; Jump
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jsr btn_a
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cmp #0
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beq @fail_jump ; If jump not pressed, forget it
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lda jump_pressed_last_frame
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cmp #1
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beq @fail_jump ; If jump last frame, forget it
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; Jump newly pressed this frame
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lda #250
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sta player_vel_y
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@fail_jump:
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jsr btn_a
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sta jump_pressed_last_frame
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; Gravity
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lda frame_counter
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and #1
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cmp #0
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bne :+
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lda player_vel_y
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clc
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adc #1 ; Add 2 to velocity
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sta player_vel_y
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:
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; Apply Y velocity
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lda player_pos_y
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clc
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adc player_vel_y
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sta player_pos_y
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; Keep grounded
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cmp #200
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bcc :+
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lda #0
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sta player_vel_y
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lda #200
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sta player_pos_y
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:
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; Bonk
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lda #8
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cmp player_pos_y
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bcc :+
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lda #0
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sta player_vel_y
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lda #8
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sta player_pos_y
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:
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; Apply X velocity
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lda player_pos_x
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clc
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adc player_vel_x
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sta player_pos_x
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|
|
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rts
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update_background:
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rts
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;lda $2002
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;lda #$20
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;sta $2006
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;lda #$00
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;sta $2006
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ldx #1
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ldy #1
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jsr ppu_update_tile
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lda #1
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sta $2007
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|
rts
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setup_background:
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lda $2002 ; reset latch
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lda #$20
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sta $2006
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lda #$00
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sta $2006
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; empty nametable
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lda #0
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ldy #30 ; 30 rows
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:
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ldx #32 ; 32 columns
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:
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sta $2007
|
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dex
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bne :-
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dey
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bne :--
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lda $2002
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lda #$20
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sta $2006
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lda #$00
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sta $2006
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ldy #0
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@row_start:
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ldx #0
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:
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txa
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pha
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|
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; index is (Y * 16) + X
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stx temp_x
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lda #16
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jsr mul_y
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clc
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adc temp_x
|
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tax
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lda level, X
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ldx #5
|
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jsr mul_x
|
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tax
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lda metatiles+0, X
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sta $2007
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|
lda metatiles+1, X
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|
sta $2007
|
|
|
|
pla
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tax
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|
inx
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cpx #16
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bne :-
|
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|
|
; again
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ldx #0
|
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:
|
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txa
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pha
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|
|
; index is (Y * 16) + X
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stx temp_x
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lda #16
|
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jsr mul_y
|
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clc
|
|
adc temp_x
|
|
tax
|
|
|
|
lda level, X
|
|
ldx #5
|
|
jsr mul_x
|
|
tax
|
|
|
|
lda metatiles+2, X
|
|
sta $2007
|
|
lda metatiles+3, X
|
|
sta $2007
|
|
|
|
pla
|
|
tax
|
|
inx
|
|
cpx #16
|
|
bne :-
|
|
iny
|
|
cpy #15
|
|
bne @row_start
|
|
|
|
|
|
; clear attributes
|
|
lda #0
|
|
ldx #64 ; 64 bytes
|
|
:
|
|
lda #%11100100
|
|
|
|
sta $2007
|
|
dex
|
|
bne :-
|
|
|
|
rts
|
|
|
|
|
|
|
|
lda $2002 ; reset latch
|
|
lda #$20
|
|
sta $2006
|
|
lda #$00
|
|
sta $2006
|
|
; empty nametable
|
|
lda #0
|
|
ldy #30 ; 30 rows
|
|
:
|
|
ldx #32 ; 32 columns
|
|
:
|
|
sta $2007
|
|
dex
|
|
bne :-
|
|
dey
|
|
bne :--
|
|
; set all attributes to 0
|
|
lda #0
|
|
ldx #64 ; 64 bytes
|
|
:
|
|
txa
|
|
and #%00000011
|
|
asl
|
|
asl
|
|
asl
|
|
asl
|
|
sta temp
|
|
txa
|
|
and #%00000011
|
|
ora temp
|
|
lda #0
|
|
|
|
sta $2007
|
|
dex
|
|
bne :-
|
|
|
|
|
|
|
|
|
|
|
|
; fill in an area in the middle with 1/2 checkerboard
|
|
lda #1
|
|
ldy #0 ; start at row 8
|
|
:
|
|
pha ; temporarily store A, it will be clobbered by ppu_address_tile routine
|
|
ldx #8 ; start at column 8
|
|
jsr ppu_address_tile
|
|
pla ; recover A
|
|
|
|
ldx #8
|
|
:
|
|
sta $2007
|
|
eor #$3
|
|
inx
|
|
cpx #(32-8)
|
|
bcc :-
|
|
eor #$3
|
|
iny
|
|
cpy #(30-8)
|
|
bcc :--
|
|
|
|
lda #$24
|
|
sta $2006
|
|
lda #$00
|
|
sta $2006
|
|
lda #$00
|
|
ldy #30
|
|
:
|
|
ldx #32
|
|
:
|
|
sta $2007
|
|
clc
|
|
adc #1
|
|
and #3
|
|
dex
|
|
bne :-
|
|
clc
|
|
adc #1
|
|
and #3
|
|
dey
|
|
bne :--
|
|
|
|
lda #0
|
|
ldy #4
|
|
:
|
|
ldx #16
|
|
:
|
|
sta $2007
|
|
dex
|
|
bne :-
|
|
|
|
clc
|
|
adc #%01010101
|
|
dey
|
|
bne :--
|
|
|
|
rts
|
|
|
|
mul_x:
|
|
cmp #0
|
|
beq @zero
|
|
cpx #0
|
|
beq @zero
|
|
|
|
sta temp_mul
|
|
|
|
txa
|
|
pha
|
|
lda #0
|
|
:
|
|
clc
|
|
adc temp_mul
|
|
dex
|
|
bne :-
|
|
sta temp_mul
|
|
pla
|
|
tax
|
|
lda temp_mul
|
|
rts
|
|
|
|
@zero:
|
|
lda #0
|
|
rts
|
|
|
|
mul_y:
|
|
cmp #0
|
|
beq @zero
|
|
cpy #0
|
|
beq @zero
|
|
|
|
sta temp_mul
|
|
|
|
tya
|
|
pha
|
|
lda #0
|
|
:
|
|
clc
|
|
adc temp_mul
|
|
dey
|
|
bne :-
|
|
sta temp_mul
|
|
pla
|
|
tay
|
|
lda temp_mul
|
|
rts
|
|
|
|
@zero:
|
|
lda #0
|
|
rts
|
|
|
|
controller:
|
|
lda #1
|
|
sta $4016
|
|
sta buttons
|
|
lda #0
|
|
sta $4016
|
|
:
|
|
lda $4016
|
|
lsr
|
|
rol buttons
|
|
bcc :-
|
|
|
|
rts
|
|
|
|
btn_right:
|
|
lda buttons
|
|
and #%00000001
|
|
rts
|
|
|
|
btn_left:
|
|
lda buttons
|
|
and #%00000010
|
|
lsr
|
|
rts
|
|
|
|
btn_down:
|
|
lda buttons
|
|
and #%00000100
|
|
lsr
|
|
lsr
|
|
rts
|
|
|
|
btn_up:
|
|
lda buttons
|
|
and #%00001000
|
|
lsr
|
|
lsr
|
|
lsr
|
|
rts
|
|
|
|
btn_start:
|
|
lda buttons
|
|
and #%00010000
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
rts
|
|
|
|
btn_select:
|
|
lda buttons
|
|
and #%00100000
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
rts
|
|
|
|
btn_b:
|
|
lda buttons
|
|
and #%01000000
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
rts
|
|
|
|
btn_a:
|
|
lda buttons
|
|
and #%10000000
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
lsr
|
|
rts
|
|
|