88 lines
2.3 KiB
NASM
88 lines
2.3 KiB
NASM
;**********
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; Memory
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;**********
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.segment "ZEROPAGE"
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; NMI Flags to activate graphical update
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; Note: You cannot activate all updates.
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; You need to have a execution time
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; < ~2273 cycles (2000 to be sure)
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; 7 bit 0
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; ---- ----
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; E..R PASB
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; | | ||||
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; | | |||+- Background tiles update
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; | | ||| Execution time depend on data
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; | | ||| (cycles ~= 16 + 38*p + for i:p do (14*p[i].n))
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; | | ||| (p=packet number, p[i].n = packet data size)
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; | | ||+-- Sprites update (513+ cycles)
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; | | |+--- Nametables attributes update (821 cycles)
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; | | +---- Palettes update (356 cycles)
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; | +------ Scroll update (31 cycles)
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; +--------- 1 when NMI has ended, should be set to 0 after reading.
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; If let to 1, it means the NMI is disable
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nmi_flags: .res 1
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.export _nmi_flags=nmi_flags
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; Scroll X position
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scroll_x: .res 1
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.export _scroll_x=scroll_x
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; Scroll Y position
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scroll_y: .res 1
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.export _scroll_y=scroll_y
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; Nametable high adress to update attributes for
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; $23 = Nametable 1
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; $27 = Nametable 2
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; $2B = Nametable 3
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; $2F = Nametable 4
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atr_nametable: .res 1
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.export _atr_nametable=atr_nametable
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; value of the PPU_MASK (need to be refresh manually)
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ppu_ctrl_val: .res 1
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.export _ppu_ctrl_val=ppu_ctrl_val
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; Attributes data to send to PPU during VBLANK
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attributes: .res 64
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.export _attributes=attributes
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; Palettes data to send to PPU during VBLANK
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; byte 0 = transparente color
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; byte 1-3 = background palette 1
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; byte 4-6 = background palette 2
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; ...
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; byte 13-16 = sprite palette 1
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; ...
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palettes: .res 25
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.export _palettes=palettes
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; Background data to send to PPU during VBLANK
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; Packet structure:
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; byte 0 = v.ssssss (v= vertical draw, s= size)
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; byte 1-2 = ppu adress
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; byte 3-s = tile data
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; packet of size 0 means there is no more data to draw
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background: .res 128
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.export _background=background
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;****************
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; OAM SEGMENT
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;****************
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.segment "OAM"
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OAM:
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.export _OAM=OAM
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;****************
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; BSS SEGMENT
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;****************
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.segment "BSS"
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game_state: .res 1
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.export _game_state=game_state
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