iigs-game-engine/demos/smb/ppu.s
2023-06-11 12:00:52 -05:00

1552 lines
37 KiB
ArmAsm

; PPU simulator
;
; Any read/write to the PPU registers in the ROM is intercepted and passed here.
const8 mac
db ]1,]1,]1,]1,]1,]1,]1,]1
<<<
const32 mac
const8 ]1
const8 ]1+1
const8 ]1+2
const8 ]1+3
<<<
rep8 mac
db ]1
db ]1
db ]1
db ]1
db ]1
db ]1
db ]1
db ]1
<<<
mx %11
dw $a5a5 ; marker to find in memory
ppuaddr ENT
ds 2 ; 16-bit ppu address
w_bit dw 1 ; currently writing to high or low to the address latch
vram_buff dw 0 ; latched data when reading VRAM ($0000 - $3EFF)
ppuincr dw 1 ; 1 or 32 depending on bit 2 of PPUCTRL
spadr dw $0000 ; Sprite pattern table ($0000 or $1000) depending on bit 3 of PPUCTRL
ntaddr dw $2000 ; Base nametable address ($2000, $2400, $2800, $2C00), bits 0 and 1 of PPUCTRL
bgadr dw $0000 ; Background pattern table address
ppuctrl dw 0 ; Copy of the ppu ctrl byte
ppumask dw 0 ; Copy of the ppu mask byte
ppustatus dw 0
oamaddr dw 0 ; Typically this will always be 0
ppuscroll dw 0 ; Y X coordinates
ntbase db $20,$24,$28,$2c
assert_lt mac
cmp ]1
bcc ok
brk ]2
ok
<<<
assert_x_lt mac
cpx ]1
bcc ok
brk ]2
ok
<<<
cond mac
bit ]1
beq cond_0
lda ]3
bra cond_s
cond_0 lda ]2
cond_s sta ]4
<<<
; $2000 - PPUCTRL (Write only)
PPUCTRL_WRITE ENT
php
phb
phk
plb
sta ppuctrl
phx
; Set the pattern table base address
and #$03
tax
lda ntbase,x
sta ntaddr+1
; Set the vram increment
lda ppuctrl
cond #$04;#$01;#$20;ppuincr
; Set the sprite table address
lda ppuctrl
cond #$08;#$00;#$10;spadr+1
; Set the background table address
lda ppuctrl
cond #$10;#$00;#$10;bgadr+1
plx
lda ppuctrl
plb
plp
rtl
; $2001 - PPUMASK (Write only)
PPUMASK_WRITE ENT
stal ppumask
rtl
; $2002 - PPUSTATUS For "ldx ppustatus"
PPUSTATUS_READ_X ENT
php
pha
lda #1
stal w_bit ; Reset the address latch used by PPUSCROLL and PPUADDR
ldal ppustatus
tax
and #$7F ; Clear the VBL flag
stal ppustatus
pla ; Restore the accumulator (return value in X)
plp
phx ; re-read x to set any relevant flags
plx
rtl
PPUSTATUS_READ ENT
php
lda #1
stal w_bit ; Reset the address latch used by PPUSCROLL and PPUADDR
ldal ppustatus
pha
and #$7F ; Clear the VBL flag
stal ppustatus
pla ; pop the return value
plp
pha ; re-read accumulator to set any relevant flags
pla
rtl
; $2003
OAMADDR_WRITE ENT
stal oamaddr
rtl
; $2005 - PPU SCROLL
PPUSCROLL_WRITE ENT
php
phb
phk
plb
phx
pha
ldx w_bit
sta ppuscroll,x
txa
eor #$01
sta w_bit
pla
plx
plb
plp
rtl
; $2006 - PPUADDR
PPUADDR_WRITE ENT
php
phb
phk
plb
phx
pha
ldx w_bit
sta ppuaddr,x
; assert_lt #$40;$D0
txa
eor #$01
sta w_bit
lda ppuaddr+1 ; Stay within the mirrored memory space
and #$3F
sta ppuaddr+1
pla
plx
plb
plp
rtl
; 2007 - PPUDATA (Read/Write)
;
; If reading from the $0000 - $3EFF range, the value from vram_buff is returned and the actual data is loaded
; post-fetch.
PPUDATA_READ ENT
php
phb
phk
plb
phx
rep #$30 ; do a 16-bit update of the address
ldx ppuaddr
txa
; assert_lt #$4000;$d1
clc
adc ppuincr
and #$3FFF
sta ppuaddr
sep #$20 ; back to 8-bit acc for the read itself
cpx #$3F00 ; check which range of memory we are accessing?
bcc :buff_read
lda PPU_MEM,x
bra :out
:buff_read
lda vram_buff ; read from the buffer
pha
lda PPU_MEM,x ; put the data in the buffer for the next read
sta vram_buff
pla ; pop the return value
:out
sep #$10
plx
plb
plp
pha
pla
rtl
ppu_write_log_len dw 0
ppu_write_log ds 100 ; record the first 50 PPU write addresses in each frame
nt_queue_front dw 0
nt_queue_end dw 0
nt_queue ds 2*{NT_QUEUE_SIZE}
PPUDATA_WRITE ENT
php
phb
phk
plb
pha
phx
phy
rep #$10
ldx ppuaddr
cmp PPU_MEM,x
beq :nochange
ldy PPU_MEM,x ; Save in case we need to compare later
sta PPU_MEM,x
rep #$30
txa
clc
adc ppuincr
and #$3FFF
sta ppuaddr
; Anything between $2000 and $3000, we need to add to the queue. We can't reject updates here because we may not
; actually update the GTE tile store for several game frames and the position of the tile within the tile store
; may change if the screen is scrolling
;
; There is one special case. We want the nt_queue to only be a queue of tiles to possibly redraw. If the PPU
; data that is updated is in the attribute table area, then we do some extra work to decide which of the 16
; tiles *actually* need to be redrawn
cpx #$3000
bcs :nocache
cpx #$2000 ; Change to $2080 to ignore score field updates
bcc :nocache
txa
and #$03C0
cmp #$03C0
beq :attrtbl
jsr :enqueue ; Add the address in the X register to the queue
:nocache
cpx #$3F00
bcc :done
brl :extra
; bcs :extra
; bra :done
:nochange
rep #$30
txa
clc
adc ppuincr
and #$3FFF
sta ppuaddr
:done
sep #$30
ply
plx
pla
plb
plp
rtl
mx %00
:enqueue
lda nt_queue_end
tay
inc
inc
and #NT_QUEUE_MOD
cmp nt_queue_front
beq :full
sta nt_queue_end
txa
sta nt_queue,y
:full
; lda #1
; jsr setborder
rts
:attrtbl
txa ; Calculate the base address in the nametable from the attribute address
and #$2C00
pha
txa
and #$0007
asl
asl
ora 1,s
sta 1,s
txa
and #$0038
asl
asl
asl
asl
ora 1,s
sta 1,s
tya
eor PPU_MEM,x ; Identify bits that have changed
and #$00FF
bit #$00C0
beq :skip_bot_right
pha
lda 3,s
clc
adc #64+2 ; offset 2 rows an 2 columns
tax
jsr :enqueue_blk
pla
:skip_bot_right
bit #$0030
beq :skip_bot_left
pha
lda 3,s
clc
adc #64 ; offset 2 rows
tax
jsr :enqueue_blk
pla
:skip_bot_left
bit #$000C
beq :skip_top_right
pha
lda 3,s
tax
inx
inx
tax
jsr :enqueue_blk
pla
:skip_top_right
bit #$0003
beq :skip_top_left
lda 1,s
tax
jsr :enqueue_blk
:skip_top_left
pla ; pop the base address off
brl :done
; Pass in PPU address in X register
:enqueue_blk
jsr :enqueue
inx
jsr :enqueue
txa
clc
adc #32
tax
jsr :enqueue
dex
jmp :enqueue
setborder
php
sep #$20
eorl $E0C034
and #$0F
eorl $E0C034
stal $E0C034
plp
rts
; Do some extra work to keep palette data in sync
;
; Based on the palette data that SMB uses, we remap the NES palette entries
; based on the AreaType, so most of the PPU writes are ignored. However,
; we do update some specific palette entries
;
; BG0,0 maps to IIgs Palette index 0 (Background color)
; BG3,1 maps to IIgs Palette index 1 (Color cycle for blocks)
; SP0,1 maps to IIgs Palette index 14 (Player primary color; changes with fire flower)
; SP0,3 maps to IIgs Palette index 15 (Player primary color; changes with fire flower)
mx %00
:extra
txa
and #$001F
asl
tax
jmp (palTbl,x)
palTbl dw ppu_3F00,ppu_3F01,ppu_3F02,ppu_3F03
dw ppu_3F04,ppu_3F05,ppu_3F06,ppu_3F07
dw ppu_3F08,ppu_3F09,ppu_3F0A,ppu_3F0B
dw ppu_3F0C,ppu_3F0D,ppu_3F0E,ppu_3F0F
dw ppu_3F10,ppu_3F11,ppu_3F12,ppu_3F13
dw ppu_3F14,ppu_3F15,ppu_3F16,ppu_3F17
dw ppu_3F18,ppu_3F19,ppu_3F1A,ppu_3F1B
dw ppu_3F1C,ppu_3F1D,ppu_3F1E,ppu_3F1F
; Background color
ppu_3F00
lda PPU_MEM+$3F00
ldx #0
brl extra_out
; Shadow for background color
ppu_3F10
lda PPU_MEM+$3F10
ldx #0
brl extra_out
; Tile palette 3, color 1
ppu_3F0D
lda PPU_MEM+$3F0D
ldx #2
brl extra_out
; Sprite Palette 0, color 1
ppu_3F11
lda PPU_MEM+$3F11
ldx #28
brl extra_out
ppu_3F13
lda PPU_MEM+$3F13
ldx #30
brl extra_out
ppu_3F01
ppu_3F02
ppu_3F03
ppu_3F04
ppu_3F05
ppu_3F06
ppu_3F07
ppu_3F08
ppu_3F09
ppu_3F0A
ppu_3F0B
ppu_3F0C
ppu_3F0E
ppu_3F0F
ppu_3F12
ppu_3F14
; Allow the second sprite palette to set set by the ROM in world 4 because it switched to the bowser
; palette when player reaches the end of the level. Mapped to IIgs palette indices 8, 9, 10
CASTLE_AREA_TYPE equ 3
ppu_3F15
lda LastAreaType
cmp #CASTLE_AREA_TYPE
bne no_pal
lda PPU_MEM+$3F15
ldx #8*2
brl extra_out
ppu_3F16
lda LastAreaType
cmp #CASTLE_AREA_TYPE
bne no_pal
lda PPU_MEM+$3F16
ldx #9*2
brl extra_out
ppu_3F17
lda LastAreaType
cmp #CASTLE_AREA_TYPE
bne no_pal
lda PPU_MEM+$3F17
ldx #10*2
brl extra_out
ppu_3F18
ppu_3F19
ppu_3F1A
ppu_3F1B
ppu_3F1C
ppu_3F1D
ppu_3F1E
ppu_3F1F
brl no_pal
; Exit code to set a IIgs palette entry from the PPU memory
;
; A = NES palette value
; X = IIgs Palette index
extra_out
and #$00FF
asl
tay
lda nesPalette,y
stal $E19E00,x
no_pal
sep #$30
ply
plx
pla
plb
plp
rtl
; Trigger a copy from a page of memory to OAM. Since this is a DMA operation, we can cheat and do a 16-bit copy
PPUDMA_WRITE ENT
php
phb
phk
plb
phx
pha
rep #$30
xba
and #$FF00
tax
]n equ 0
lup 128
ldal ROMBase+]n,x
sta PPU_OAM+]n
]n = ]n+2
--^
sep #$30
pla
plx
plb
plp
rtl
y_offset_rows equ 2
y_height_rows equ 25
y_offset equ {y_offset_rows*8}
y_height equ {y_height_rows*8}
max_nes_y equ {y_height+y_offset-8}
x_offset equ 16
; Scan the OAM memory and copy the values of the sprites that need to be drawn. There are two reasons to do this
;
; 1. Freeze the OAM memory at this instanct so that the NES ISR can keep running without changing values
; 2. We have to scan this list twice -- once to build up the shadow list and once to actually render the sprites
OAM_COPY ds 256
spriteCount ds 0
db 0 ; Pad in case we can to access using 16-bit instructions
mx %00
scanOAMSprites
stz Tmp5
sep #$30
ldx #4 ; Always skip sprite 0
ldy #0
:loop
lda PPU_OAM,x ; Y-coordinate
cmp #max_nes_y+1 ; Skip anything that is beyond this lint
bcs :skip
cmp #y_offset
bcc :skip
lda PPU_OAM+1,x ; $FC is an empty tile, don't draw it
cmp #$FC
beq :skip
lda PPU_OAM+3,x ; If X-coordinate is off the edge skip it, too.
cmp #255-8
bcs :skip
rep #$20
lda PPU_OAM,x
sta OAM_COPY,y
lda PPU_OAM+2,x
sta OAM_COPY+2,y
sep #$20
jsr debug_values
iny
iny
iny
iny
:skip
inx
inx
inx
inx
bne :loop
sty spriteCount ; Count * 4
rep #$30
rts
debug_values
; Debug APU values
phy
phx
rep #$30
ldx #0
ldy #$FFFF
lda APU_STATUS
and #$00FF
jsr DrawWord
ldx #8*160
ldy #$EEEE
lda APU_PULSE1_REG1
jsr DrawWord
ldx #16*160
ldy #$EEEE
lda APU_PULSE1_REG3
jsr DrawWord
ldx #24*160
ldy #$DDDD
lda APU_PULSE2_REG1
jsr DrawWord
ldx #32*160
ldy #$DDDD
lda APU_PULSE2_REG3
jsr DrawWord
ldx #40*160
ldy #$BBBB
lda APU_TRIANGLE_REG1
jsr DrawWord
ldx #48*160
ldy #$BBBB
lda APU_TRIANGLE_REG3
jsr DrawWord
; Fetch the ensoniq parameters
sep #$20
ldal irq_volume
stal $e1c000+sound_control ; access registers
lda #$80+pulse1_oscillator ; oscillator address
stal $e1c000+sound_address
ldal $e1c000+sound_data
ldal $e1c000+sound_data
xba
lda #$40+pulse1_oscillator ; oscillator volume
stal $e1c000+sound_address
ldal $e1c000+sound_data
ldal $e1c000+sound_data
rep #$30
ldx #{8*160}+{160-16}
ldy #$EEEE
jsr DrawWord
sep #$20
lda #$20+pulse1_oscillator ; oscillator freq high
stal $e1c000+sound_address
ldal $e1c000+sound_data
ldal $e1c000+sound_data
xba
lda #$00+pulse1_oscillator ; oscillator freq low
stal $e1c000+sound_address
ldal $e1c000+sound_data
ldal $e1c000+sound_data
rep #$30
ldx #{16*160}+{160-16}
ldy #$EEEE
jsr DrawWord
sep #$30
plx
ply
rts
; Screen is 200 lines tall. It's worth it be exact when building the list because one extra
; draw + shadow sequence takes at least 1,000 cycles.
shadowBitmap ds 32 ; Provide enough space for the full ppu range (240 lines) + 16 since the y coordinate can be off-screen
; A representation of the list as [top, bot) pairs
shadowListCount dw 0 ; Pad for 16-bit comparisons
shadowListTop ds 64
shadowListBot ds 64
mx %00
buildShadowBitmap
; zero out the bitmap (16-bit writes)
]n equ 0
lup 15
stz shadowBitmap+]n
]n = ]n+2
--^
; Run through the list of visible sprites and ORA in the bits that represent them
sep #$30
ldx #0
cpx spriteCount
beq :exit
:loop
phx
; ldy PPU_OAM,x
ldy OAM_COPY,x
cpy #max_nes_y ; Don't increment something right on the edge (allows )
; iny ; This is the y-coordinate of the top of the sprite
ldx y2idx,y ; Get the index into the shadowBitmap array for this y coordinate (y -> blk_y)
lda y2low,y ; Get the bit pattern for the first byte
ora shadowBitmap,x
sta shadowBitmap,x
lda y2high,y ; Get the bit pattern for the second byte
ora shadowBitmap+1,x
sta shadowBitmap+1,x
plx
inx
inx
inx
inx
cpx spriteCount
bcc :loop
:exit
rep #$30
rts
; Set the SCB values equal to the bitmap to visually debug
ldx #0
ldy #0
:vloop
lda #8
sta Tmp6
lda shadowBitmap+2,y
:iloop
asl
pha
lda #0
bcc :zero
inc
:zero stal $E19D00,x
pla
inx
dec Tmp6
bne :iloop
iny
cpy #25
bcc :vloop
rep #$30
rts
y2idx const32 $00
const32 $04
const32 $08
const32 $0C ; 128 bytes
const32 $10
const32 $14
const32 $18
const32 $1C
; Repeating pattern of 8 consecutive 1 bits
y2low rep8 $FF,$7F,$3F,$1F,$0F,$07,$03,$01
rep8 $FF,$7F,$3F,$1F,$0F,$07,$03,$01
rep8 $FF,$7F,$3F,$1F,$0F,$07,$03,$01
rep8 $FF,$7F,$3F,$1F,$0F,$07,$03,$01
y2high rep8 $00,$80,$C0,$E0,$F0,$F8,$FC,$FE
rep8 $00,$80,$C0,$E0,$F0,$F8,$FC,$FE
rep8 $00,$80,$C0,$E0,$F0,$F8,$FC,$FE
rep8 $00,$80,$C0,$E0,$F0,$F8,$FC,$FE
; 25 entries to multiple steps in the shadow bitmap to scanlines
mul8 db $00,$08,$10,$18,$20,$28,$30,$38
db $40,$48,$50,$58,$60,$68,$70,$78
db $80,$88,$90,$98,$A0,$A8,$B0,$B8
db $C0,$C8,$D0,$D8,$E0,$E8,$F0,$F8
; Given a bit pattern, create a LUT that count to the first set bit (MSB -> LSB), e.g. $0F = 4, $3F = 2
offset
db 8,7,6,6,5,5,5,5,4,4,4,4,4,4,4,4,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3
db 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
db 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
db 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
invOffset
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
db 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
db 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
db 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2
db 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,6,6,7,8
; Mask off all of the high 1 bits, keep all of the low bits after the first zero, e.g.
; offsetMask($E3) = offsetMask(11100011) = $1F. %11100011 & $1F = $03
offsetMask
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF
db $FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF,$FF ; 127 (everything here has a 0 in the high bit)
db $7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F ; $80 - $8F
db $7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F ; $90 - $9F
db $7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F ; $A0 - $AF
db $7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F,$7F ; $B0 - $BF
db $3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F ; $C0 - $CF
db $3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F,$3F ; $D0 - $DF
db $1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F,$1F ; $E0 - $EF
db $0F,$0F,$0F,$0F,$0F,$0F,$0F,$0F,$07,$07,$07,$07,$03,$03,$01,$00 ; $F0 - $FF
; Scan the bitmap list and call BltRange on the ranges
mx %00
drawShadowList
ldx #0
cpx shadowListCount
beq :exit
:loop
phx
lda shadowListBot,x
and #$00FF
tay
; cpy #201
; bcc *+4
; brk $cc
lda shadowListTop,x
and #$00FF
tax
; cpx #200
; bcc *+4
; brk $dd
lda #0 ; Invoke the BltRange function
jsl LngJmp
plx
inx
cpx shadowListCount
bcc :loop
:exit
rts
; Altername between BltRange and PEISlam to expose the screen
exposeShadowList
:last equ Tmp0
:top equ Tmp1
:bottom equ Tmp2
ldx #0
stx :last
cpx shadowListCount
beq :exit
:loop
phx
lda shadowListTop,x
and #$00FF
sta :top
cmp #200
bcc *+4
brk $44
lda shadowListBot,x
and #$00FF
sta :bottom
cmp #201
bcc *+4
brk $66
cmp :top
bcs *+4
brk $55
ldx :last
ldy :top
lda #0
jsl LngJmp ; Draw the background up to this range
ldx :top
ldy :bottom
sty :last ; This is where we ended
lda #1
jsl LngJmp ; Expose the already-drawn sprites
plx
inx
cpx shadowListCount
bcc :loop
:exit
ldx :last ; Expose the final part
ldy #y_height
lda #0
jsl LngJmp
rts
; This routine needs to adjust the y-coordinates based of the offset of the GTE playfield within
; the PPU RAM
shadowBitmapToList
:top equ Tmp0
:bottom equ Tmp2
:bitfield equ Tmp4
sep #$30
ldx #y_offset_rows ; Start at he third row (y_offset = 16) walk the bitmap for 25 bytes (200 lines of height)
lda #0
sta shadowListCount ; zero out the shadow list count
; This loop is called when we are not tracking a sprite range
:zero_loop
ldy shadowBitmap,x
beq :zero_next
lda {mul8-y_offset_rows},x ; This is the scanline we're on (offset by the starting byte)
clc
adc offset,y ; This is the first line defined by the bit pattern
sta :top
bra :one_next
:zero_next
inx
cpx #y_height_rows+y_offset_rows+1 ; End at byte 27
bcc :zero_loop
bra :exit ; ended while not tracking a sprite, so exit the function
:one_loop
lda shadowBitmap,x ; if the next byte is all sprite, just continue
cmp #$FF
beq :one_next
; The byte has to look like 1...10...0*. The first step is to mask off the high bits and store the result
; back into the shadowBitmap
tay
and offsetMask,y
sta shadowBitmap,x
lda {mul8-y_offset_rows},x
clc
adc invOffset,y
ldy shadowListCount
sta shadowListBot,y
lda :top
sta shadowListTop,y
iny
sty shadowListCount
; Loop back to check if there is more sprite data on this byte
bra :zero_loop
:one_next
inx
cpx #y_height_rows+y_offset_rows+1
bcc :one_loop
; If we end while tracking a sprite, add to the list as the last item
ldx shadowListCount
lda :top
sta shadowListTop,x
lda #y_height
sta shadowListBot,x
inx
stx shadowListCount
:exit
rep #$30
lda shadowListCount
cmp #64
bcc *+4
brk $13
rts
; Helper to bounce into the function in the FTblPtr. See IIgs TN #90
LngJmp
sty FTblTmp
asl
asl
tay
iny
lda [FTblPtr],y
pha
dey
lda [FTblPtr],y
dec
phb
sta 1,s
ldy FTblTmp ; Restore the y register
rtl
; Callback entrypoint from the GTE renderer
drawOAMSprites
phb
phd
phk
plb
pha ; Save the phase indicator
tdc ; Keep a copy of the second page of GTE direct page space
clc
adc #$0100
sta GTE_DP2+1
lda DPSave
tcd
; Save the pointer to the function table
sty FTblPtr
stx FTblPtr+2
pla
; Check what phase we're in
;
; Phase 1: A = 0
; Phase 2: A = 1
cmp #0
bne :phase2
; This is phase 1. We will build the sprite list and draw the background in the areas covered by
; sprites. This phase draws the sprites, too
; We need to "freeze" the OAM values, otherwise they can change between when we build the rendering pipeline
sei
ldal nmiCount
pha
jsr scanOAMSprites ; Filter out any sprites that don't need to be drawn
pla
cmpl nmiCount
beq *+4
brk $1F ; Should not have serviced the VBL interrupt here....
cli
jsr buildShadowBitmap ; Run though and quickly create a bitmap of lines with sprites
jsr shadowBitmapToList ; Scan the bitmap and create (top, bottom) pairs of ranges
jsr drawShadowList ; Draw the background lines that have sprite on them
jsr drawSprites ; Draw the sprites on top of the lines they occupy
bra :exit
; In Phase 2 we scan the shadow list and alternately blit the background in empty areas and
; PEI slam the sprite regions
:phase2
jsr exposeShadowList ; Show everything on the SHR screen
; Return form the callback
:exit
pld
plb
rtl
drawSprites
:tmp equ Tmp0
sep #$30 ; 8-bit cpu
; Run through the copy of the OAM memory
ldx #0
cpx spriteCount
bne oam_loop
rep #$30
rts
mx %11
oam_loop
phx ; Save x
lda OAM_COPY,x ; Y-coordinate
; inc ; Compensate for PPU delayed scanline
rep #$30
and #$00FF
asl
asl
asl
asl
asl
sta :tmp
asl
asl
clc
adc :tmp
clc
adc #$2000-{y_offset*160}+x_offset
sta :tmp
lda OAM_COPY+3,x
lsr
and #$007F
clc
adc :tmp
tay
lda OAM_COPY+2,x
pha
bit #$0040 ; horizontal flip
bne :hflip
lda OAM_COPY,x ; Load the tile index into the high byte (x256)
and #$FF00
lsr ; multiple by 128
tax
bra :noflip
:hflip
lda OAM_COPY,x ; Load the tile index into the high byte (x256)
and #$FF00
lsr ; multiple by 128
adc #64 ; horizontal flip
tax
:noflip
pla
asl
and #$0146 ; Set the vflip bit, priority, and palette select bits
phd
GTE_DP2 pea $0000
pld
jsr drawTileToScreen
pld
;drawTilePatch
; jsl $000000 ; Draw the tile on the graphics screen
sep #$30
plx ; Restore the counter
inx
inx
inx
inx
cpx spriteCount
bcc oam_loop
rep #$30
rts
; Custom tile blitter
;
; D = GTE blitter direct page space
; X = offset to the tile record
;
mx %00
; Temporary tile space on the direct page
tmp_tile_data equ 80
DP2_TILEDATA_AND_BANK01_BANKS equ 172
;USER_TILE_RECORD equ 178
USER_TILE_ID equ 178 ; copy of the tile id in the tile store
;USER_TILE_CODE_PTR equ 180 ; pointer to the code bank in which to patch
USER_TILE_ADDR equ 184 ; address in the tile data bank (set on entry)
USER_FREE_SPACE equ 186 ; a few bytes of scratch space
USER_SCREEN_ADDR equ 190
USER_TEMP_0 equ 192
USER_TEMP_1 equ 194
LDA_IND_LONG_IDX equ $B7
ORA_IND_LONG_IDX equ $17
SHR_LINE_WIDTH equ 160
; Draw a tile to the graphics screen
;
; D = GTE Page 2
; X = tile address
; Y = screen address
; A = tile control bits; h ($0100), v ($0040) and palette select ($0006)
jne mac
beq *+5
jmp ]1
<<<
jeq mac
bne *+5
jmp ]1
<<<
drawTileToScreen
stx USER_TILE_ADDR
sty USER_SCREEN_ADDR
phb
pei DP2_TILEDATA_AND_BANK01_BANKS
plb
pha
and #$0006 ; Isolate the palette selection bits
clc
adc #$0008 ; Sprite palettes are in the second half
xba
clc
adcl SwizzlePtr
sta USER_FREE_SPACE
lda #^AT1_T0 ; Bank is a constant
sta USER_FREE_SPACE+2 ; Set the pointer to the right swizzle table
pla
bit #$0040
beq :no_prio
bit #$0100
jeq :drawPriorityToScreen
; jmp :drawPriorityToScreenV
:no_prio
bit #$0100
jne :drawTileToScreenV
]line equ 0
lup 8
ldx USER_TILE_ADDR
ldy: {]line*4}+2,x ; Load the tile data lookup value
lda: {]line*4}+32+2,x ; Load the mask value
ldx USER_SCREEN_ADDR
andl $010000+{]line*SHR_LINE_WIDTH}+2,x ; Mask against the screen
db ORA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
stal $010000+{]line*SHR_LINE_WIDTH}+2,x
ldx USER_TILE_ADDR
ldy: {]line*4},x ; Load the tile data lookup value
lda: {]line*4}+32,x ; Load the mask value
ldx USER_SCREEN_ADDR
andl $010000+{]line*SHR_LINE_WIDTH},x ; Mask against the screen
db ORA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
stal $010000+{]line*SHR_LINE_WIDTH},x
]line equ ]line+1
--^
plb
plb ; Restore initial data bank
rts
:drawTileToScreenV
]line equ 0
lup 8
ldx USER_TILE_ADDR
ldy: {]line*4}+2,x ; Load the tile data lookup value
lda: {]line*4}+32+2,x ; Load the mask value
ldx USER_SCREEN_ADDR
andl $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x ; Mask against the screen
db ORA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
stal $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x
ldx USER_TILE_ADDR
ldy: {]line*4},x ; Load the tile data lookup value
lda: {]line*4}+32,x ; Load the mask value
ldx USER_SCREEN_ADDR
andl $010000+{{7-]line}*SHR_LINE_WIDTH},x ; Mask against the screen
db ORA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
stal $010000+{{7-]line}*SHR_LINE_WIDTH},x
]line equ ]line+1
--^
plb
plb ; Restore initial data bank
rts
:drawPriorityToScreen
]line equ 0
lup 8
ldx USER_TILE_ADDR
lda: {]line*4}+32+2,x ; Save the inverted mask
eor #$FFFF
sta USER_TEMP_1
ldy: {]line*4}+2,x ; Load the tile data lookup value
db LDA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
ldx USER_SCREEN_ADDR
eorl $010000+{]line*SHR_LINE_WIDTH}+2,x
sta USER_TEMP_0
; Convert the screen data to a mask. Zero in screen = zero in mask, else $F
ldal $010000+{]line*SHR_LINE_WIDTH}+2,x
bit #$F000
beq *+5
ora #$F000
bit #$0F00
beq *+5
ora #$0F00
bit #$00F0
beq *+5
ora #$00F0
bit #$000F
beq *+5
ora #$000F
eor #$FFFF
and USER_TEMP_0
and USER_TEMP_1
eorl $010000+{]line*SHR_LINE_WIDTH}+2,x
stal $010000+{]line*SHR_LINE_WIDTH}+2,x
ldx USER_TILE_ADDR
lda: {]line*4}+32,x ; Save the inverted mask
eor #$FFFF
sta USER_TEMP_1
ldy: {]line*4},x ; Load the tile data lookup value
db LDA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
ldx USER_SCREEN_ADDR
eorl $010000+{]line*SHR_LINE_WIDTH},x
sta USER_TEMP_0
ldal $010000+{]line*SHR_LINE_WIDTH},x
bit #$F000
beq *+5
ora #$F000
bit #$0F00
beq *+5
ora #$0F00
bit #$00F0
beq *+5
ora #$00F0
bit #$000F
beq *+5
ora #$000F
eor #$FFFF
and USER_TEMP_0
and USER_TEMP_1
eorl $010000+{]line*SHR_LINE_WIDTH},x
stal $010000+{]line*SHR_LINE_WIDTH},x
]line equ ]line+1
--^
plb
plb ; Restore initial data bank
rts
:drawPriorityToScreenV
]line equ 0
lup 8
ldx USER_TILE_ADDR
lda: {]line*4}+32+2,x ; Save the inverted mask
eor #$FFFF
sta USER_TEMP_1
ldy: {]line*4}+2,x ; Load the tile data lookup value
db LDA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
ldx USER_SCREEN_ADDR
eorl $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x
sta USER_TEMP_0
; Convert the screen data to a mask. Zero in screen = zero in mask, else $F
ldal $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x
bit #$F000
beq *+5
ora #$F000
bit #$0F00
beq *+5
ora #$0F00
bit #$00F0
beq *+5
ora #$00F0
bit #$000F
beq *+5
ora #$000F
eor #$FFFF
and USER_TEMP_0
and USER_TEMP_1
eorl $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x
stal $010000+{{7-]line}*SHR_LINE_WIDTH}+2,x
ldx USER_TILE_ADDR
lda: {]line*4}+32,x ; Save the inverted mask
eor #$FFFF
sta USER_TEMP_1
ldy: {]line*4},x ; Load the tile data lookup value
db LDA_IND_LONG_IDX,USER_FREE_SPACE ; Insert the actual tile data
ldx USER_SCREEN_ADDR
eorl $010000+{{7-]line}*SHR_LINE_WIDTH},x
sta USER_TEMP_0
ldal $010000+{{7-]line}*SHR_LINE_WIDTH},x
bit #$F000
beq *+5
ora #$F000
bit #$0F00
beq *+5
ora #$0F00
bit #$00F0
beq *+5
ora #$00F0
bit #$000F
beq *+5
ora #$000F
eor #$FFFF
and USER_TEMP_0
and USER_TEMP_1
eorl $010000+{{7-]line}*SHR_LINE_WIDTH},x
stal $010000+{{7-]line}*SHR_LINE_WIDTH},x
]line equ ]line+1
--^
plb
plb ; Restore initial data bank
rts
; Assume that when the tile is updated, it includes a full 10-bit value with the
; palette bits included with the lookup bits
NESTileBlitter
lda USER_TILE_ID
and #$0600 ; Select the tile palette from the tile id
clc
adcl SwizzlePtr
sta USER_FREE_SPACE
lda #^AT1_T0
sta USER_FREE_SPACE+2
ldx USER_TILE_ADDR ; Get the address of the tile (base only)
]line equ 0
lup 8
ldy: {]line*4},x
db LDA_IND_LONG_IDX,USER_FREE_SPACE
sta tmp_tile_data+{]line*4}
ldy: {]line*4}+2,x
db LDA_IND_LONG_IDX,USER_FREE_SPACE
sta tmp_tile_data+{]line*4}+2
]line equ ]line+1
--^
lda #1 ; Request tmp_tile_data be copied to tile store
rtl