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update bg2 fix. #402

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Merged
blkerby merged 1 commit into from
Nov 4, 2026
Merged

update bg2 fix. #402

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Binary file modified patches/ips/vanilla_bugfixes.ips
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1 change: 0 additions & 1 deletion patches/rom_map/Bank 82.txt
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
[unused vanilla code]
8B18 - 8B1F: [free] [unused vanilla code] - 8 bytes
8D51 - 8DBC: [free] [vanilla bg2 code, patched out in vanilla_bugfixes] - 108 bytes
A3D9 - A424: [free] [unused vanilla code] - 76 bytes
B5E8 - B62A: [free] [unused vanilla code] - 67 bytes
B650 - B671: [free] [unused vanilla code] - 34 bytes
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2 changes: 1 addition & 1 deletion patches/rom_map/RAM.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ $7ED823: randomizer-specific event flags:
$0010: metal pirates room door unlocked
$7ED825: pause menu room name enabled (map_area.asm)
$7ed86c: bomb_torizo.asm
$7EDF5C-$7EEF5B: [FREE] (vanilla_bugfixes removes the BG2 backup that used this block of ram.)
$7EE01E-$7EEF5B: [FREE] (vanilla_bugfixes removes most of the BG2 backup that used this block of ram.)
$7EF4A0-$7EF4AF: temp storage for special tile (reserve_hud.asm)
$7EF4B0-$7EF4E0: backup of DMA registers in decompression.asm
$7EF4E0-$7EF4E4: pending MSU/SPC playback state (msu1.asm)
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43 changes: 32 additions & 11 deletions patches/src/vanilla_bugfixes.asm
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Expand Up @@ -252,19 +252,40 @@ assert pc() <= !bank_82_free_space_end

; Pause menu tiles routine DMA transfer size bug fix.
; Vanilla code transfers too many bytes, destroying the BG2 tilemap.
; Correcting the DMA transfer size means the backup/restore BG2 pause hook isn't needed.
; Which also frees up the 4k block of ram used for the backup / restore.
; Correcting the DMA transfer size means the full backup/restore isn't needed.
; The Typewriter text is written directly to VRAM so we backup just those rows instead.
; nn_357

;org $828ed2 ; Correct DMA transfer size $1000, [hud_expansion_opaque already fixes this, included for reference].
; db $10

org $828d08 ; Back up BG2 tilemap for pause menu
bra +
nop
+

org $829377 ; Restore BG2 tilemap from pause menu
bra +
nop
+
org $828D51 ;;; $8D51: Back up BG2 tilemap for pause menu (save typewrite text during pause) ;;;
BackupBG2Tilemap:
PHP
SEP #$20
LDA #$00 : STA $2116 ; VRAM $4900 (BG2 row 8)
LDA #$49 : STA $2117
REP #$20
LDA #$3981 : STA $4310 ; VRAM -> WRAM, reads $2139/$213A
LDA #$DF5C : STA $4312
LDA #$00C2 : STA $4315 ; 194 bytes: 2 junk (prefetch glitch) + 192 real (rows 8-Ah)
SEP #$20
LDA #$7E : STA $4314
LDA #$02 : STA $420B
PLP
RTS
assert pc() <= $828D96

org $828D96 ;;; $8D96: Restore BG2 tilemap from pause menu ;;;
RestoreBG2Tilemap:
PHP
SEP #$20
LDA #$00 : STA $2116
LDA #$49 : STA $2117
LDA #$80 : STA $2115
JSL $8091A9
db $01,$01,$18 : dl $7EDF5E : dw $00C0 ; skip the 2 junk bytes
LDA #$02 : STA $420B
PLP
RTS
assert pc() <= $828DBD
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