This article has a talk page!This page contains notes for the game Family Computer Disk System.
3DS VC Nazo no Murasamejou/The Mysterious Murasame Castle#
Below is a disassembly of the modified FDS BIOS code in the 3DS Virtual Console release of The Mysterious Murasame Castle, which hijacks a subroutine at $EB13 (originally for reading the Family BASIC keyboard). The game itself appears to have been modified to call or jump to various entry points located in this section.
ReadKeyboard_Mod:
eb13 a5 83 lda $83
eb15 c9 08 cmp #$08
eb17 90 08 bcc leb21
eb19 ad 43 03 lda $0343
eb1c d0 03 bne leb21
eb1e a9 00 lda #$00
eb20 60 rts
eb21 a5 f5 leb21 lda $f5 ; P1 buttons
eb23 29 10 and #$10 ; start pressed?
eb25 60 rts
eb26 a2 22 leb26 ldx #$22
eb28 a5 51 lda $51
eb2a c9 03 cmp #$03
eb2c 90 02 bcc leb30
eb2e a2 ff ldx #$ff
eb30 8e d4 b5 leb30 stx $b5d4
eb33 4c e4 64 jmp $64e4
eb36 a9 3c leb36 lda #$3c
eb38 8d 0f 01 sta $010f
eb3b a9 14 lda #$14
eb3d 85 1a sta $1a
eb3f 60 rts
eb40 48 leb40 pha
eb41 ad 0f 01 lda $010f
eb44 c9 01 cmp #$01
eb46 90 03 bcc leb4b
eb48 ce 0f 01 dec $010f
eb4b 68 leb4b pla
eb4c 29 40 and #$40
eb4e f0 05 beq leb55
eb50 b0 03 bcs leb55
eb52 4c 16 6f jmp $6f16
eb55 4c 79 6f leb55 jmp $6f79
; end of patch, rest of ReadKeyboard follows
eb58 ff ??? ; eor #$ff operand
eb59 95 00 sta $00,x
eb5b ca dex
eb5c 10 c8 bpl leb26
eb5e a4 fb ldy $fb
eb60 09 ff ora #$ff
eb62 8c 16 40 sty $4016
eb65 60 rts(Source: TakuikaNinja)