Guides:Coin Case ACE: Difference between revisions

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m (TimoVM moved page Guides:Coin Case ACE with stat experience redirection to Guides:Coin Case ACE: Misspelled title: Stat Experience is no longer involved in the setup)
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===Effect of the Coin Case===
===Effect of the Coin Case===


The effects of the Coin Case are described in more detail on the following [http://Coin%20Case%20glitches#cause wiki page]. Relevant to this setup is that the setup will redirect execution to address $FA98 (echo ram copy of $DA98), which is in the middle of party pokémon #3's stat experience data. During this redirection, the stack pointer gets incremented once and an address gets popped from the stack. The global effect is that the stack pointer is decremented once compared to when the Coin Case was used.
The effects of the Coin Case are described in more detail on the following [http://Coin%20Case%20glitches#cause wiki page]. Relevant to this setup is that the used movement pattern will redirect execution to address $EEEE (echo ram copy of $CEEE), which is the second character of the last read mail. During this redirection, the stack pointer gets incremented once and an address gets popped from the stack. The global effect is that the stack pointer is decremented once compared to when the Coin Case was used.

===Effect of party pokémon #3===

Defeating the provided list of pokémon will result in the following values at the following addresses, assuming the pokémon is in party slot #3:

<pre>
DA95 00 nop
DA96 75 ld [hl], l
DA97 00 nop
DA98 94 sub a, h
DA99 00 nop
DA9A C3
DA9B 00
DA9C CF jp $CF00
DA9D 00 nop
DA9E 6E ld l, [hl]
</pre>

Executing Coin Case at the location described in the setup will cause execution to jump to $DA98. It will then harmlessly slide through the sub a, h and nop instructions, after which execution will jump to $CF00, which is in the middle of the last buffered mail.


===Effect of the mail===
===Effect of the mail===
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<pre>
<pre>
80 add a, b
A7 and a ; Filler
⚫
A7 and a ; Reset carry flag
80 add a, b
D4 B9 F8 call nc, $F8B9 ; Box names start at $D8BF/F8BF, setting the active box to box 1 will ensure we can safely slide through.
80 add a, b
E1 pop hl ; Additional pop to clear return address of call to screen data
80 add a, b
D1 pop de ; Set de to $0075, which holds value $00. Ensures that print function will end immediately after resuming
80 add a, b
E8 FF add sp, -1 ; Fix the effect of increasing the stack pointer
80 add a, b
80 add a, b
F1 pop af ; a = $03
E0 9F ld ($FF9F), a ; Ensures return to ROM bank 3 after resuming execution
80 add a, b
A7 and a ; Reset carry flag. Not strictly necessary, but added for safety for now
80 add a, b
80 add a, b
D0 ret nc
80 add a, b
80 add a, b
80 add a, b
80 add a, b
80 add a, b
80 add a, b
4E ld c, (hl) ; Newline control character.
80 add a, b
80 add a, b
AF xor a ; Located at $CF00, all values before this address are filler and will not be executed.
D6 FD sub $FD ; Set a to $03.
E0 9F ld (hRomBank), a; Set current ROM bank to bank 3. This ROM bank contains item and pack data and ensures safe return.
E8 FF add sp, $FF ; $FF is interpreted as a singed integer, stack pointer gets decremented and the stack is now properly aligned again.
D1 pop de
D1 pop de
D1 pop de ; Pop text command related addresses so that returning from ACE execution will resume normal game operation.
⚫
AF xor a ; Set a to $00, set carry flag to 0.
D2 B9 F8 jp nc, $F8B9 ; Jump to echo ram copy of $D8B9, which lies a few bytes before box data.
</pre>
</pre>


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The code overwrites part of itself to call the byteFill function. This will fill the area between $D57E and $D5AF with $FF values, setting all 50 TM quantities to 255.
The code overwrites part of itself to call the byteFill function. This will fill the area between $D57E and $D5AF with $FF values, setting all 50 TM quantities to 255.


Separately, this code overwrites the latter half of party pokémon #5's stat experience data, allowing it to function as a TM25 bootstrap that redirects execution to the Mail Writer.
Separately, this code overwrites the latter half of party pokémon #3's stat experience data, allowing it to function as a TM25 bootstrap that redirects execution to the Mail Writer.


Lastly, the value of the first item ID in the main item pocket is overwritten so that it becomes a TM25.
Lastly, the value of the first item ID in the main item pocket is overwritten so that it becomes a TM25.
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Box 5: $D8E3
Box 5: $D8E3
E6 84 and $84 ; a = $04
E6 84 and $84 ; a = $04
EA FB FA ld ($FAFB), a
EA 9B FA ld ($FA9B), a
D6 86 sub $86 ; a = $7E
D6 86 sub $86 ; a = $7E
FB ei
FB ei
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Box 6: $D8EC
Box 6: $D8EC
EA F5 F8 ld ($F8F5), a
EA F5 F8 ld ($F8F5), a
EA FD FA ld ($FAFD), a
EA 9D FA ld ($FA9D), a
F6 FF or $FF ; a = $FF, reset carry flag
F6 FF or $FF ; a = $FF, reset carry flag
21
21
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Box 8: $D907
Box 8: $D907
E6 D2 and $D2 ; a = $D2
E6 D2 and $D2 ; a = $D2
EA FC FA ld ($FAFC), a
EA 9C FA ld ($FA9C), a
D6 FA sub $FA ; a = $D8, TM25's item ID
D6 FA sub $FA ; a = $D8, TM25's item ID
FB ei
FB ei
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EA B8 F5 ld (wItems), a ; Main item pocket, first item ID
EA B8 F5 ld (wItems), a ; Main item pocket, first item ID
D6 E3 sub $E3 ; a = $F5
D6 E3 sub $E3 ; a = $F5
EA FE FA ld ($FAFE), a
EA 9E FA ld ($FA9E), a
50 ld d, b
50 ld d, b


Box 10: $D919
Box 10: $D919
D6 B7 sub $B7 ; a = 3E, reset carry flag
D6 B7 sub $B7 ; a = 3E, reset carry flag
EA FA FA ld ($FAFA), a
EA 9A FA ld ($FA9A), a
D0 ret nc
D0 ret nc
50 ld d, b
50 ld d, b
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