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Generation II Glitch Discussion

Pokégear map glitch (Gold/Silver/Crystal) - Page 1

Pokégear map glitch (Gold/Silver/Crystal)

Posted by: Torchickens
Date: 2018-03-22 23:05:52
SatoMew found this and shared it with me on Discord. It works in both English Gold and English Crystal and likely most if not all other versions (I think SatoMew may have researched it for one of the Japanese versions first but I'm not entirely sure). Today I decided to research it a little. Note you need the Pokégear map from the guide in Cherrygrove City before doing this.

What you need to do to 100% replicate this glitch is to be in a Johto location and then warp to Pallet Town, prior to having visited Kanto before.

This can be done with either the GameShark codes 010D00DA and 010201DA (Gold/Silver) or 010DB5DC 010DB6DC (Crystal) or arbitrary code execution. To use these codes, activate them in a Pokémon Center, then go up to the second floor and back down again. You should warp to Pallet Town.

[img]https://i.imgur.com/C7YDPqb.png[/img]

Next you need to go to the Pokégear map and scroll down from Pallet Town (from now on you must scroll down, if you scroll up you may not be able to access all the available locations from this glitch). If done correctly the game should erroneously give Johto locations while the map is still in Kanto. If you go down further you should encounter glitch locations.

[img]https://i.imgur.com/cVG8hFJ.png[/img] [img]https://i.imgur.com/lKMDpaj.png[/img] [img]https://i.imgur.com/Y2l22U8.png[/img]

Many of these glitch locations take their name from VRAM (and are presumably subject to VRAM inaccessibility hence the many 9s in their name). However, if I remember rightly two of these glitch locations were taken from Echo RAM. The only one I remember though is sourced from E88E (Echo RAM for C88E).

The contents of this address can be modified with arbitrary code execution (without the need of OAM DMA hijacking to lock it) so you can create cool screens such as this (Cloud City was the subject of a Pokégod rumour in the past):

[img]https://i.imgur.com/hS50axJ.png[/img]

An E88E location is also available for the Crystal selection of locations and glitch locations.

Side-note:

Map 21FF (DA00=21, DA01=FF) in Gold and Silver is a non-freezing glitch map.

I don't know what controls its Pokégear location, however this time it was set to SPECIAL and scrolling down would also eventually bring up the E88E location.

So perhaps you don't need to have accessed Kanto earlier than you're supposed to (although more research is needed regarding whether that is a requirement at all).

[img]https://i.imgur.com/0q2OKEb.png[/img] [img]https://i.imgur.com/8FzGvPw.png[/img]


Edit: A video :)

https://www.youtube.com/watch?v=r32agevxdw4

Re: Pokégear map glitch (Gold/Silver/Crystal)

Posted by: SatoMew
Date: 2018-03-23 15:02:20
I initially found it in Korean Gold and Silver and then checked Japanese Crystal.

p-p-pfero from the pret Discord looked into the bug and found it was in this snippet:

.down
    ld hl, wPokegearMapCursorLandmark
    ld a, [hl]
    cp e
    jr nz, .wrap_around_down
    ld a, d
    inc a
    ld [hl], a
.wrap_around_down
    dec [hl]


The fix:

.down
    ld hl, wPokegearMapCursorLandmark
    ld a, [hl]
    inc e
    cp e
    jr nc, .wrap_around_down
    inc d
    ld [hl], d
.wrap_around_down
    dec [hl]


And I'm glad that it was exploitable for ACE! :)

Re: Pokégear map glitch (Gold/Silver/Crystal)

Posted by: Torchickens
Date: 2018-03-23 15:36:33
Thanks for the info! :)


And I'm glad that it was exploitable for ACE! :)


Yeah, if I remember rightly while the details are hazy you can execute arbitrary code with this or at least a freeze either by closing the Pokégear map from certain locations or as a side effect of the name in Crystal. Then you have the maps with arbitrary names which while they do not execute code can be customized to any location name you want as long as long as it fits.

Re: Pokégear map glitch (Gold/Silver/Crystal)

Posted by: SatoMew
Date: 2018-03-24 19:57:38
You're most welcome and likewise ;)

I updated my post to include the complete patch.

Re: Pokégear map glitch (Gold/Silver/Crystal)

Posted by: Krys3000
Date: 2019-05-08 12:20:59
For the record, this also works in french games :)