ItemDex/RB:093: Difference between revisions
→Bootstrapping: Added the Tentacool setup.
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==Bootstrapping==
There exists multiple different bootstrapping strategies with 8F. Most of them jump to $D322, which is the third item in the item pack. The advantage of using the third item slot is that this allows 8F to be the first item, and another item that is unrelated to the code to be the second (which is useful if the payload modifies the item).
=== 2–5 Pokémon "Tentacool PPs" setup ===
{{main|User:CytricAcid/Beginner's Guide To ACE/US Red and Blue Guide#Setup}}
An 8F setup can consist of as few as 2 Pokémon, with one of them having specific PP values:
# 2–5 Pokémon
# Tentacool as the first Pokémon
# Onix as the second Pokémon
# The Tentacool must have exactly the following amounts of remaining PP and number of PP Up used:
#* 33 for 1st move (0 PP Up used)
#* 34 for 2nd move (0 PP Up used)
#* 19 for 3rd move (3 PP Up used)
#* 41 for 4th move (3 PP Up used)
{{Explanation|title=ASM translation|contents=
<pre>
; Initial hl = 0xD163, a = 0x63, bc = 0x00B8
$D163 <- 02/03/04/05 || ld [bc], a / inc bc / inc b / dec b
$D164 <- 18 22 || jr 0x22 ; pc = $D166 + 0x22 = $D188
(...)
$D188 <- 21 22 D3 || ld hl, 0xD322
$D18B <- E9 || jp hl ; pc = $D322
</pre>
Here the register <code>a</code> was a temporary variable for reading out the jump destination $D163, and <code>bc</code> was the offset into <code>ItemUsePtrTable</code> (here (0x5D - 1) * 2, where 0x5D is the item ID of 8F).
* If the party contains only 2 Pokémon (i.e. nothing other than Tentacool and Onix), then the first instruction will try to write 0x63 to the ROM address $00B8, which [[SRAM|locks the SRAM]] instead.
** This is generally not a bad thing (it makes things safer in case there is something wrong with the item code), but it might stop you from writing to the SRAM with a simple memory writer, so in that case you probably want to have more than 2 Pokémon in your party to avoid this.
* The other possible first instructions do nothing as long as the item code jumped to does not make any assumption on the values of <code>a</code> and <code>bc</code>.
}}
===5 Pokémon "233 HP Pidgey" setup===
The "233 HP Pidgey" setup used to be the most popular 8F setup, although it is considered outdated due to the difficulty of controlling the exact HP value of a Pokémon. It consists of 5 valid Pokémon, with one of them having a specific current HP value:
# 5 Pokémon
# Pidgey as the first Pokémon
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