Greetings. I want to share information about maps. When a map is loaded, it also loads many things with it. It includes events, npcs, exits and chests. All of them are stored in different structures.
Headers
All mentioned structures have in common a header and their related data. The header structure is probably #$0340 bytes with 416 entries for each map, except the last one, with two bytes by entry. After the header structure, it follows the data structure. They are two different structures. However, in the game code, they are referenced from the header initial address (base). As example, LDA $DFBB00,X can load the first byte of the header structure (2 bytes index) or the first byte of the entrance structure (6 bytes of data). It is necessary to pay attention in the index to determinate the kind of structure which are being loaded. In this case, header structure if X < #$0340 or the entrance structure if X > #$0340.
The header structure is only two bytes for each map. They are actually indexes to search for the data structure. To calculate the header index for a specific map, the function is: header index = (map number * 2) + header base.
As example, the header base for the entrances are $DFBB00. For the map #$0074 (House of Gau's father, indoors), the index for the entrance structure is:
To calculate the data address: data address = value stored in header index + header base. It is the start of the data structure for the specified map.
The game system checks the difference between the header index and the next header index. The referenced structures have a fixed size but multiple instances of the structure can be stored. As example, the structure size of entrances are six bytes. If the difference is 0, there are no exists for this map. If the difference is 6, there are one exit in this map. If the difference is 12, there are 2 exits in this map. If the difference is 18, there are 3 exits in this map, etc.
C4/0000 Events
When the characters steps in the (x,y) position of the map, the designed event is executed.
If the event doesn't move the character or have a conditional branch to null itself after its execution, it will be called repeatedly in a infinite loop.
C4/1A10 Npcs
Sets the initial data for the NPCs when a map is loaded.
For the movement type, i only found #$00 (static) or #$03 (movement) as valid values. All other values sets the npc as static or have weird behavior.
DF/BB00 Exits
When the character steps in the (x,y) position, warp it for the designed map with the designed coordinates.
It is imperative to have valid coordinates for the setup. If the character can't access the map position, the setup is useless. If the new map position isn't walk able, the character is permanently stuck. If the new map position bypass the map size, the coordinate system is corrupted and all exits are disabled or aren't functional.
ED/82F4 Chests
Sets the chest for the map. Actually, if the character press the A button in front of the designed position, the chest event is executed. If the tile in the position is a chest, the tile changes as a opened chest. Otherwise, the tile isn't changed.
Unlike the other headers, the index of the data structure is relative to $ED/8634 instead of $ED/82F4, the actual header base.
Others?
There are other settings for the map, like the background in battles, the song played, enemy formations used, etc. I don't know where this setup is stored, but i suspect of the $ED/8F00 structure. The structure size is #$021 and doesn't have a header structure.
I don't have enough information about this structure but i will let you know i consider it a good suspect for the low level setting of the maps.
Headers
All mentioned structures have in common a header and their related data. The header structure is probably #$0340 bytes with 416 entries for each map, except the last one, with two bytes by entry. After the header structure, it follows the data structure. They are two different structures. However, in the game code, they are referenced from the header initial address (base). As example, LDA $DFBB00,X can load the first byte of the header structure (2 bytes index) or the first byte of the entrance structure (6 bytes of data). It is necessary to pay attention in the index to determinate the kind of structure which are being loaded. In this case, header structure if X < #$0340 or the entrance structure if X > #$0340.
The header structure is only two bytes for each map. They are actually indexes to search for the data structure. To calculate the header index for a specific map, the function is: header index = (map number * 2) + header base.
As example, the header base for the entrances are $DFBB00. For the map #$0074 (House of Gau's father, indoors), the index for the entrance structure is:
Code:
header index = (map number * 2) + header base
header index = (#$0074 * 2) + #$DFBB00
header index = (#$E8) + #$DFBB00
header index = #$DFBBE8To calculate the data address: data address = value stored in header index + header base. It is the start of the data structure for the specified map.
The game system checks the difference between the header index and the next header index. The referenced structures have a fixed size but multiple instances of the structure can be stored. As example, the structure size of entrances are six bytes. If the difference is 0, there are no exists for this map. If the difference is 6, there are one exit in this map. If the difference is 12, there are 2 exits in this map. If the difference is 18, there are 3 exits in this map, etc.
C4/0000 Events
Code:
Events header: C4/0000
00 position x
01 position y
02 event pointer: low
03 event pointer: middle
04 event pointer: highWhen the characters steps in the (x,y) position of the map, the designed event is executed.
If the event doesn't move the character or have a conditional branch to null itself after its execution, it will be called repeatedly in a infinite loop.
C4/1A10 Npcs
Code:
NPCs header: C4/1A10
00 event: low
01 event: middle
02 #$01 event: high
#$02 event: high
#$04 palette
#$08 palette
#$10 palette
#$20 intangible
#$40 ???
#$80 presence
03 ? id
04 x position
05 y position
06 graphic set
07 #$01 movement type
#$02 movement type
#$04 movement type
#$08 movement type
#$10 map layer
#$20 map layer
#$40 vehicle
#$80 vehicle
08 #$01 direction facing
#$02 direction facing
#$04 don't turn npc if spoken
#$08 ???
#$10 ???
#$20 ???
#$40 ? can fix "sliced" graphics?
#$80 ???Sets the initial data for the NPCs when a map is loaded.
For the movement type, i only found #$00 (static) or #$03 (movement) as valid values. All other values sets the npc as static or have weird behavior.
DF/BB00 Exits
Code:
Exits header: DF/BB00
00 x position: old
01 y position: old
02 map id: low
03 #$01 map id: high
#$02 ???
#$04 ???
#$08 display location name
#$10 direction facing
#$20 direction facing
#$40 ???
#$80 ???
04 x position: new
05 y position: newWhen the character steps in the (x,y) position, warp it for the designed map with the designed coordinates.
It is imperative to have valid coordinates for the setup. If the character can't access the map position, the setup is useless. If the new map position isn't walk able, the character is permanently stuck. If the new map position bypass the map size, the coordinate system is corrupted and all exits are disabled or aren't functional.
ED/82F4 Chests
Code:
Chests header: ED/82F4
00 x position
01 y position
02 chest id
03 chest type
04 chest contentSets the chest for the map. Actually, if the character press the A button in front of the designed position, the chest event is executed. If the tile in the position is a chest, the tile changes as a opened chest. Otherwise, the tile isn't changed.
Unlike the other headers, the index of the data structure is relative to $ED/8634 instead of $ED/82F4, the actual header base.
Others?
There are other settings for the map, like the background in battles, the song played, enemy formations used, etc. I don't know where this setup is stored, but i suspect of the $ED/8F00 structure. The structure size is #$021 and doesn't have a header structure.
I don't have enough information about this structure but i will let you know i consider it a good suspect for the low level setting of the maps.