Editing User:Blaziken257/T1 Save file research

Telefang has four external RAM banks (each bank is 8KB), resulting in 32KB external RAM. Save data is used in bank 0 (which corresponds to 0-1FFF in a .sav file), and possibly other banks.

== Save file header ==
Each version of Telefang has a header at the beginning, in the form of a string, denoting the game's version. This appears at ROM offset 0xF61-F70 in both versions, and is compared to 0:A000-A00F in RAM (0-F in a .sav file).
* In Power Version, this is " TELEFANG POWER\x00" (without the quotes).
* In Speed Version, this is " TELEFANG SPEED\x00" (without the quotes).
If this header is not present, the save file will be erased. There won't even be a message stating that the game is corrupt -- probably because it's not present the first time you play the game.

== Checksum ==
After the title screen, the game runs a checksum, adding up each byte from 0:A000-BFEF (0-1FEF in a .sav file). The result is a 16-bit number. This is compared to a 16-bit, '''big endian''' integer at 0:BFFE-BFFF (1FFE-1FFF in a .sav file). If this doesn't match, a save file corruption message will appear afterwards, with Crypto crying, and the data will be erased.

== Save file bit ==
At 0:BFFD in RAM (1FFD in a .sav file), this value is 00 if a save file is present, and 01 if it is.

== Converting saves across versions ==
Due to the difference in save file headers, save files from one version to another are not compatible.

To convert a Power Version save to a Speed Version save:
* Change the POWER string at the beginning to SPEED.
* Subtract 0x1C from the checksum at 0:BFFE-BFFF.

To convert a Speed Version save to a Power Version save:
* Change the SPEED string at the beginning to POWER.
* Add 0x1C to the checksum at 0:BFFE-BFFF.