Chip8 opcode F020?

Discussion in 'Computer Programming, Emulation, and Game Modding' started by Monado_III, Feb 14, 2016.

  1. Monado_III
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    Monado_III GBAtemp Advanced Fan

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    So I made a crappy Chip8 emulator but I'm having some issue, it seems to be working well enough, but on certain games, (pong, tic-tac-toe) it gives
    Code:
    Wrong opcode: F020
    Wrong opcode: F020
    which would be easy enough to solve if I could figure out what opcode that is, but for some reason I can't find what opcode that would be. Is my emulator at fault or the games that I'm using?

    edit: I can post the source of my emu if that's nessecary
     
    Last edited by Monado_III, Feb 14, 2016
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  2. FAST6191

    FAST6191 Techromancer

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    http://devernay.free.fr/hacks/chip8/C8TECH10.HTM and the docs in http://www.pong-story.com/chip8/ does seem to have anything and http://mattmik.com/files/chip8/mastering/chip8.html covers some undocumented instructions and none have anything for FX20.
    http://progopedia.ru/implementation/asm-chip-8/ mentions Fx20 under the super chip Fx30 instruction. However I do not want to try what little Russian I have against the wording there (something about simlar and sprites).

    To that end it is more likely the program at fault, however I would still try to debug it in the emulator to make sure you have not messed something up somewhere (you have not missed a branch or anything and tried to decode a payload or something).
     
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  3. Monado_III
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    Monado_III GBAtemp Advanced Fan

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    Ok, I'll try looking into that.
     
  4. Monado_III
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    Monado_III GBAtemp Advanced Fan

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    Looking at the program flow, would I be correct in assuming it's being caused by trying to execute before 0x200?
    flow
     
  5. Monado_III
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    Monado_III GBAtemp Advanced Fan

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    Okay, I fixed it, it was something wrong with my 00EE opcode handler (would it be a handler? idk).