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1 user currently in Rom Hacking:  hukka |
| Acmlm's Board - I2 Archive - Rom Hacking - 65c816 asm question |
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Sokarhacd Ball and Chain Trooper Resistance is Futile You Will Be Assimilated Hab SoSlI' Quch Level: 61  Posts: 114/1757 EXP: 1799888 For next: 76708 Since: 03-15-04 Since last post: 6 days Last activity: 4 hours |
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| I was wondering something, as I look through Earthbound in the Snes ASM Dev Kit, I was in JHack and it tells you some ASM addresses of the attack stuff, example: bash uses C2859F in asm to tell it what to do I guess, what I was wondering is, how does REP #$31 tell bash to do anything? doesnt REP reset the processor flag, but there is one thing I dont understand, that is what exactly does the #$31 have to do with the REP command...as you can tell im in the process of learning ASM.... edit:Ive also noticed anything to do with actions such as bash, any psi, and what not has the asm REP #$31...so right now im kinda guessing that whats before the REP controls the action.... (edited by Chaosflare on 04-29-04 11:59 PM) |
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MathOnNapkins Math n' Hacks Level: 67  Posts: 162/2189 EXP: 2495887 For next: 96985 Since: 03-18-04 From: Base Tourian Since last post: 1 hour Last activity: 32 min. |
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| REP #31 tells us to set to zero three bits of the status register P: #31: 0011 0001, therefore, the M,X, and C flags are reset by this instruction. To know how I derived this you need to check your docs for the P register layout. I don't know all the positions off the top of my head, but M,X, and C come up so frequently I have the memorized since a long time ago. The effect of this is to make the A, X, and Y registers 16-bits wide rather than 8, and the carry flag is reset because an add with carry operation will likely follow. Resetting the carry flag makes any subsequent ADC instruction a pure ADD, because the contents of the carry flag won't interfere with the result. But this really has very little to do with how "bash" or whatever you call it works in the game. What it should tell you is that those functions work with 16 bit values though. (edited by MathOnNapkins on 04-30-04 12:54 AM) |
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| Acmlm's Board - I2 Archive - Rom Hacking - 65c816 asm question |
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