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Machine Code Monitor Programming Guide

Discussion in 'Engineering & Reverse Engineering' started by Sonic 65, Oct 25, 2004.

  1. Sonic 65

    Sonic 65

    Tech Member
    I made a guide that tells you the location of parts of monitor code and what those parts do. Not much, but hey. Updates coming later.
     

    Attached Files:

  2. But you're talking about S1, right? It can't be S2 because monitor code in that game is at a higher address. Eggman monitor does nothing in S1, so it isn't too hard to figure out what a jump to "4E 75" does. :P

    Try to put in the next update info on how to have unused monitors to do something.
     
  3. Hivebrain

    Hivebrain

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    Wouldn't it be better to look at a disassembly if you want to know how things work?
     
  4. LOst

    LOst

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  5. Hayate

    Hayate

    Tech Member
    LOst, do you have a machine code to ASM table anywhere? That would help me out a lot more than this other stuff...
     
  6. Sonic 65

    Sonic 65

    Tech Member
    I made a little machine-code-to-ASM text file sometime ago. The only problem is that it hasn't seen an update in ages. I'll update it a little and edit this post to have it attached.

    Oh yeah, and Erik JS, the Eggman code is more than a jump to 4E 75.

    addq.b #2, $24(a0) ;???
    move.w #$1D, $1E(a0) ;???
    move.b $1C (a0) ,d0 ;???
    cmpi.b #1 , d0 ;Does monitor contain Eggman?
    bne.s loc_A384 ;If not, branch
    rts ;4E 75

    NOTE: Actually, my file is ASM-to-machine code, but it can also be used vice-versa.
     

    Attached Files:

  7. Rika Chou

    Rika Chou

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    Very good, Sonic 65, I can tell you have put a lot of time into this.
     
  8. Sonic 65

    Sonic 65

    Tech Member
    Thanks. Making a machine code guide isn't nearly as hard if you have a disassembly. :D
     
  9. Quickman

    Quickman

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    Or you could just use the documentation Motorola give. That's how I learned ASM.

    EDIT:

    addq.b #2, $24(a0) ; advance to next object routine
    move.w #$1D, $1E(a0) ; set collision size for object to $1D
    move.b $1C (a0) ,d0 ; load animation frame into d0
    cmpi.b #1 , d0 ; Subtract one from animation frame number (frame 1 is Eggman)
    bne.s loc_A384 ; If not equal to 0 (I.e. if frame is not Eggman), continue to other frame checks
    rts ; We'll reach here if it IS equal to 0 - nothing happens
     
  10. Hivebrain

    Hivebrain

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    Isn't $1E(a0) something to do with animation? IIRC, $1A-$1E(a0) are used by the animation subroutines.
     
  11. Hayate

    Hayate

    Tech Member
    Sonic 65: Sorry to sound annoying, but it doesn't have all of the commands, like ADD or BEQ (now that's useful)...

    Edit: S65 for Tech Member! :D
     
  12. Quickman

    Quickman

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    I was going by MY document on the SST, hosted by drx on the Hacking CulT.
     
  13. Hivebrain

    Hivebrain

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    That document is inaccurate. And exactly how much of the information on it did you find yourself?
     
  14. Quickman

    Quickman

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    I have no idea. I've long since lost the original to check (it was on my old hard drive before I got my computer which for the moment doesn't suck).
     
  15. Sonic Hachelle-Bee

    Sonic Hachelle-Bee

    Taking a Sand Shower Tech Member
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    You've just asked for it. :(

    Flags:
    N: Negative. Set to 1 if result negative.
    Z: Zero. Set to 1 if result is 0 (false).
    V: Overflow. Set to 1 if overflow (Pos + Pos = Neg or Neg + Neg = Pos)
    C: Carry.
    X: Like C, Carry.

    Assembly <-> Hexadecimal

    MOVE.B <-> 11 FC 12 34 AB CD (Store byte 34 at RAM $ABCD)
    MOVE.L <-> 21 FC 12 34 56 78 AB CD (Store long 12345678 at RAM $ABCD)
    MOVE.W <-> 31 FC 12 34 AB CD (Store word 1234 at RAM $ABCD)

    CMPI.B <-> 0C 38 12 34 AB CD (compare byte 34 at data from RAM $ABCD)
    CMPI.W <-> 0C 78 12 34 AB CD (compare word 1234 at data from RAM $ABCD)
    CMPI.L <-> 0C B8 12 34 56 78 AB CD (compare long 12345678 at data from RAM $ABCD)

    BRA.S <-> 60 11 (Branch always, jump 11 bytes)
    BSR.S <-> 61 11 (Branch under sub-routine)
    BHI.S <-> 62 11 (Branch if C=0 and Z=0)
    BLS.S <-> 63 11 (Branch if C=1 or Z=1)
    BCC.S <-> 64 11 (Branch if Carry clear, C=0)
    BCS.S <-> 65 11 (Branch if Carry set, C=1)
    BNE.S <-> 66 11 (Branch if non equal, Z=0 (false))
    BEQ.S <-> 67 11 (Branch if equal, Z=1 (true))
    BVC.S <-> 68 11 (Branch if Overflow clear, V=0)
    BVS.S <-> 69 11 (Branch if Overflow set, V=1)
    BPL.S <-> 6A 11 (Branch if result plus, N=0)
    BMI.S <-> 6B 11 (Branch if result minus, N=1)
    BGE.S <-> 6C 11 (Branch if greater or equal to, N=V)
    BLT.S <-> 6D 11 (Branch if lower than, N is not the same as V)
    BGT.S <-> 6E 11 (Branch if greater than, N=V and Z=0)
    BLE.S <-> 6F 11 (Branch if lower or equal to, N is not the same as V or Z=1)

    ADD <-> 52 38 AB CD (Add 1 at value in RAM $ABCD)
    ADD <-> 54 38 AB CD (Add 2 at value in RAM $ABCD)

    JMP <-> 4E F9 11 11 11 11 (Jump at ROM $11111111)
    JSR <-> 4E B9 11 11 11 11 (Jump at sub-routine at ROM $11111111)

    NOP <-> 4E 71 (Non operation, do nothing and continue)
    RTS <-> 4E 75 (Return to sub-routine)

    EDIT: Examples:

    RAM $FE10: Level loaded.
    RAM $ FE 11: Act loaded.
    RAM $ EE 00: Camera X position.
    RAM $ EE 04: Camera Y position.
    RAM $ F64A: Water Y height.

    0C 78 04 01 FE 10 67 10
    If Metropolis zone 2 (level 04 01) is loaded, jump 10 bytes.

    0C 78 0E 00 EE 00 6F 08
    If Camera X position is lower or equal to 0E 00, jump 08 bytes.

    0C 78 15 00 EE 00 6F 10 31 FC 02 00 F6 4A
    If Camera X position is greater than 15 00, set water Y height to 02 00.
    Else, jump 10 bytes.

    Helpful? There might be some errors, I haven't a 68K disassembly program for Mac, then I found this myself. ;)
     
  16. Sonic 65

    Sonic 65

    Tech Member
    ... :blink:

    You. are. god.
     
  17. Icy Guy

    Icy Guy

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    Very nice, SHB, very nice, although I noticed one small error:

    0C 78 15 00 EE 00 6F 10 31 FC 02 00 F6 4A ("If Camera X position is greater than 0E 00, set water Y height...") should be 0C 78 0E 00 EE 00 6F 10 31 FC 02 00 F6 4A.
     
  18. Sonic Hachelle-Bee

    Sonic Hachelle-Bee

    Taking a Sand Shower Tech Member
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    Sonic 2 Long Version
    Yeah...
    Damn copy and paste... :D