[CLOSED]Trying to understand the Address for speed

Discuss technical or other issues relating to programming the Nintendo Entertainment System, Famicom, or compatible systems.

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gukingofheart
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Re: Trying to understand the Address for speed, ExciteBike

Post by gukingofheart » Sat Dec 15, 2018 11:58 pm

Step Into, Step Out, Step Over

Which does what?

There's also "run line" & "128 lines" as well.

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rainwarrior
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Re: Trying to understand the Address for speed, ExciteBike

Post by rainwarrior » Sun Dec 16, 2018 12:06 am

This might help:
http://www.fceux.com/web/help/fceux.html?Debugger.html

All of those terms are defined there, but if you need clarification though you can ask.

gukingofheart
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Re: Trying to understand the Address for speed, ExciteBike

Post by gukingofheart » Sun Dec 16, 2018 12:10 am

now I understand, but which one do you want me to use?


(thanks for the info so far.. working on a simple guide to help me remember this info for the future)

gukingofheart
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Re: Trying to understand the Address for speed, ExciteBike

Post by gukingofheart » Sun Dec 16, 2018 1:56 am

Game Genie or not returns these same results
---------------------
00:CE30:18 CLC (Step Into)
00:CE31:75 90 ADC $90,X @ $0090 = #$00 (Step Into Twice)
00:CE33:95 90 STA $90,X @ $0090 = #$00 (Step Into 3 times)
00:CDAF:4C BD CD JMP $CDBD (Step Out)
00:CE30:18 CLC (Step Over)

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pubby
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Re: Trying to understand the Address for speed, ExciteBike

Post by pubby » Sun Dec 16, 2018 2:48 am

There isn't a cookbook for this type of work. It doesn't boil down to following someone else's directions. You need to do analysis and trial-and-error.

Step into/out/over are just for navigating the code. You don't have to use them -- you can use the scrollbar instead and track the program counter in your head. What you're trying to determine is what the code does.

In particular, you're trying to determine what part of the code is capping the speed, so look around for some sort of comparison like CMP #48. But who knows what it could be! You have to figure it out.

Also, play with the game genie code. Try halving numbers. Does halving a number halve the bike's speed? If so, that's the data!

gukingofheart
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Re: Trying to understand the Address for speed, ExciteBike

Post by gukingofheart » Sun Dec 16, 2018 3:08 am

First I have to know what to play around with.. what to experiment with... what values to try to change, and what values are pointless.
Puppy, not sure if you're trying to even help.. and "rainwarrior" is helping me a lot more atm.

(I'm also writing all this info down.. and will be asking questions for different games in the future... and will try to find a pattern of what to try, and what would be a total waste of time).

Haven't even figured out yet why this cheat needs a second line of code yet.

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nesrocks
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Re: Trying to understand the Address for speed, ExciteBike

Post by nesrocks » Sun Dec 16, 2018 11:11 am

My question is do you need to use game genie codes? Why? What is your goal? You can make modifications to games yourself by understanding what the code does and I think that putting game genie code in the middle of this is only going to make your learning more complicated. If you want to change the bike's top speed forget GG, learn assembly and learn how to use fceux's debugger.

http://www.6502.org/tutorials/6502opcodes.html
http://www.fceux.com/web/help/fceux.html?Debugger.html
https://twitter.com/bitinkstudios <- Follow me on twitter! Thanks!

gukingofheart
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Re: Trying to understand the Address for speed, ExciteBike

Post by gukingofheart » Sun Dec 16, 2018 4:16 pm

address codes easily convert to GG.

For some games & codes, it probably won't become a GG.. but for others, it will be.
I'm not making GG codes for myself (other then a learning experience), making it for others.

Basically creating a new hobby in life.


Anyways, until I learn something new... I guess this might be all the info I can understand at this time.... so thanks again

(Mods can close this thread, as I need to organize info, and this thread would just get messier)

Bavi_H
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Re: [CLOSED]Trying to understand the Address for speed

Post by Bavi_H » Sun Dec 16, 2018 5:07 pm

Here are some points I hope you might find helpful if they weren't clear before:


Game Genie codes can't directly affect RAM

On the NES, the RAM is at CPU addresses 0000 to 07FF. However, a Game Genie can only modify the values at CPU addresses 8000 to FFFF. So to make a Game Genie code affect a RAM address, you have to find something in addresses 8000 to FFFF that affects that RAM address, then change that.


Code vs. data

The CPU is always executing instructions. It has an internal counter called the program counter (PC) that is the address of the instruction it is executing.

When you are looking at the contents of CPU addresses in the hex editor or the debugger, be aware that the contents will be interpreted as instructions only if the CPU's program counter ever gets to that address.

Alternatively, the contents of addresses might be used as data. That is, there are various load and store instructions that can get the value from an address or put a value into a RAM address. If that happens, the value in that address could represent something like, for example, the hit points for a bad guy, and not an instruction.

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