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snes ram dumping

Posted: Fri Jan 12, 2018 3:17 pm
by Amelia
Hello. I have taken an interest into the way action replays work. They are essentially rewriting some adresses in the RAM.
In theory, the action replay seems to be able to read the memory, while constantling sending rewriting instructions at the chosen adresses.
I was wondering about reaching the same result with an outside device, arduino or raspberry.
Is there an input / output "channel" for data on the snes ?
Does anybody ever succeeded in dumping the ram in some way ?

I am starting in this and am not an native english speaker, please be patient.


Re: snes ram dumping

Posted: Fri Jan 12, 2018 4:07 pm
by TmEE
The device hijacks an interrupt vector and does some of its own work (such as overwriting RAM) prior to handing control over to original target code in the game.

Re: snes ram dumping

Posted: Sun Jan 14, 2018 1:11 pm
by whicker

The S-CPU is always driving the address bus. Any writes to in-console RAM or registers must be done with this CPU. You cannot cause the CPU to pause and tri-state its bus to do your own writes. The CPU drives the signals very strongly, and will burn up after a minute if you try to force opposite logic states.

Contents of memory can be snooped on (copied) externally, by watching the CPU interact with its data and address bus.

Here is a project that uses the sd2snes for this, which could conceivably connect to a raspi over USB:
sd2snes usb support