Posted: 9/25/2018 4:56 PM
Post subject: [Lua] How to detect a write to a mapper register
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SusiKette
He/Him
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Joined: 6/11/2017
Posts: 6
Location: Finland
I want to create a script that hits a breakpoint when a certain value is written to a mapper register. I don't think the official documentation mentioned anything about mapper registers, at least not in the function list. Basically it would be something like this: 
if((written_value AND 7) == 6 || (written_value AND 7) == 7) then
  debugger.hitbreakpoint();
  written_value = 0;
end;
The value written to the $8000 would be saved to "written_value". even if this wouldn't work as is, it should give a good idea on what I'm trying to do. If it is possible to actually create a breakpoint condition in the debugger that does the same thing, it'll do just as well.
Posted: 9/25/2018 5:21 PM
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feos
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Joined: 4/17/2010
Posts: 11055
Location: RU
NES TAS of 2011
What is a mapper register?
Warning: When making decisions, I try to collect as much data as possible before actually deciding. I try to abstract away and see the principles behind real world events and people's opinions. I try to generalize them and turn into something clear and reusable. I hate depending on unpredictable and having to make lottery guesses. Any problem can be solved by systems thinking and acting.
Tyranny of the ineducable is the worst thing ever, because they always monopolize things they are absolutely incompetent in.
Posted: 9/25/2018 5:37 PM
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SusiKette
He/Him
Experienced Forum User
Joined: 6/11/2017
Posts: 6
Location: Finland
Not sure if you are trolling or something, but take a look at this link: https://wiki.nesdev.com/w/index.php/MMC3#Registers It is for the MMC3 memory mapper and it clearly has registers. The NES has some too. Such as $2000, $2001 and $2002
Posted: 9/25/2018 6:05 PM
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feos
Experienced Forum User, Site Admin, Skilled player (1194)
Joined: 4/17/2010
Posts: 11055
Location: RU
NES TAS of 2011
Currently fceux can only set breakpoints on things mapped to memory. I just tried $8000 with Alien 3, and write breakpoint worked just fine. If you're sure some mapper register exists in memory, but its breakpoints don't work, we can fix that I think. And to grab the value that's being written, just fetch Accumulator's value the usual way (memory.getregister("a")).
Warning: When making decisions, I try to collect as much data as possible before actually deciding. I try to abstract away and see the principles behind real world events and people's opinions. I try to generalize them and turn into something clear and reusable. I hate depending on unpredictable and having to make lottery guesses. Any problem can be solved by systems thinking and acting.
Tyranny of the ineducable is the worst thing ever, because they always monopolize things they are absolutely incompetent in.