Invalid memory writes #2
Description
I am trying to integrate these tests in my emulator, but I keep having to make changes that I would rather not have to in order to accommodate these.
The main problem is writing to invalid memory addresses.
At first, I noticed a few writes to the fixed ROM bank sections. My emulator throws an exception if attempting to write to these other than in the initial ROM loading phase.
I said fine - I guess these tests should test the ROM bank areas so I changed my emulator accordingly.
However, I am at test "02 0093" and here it is trying to write to the prohibited section - address 65216 = 0xFEC0.
What's worse, is the test expects now to read the value it wrote - 252 at that address 0xFEC0.
Not only is this a prohibited read - but according to pandocs, there would be no way to read '252' on the official hardware:
"Nintendo indicates use of this area is prohibited. This area returns $FF when OAM is blocked, and otherwise the behavior depends on the hardware revision.
On DMG, MGB, SGB, and SGB2, reads during OAM block trigger OAM corruption. Reads otherwise return $00."
Am I missing something here? I would expect the read to be $FF or $00.
If not, is there any way to update these to be pseudo-random as to not hit restricted memory areas?
I will for now temporarily consider these areas as regular RAM for the sake of running the tests, but the code is getting ugly having to support all these cases!