Dmitry Grinberg
@dmitrygr
Followers
5K
Following
18K
Media
328
Statuses
3K
Creating order out of chaos, or reverse (as needed).
Austin, TX
Joined October 2009
The bus protocol for @FisherPrice Pixter Classic has been figured out and carts can now be dumped. Proof:
2
1
10
What the hell is an industry-standard 8-wire resistive touch panel?! I know of 4 and 5 wire panels.
2
0
2
This does not happen on later ARM cores (like ARM9) or if your core has alignment checking option and it is enabled. Fun, eh?.
0
0
0
But if you try to load an immediate, things go a bit weird, since you end up loading a value from an unaligned address. This will load the proper word, but then rotate it right by 16 bits. This will bewilderingly break all your immediates and nothing else. .
1
0
1
So, on ARM7TDMI, PC is written with a value whose last two bits are 0b10. This causes no issues immediately, as instruction fetches ignore lower 2 bits. ARM code runs, as you;d expect ad you'll think all is well. As branches are relative, they work too, and the lower bits stay. .
1
0
0
I'll give a hint: on most ARM cores, it'll jump (in ARM mode) to (addr_of_this_instr + 2), but not on all. .
2
0
1
Pop quiz. You execute “BX PC” on an ARM CPU in Thumb mode from an address divisible by 2 but not 4. Explain what happens.
3
0
5
That moment when you've finally gotten code execution and are dumping the 16MByte ROM out a bit-banged UART . at 1200bps 8n3 . .
1
0
5
SD cards have a spec-defined method to indicate support for CMD23. It is not mandatory to support it. It is OK not to. Thus no reason to lie. And yet, there are cards that claim support, but reject the command as invalid, because "fuck you, that's why!".
1
0
15
I love it when a plan comes together. This is the first pirate ROM for the @FisherPrice Pixter Color. It ain’t much, but it does run.
2
5
41
This is someone emulating an 8-bit stack based machine on 32-bits. weirdly. They use as many stack slots as the old machine would, but here they are 32 bits. So instead of using 2 slots to store a u16, one is used and second is garbage. It works, just dirty. EG:
0
0
1
And this is the first pirate rom running. using the reverse engineered instruction set of the VM they use for games
0
0
5
