Segmentation fault protection: Difference between revisions
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The 6502 uses memory-mapping to interact with external hardware, and reading/writing a memory location you normally shouldn't because your array indexed out of bounds can cause issues with external hardware, and even on some systems can result in a [[wp:Killer_poke|killer poke]] which can damage certain machines such as the Commodore PET. Memory-mapped ports don't work like normal memory; unlike normal memory, even ''reading'' a memory-mapped port can affect its contents, or affect the contents of other ports that are related to that hardware. (This isn't a property of the 6502 itself, but of the hardware connected to it.) |
The 6502 uses memory-mapping to interact with external hardware, and reading/writing a memory location you normally shouldn't because your array indexed out of bounds can cause issues with external hardware, and even on some systems can result in a [[wp:Killer_poke|killer poke]] which can damage certain machines such as the Commodore PET. Memory-mapped ports don't work like normal memory; unlike normal memory, even ''reading'' a memory-mapped port can affect its contents, or affect the contents of other ports that are related to that hardware. (This isn't a property of the 6502 itself, but of the hardware connected to it.) |
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It's very unlikely that you'll index an array out of bounds, however, as you can only index up to 255 bytes forward from the base address. What's more likely to happen is forgetting to pop all registers you pushed before returning from a subroutine, and the program counter getting loaded with some unknown value and executing from there. Again, the 6502 won't stop you from trying to execute RAM or memory-mapped ports, and there's no guarantee what will happen (most bytes with a low nibble of 2 will crash the CPU if it tries to execute them.) |
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