septicake:verifiedtrans::verifiedlesbian:would any of my followers happen to be familiar with 6502 assembly?
Klaus Frank@septicake I think I've a cheat sheet somewhere and at least one assignment at uni used it. But wouldn't that call familiar necessarily though...
@agowa338 does it happen to include how in the Kentucky Fried Fuck indirect addressing works?
@septicake I'm not at home right now, so I can only point you to things from google right now. Also we probably didn't need it for that assignment. But in the mean time is this helpful? https://www.nesdev.org/obelisk-6502-guide/addressing.html
You basically need to store the address within some region and point towards that address.
@agowa338 I gathered as much during my read through, but the problem I have is understanding how it's used and how it works, the examples given in the obelisk guide (the one you've linked to, as well as the one I found) haven't given me much to work with on that front. The instruction I'm working with right now and that is causing me grief is specifically the indirect LDA instructions, as I can't really follow how they're intended to work
@septicake Oh, sorry but that is way beyond the scope that we covered then :(
Kyle Lacy@septicake @agowa338 I learned 6502 assembly somewhat well when I worked on my NES assembler, so I can try to chime in a bit
Basic idea to summarize is when you do e.g. LDA ($40, X), this will read a 16-bit address starting at ($40 + X), then read the value at that address and store it in A
Concrete example:
- X is #01
- $0041 holds #$02
- $0042 holds #$04
- $0402 holds #$FF
- LDA ($40, X) will dereference ($0041) leading to the address $0402, which will load #$FF
@septicake @agowa338 as for why… that’s harder to answer. I think it could be useful for defining a table in memory. You’d load a table of addresses in your zero page, and you’d set the X register as an index into the table
I think NES Tetris uses some indirect addressing, and Displaced Gamers on YouTube showed some disassembled code using it (while explaining how to get ACE) if you want to see a real world example: https://youtu.be/QOES2XTqT74
