Hey, thanks. Yeah, I haven't yet fully explained all of the simulator.
0xfe is a random number - a new random byte is generated on every instruction.
0xff contains the ASCII code of the last key pressed.
My simulator is adapted from the one at http://6502asm.com/beta/index.html - that has a help screen with some more info. I mostly cleaned up the (atrocious) JavaScript and added a memory monitor and disassembler (and implemented a few instructions they'd left out).
0xfe is a random number - a new random byte is generated on every instruction.
0xff contains the ASCII code of the last key pressed.
My simulator is adapted from the one at http://6502asm.com/beta/index.html - that has a help screen with some more info. I mostly cleaned up the (atrocious) JavaScript and added a memory monitor and disassembler (and implemented a few instructions they'd left out).