No illegal opcodes

[omarandlorraine]

The illegal opcodes see a lot of use in the Commodore 64 scene, so I figure it'd be good to have these implemented in the emulator also.

[mlund]

What a coincidence; I need illegal opcodes for a SID player :-) I continued with your branch here, and all illegal codes should be implemented and tested: https://github.com/mlund/mos6502/tree/illegal. Feel free to use with #126. I'm unsure about the $FF caused the original README test to fail, see commit log for details.

[omarandlorraine]

I continued with your branch here, and all illegal codes should be implemented and tested: https://github.com/mlund/mos6502/tree/illegal. Feel free to use with #126.

That is exactly what I wanted, plus it addresses the concern I had about tests. Excellent! Maybe you'd be able to submit a pull request and we review and merge that, and close #126.

I'm unsure about the $FF caused the original README test to fail, see commit log for details.

I think the problem here is that the README example actually uses undefined opcodes to terminate the emulation. This behaviour is inherited from the 6502-rs project, from which this emulator was forked. There is some more explanation in the code review for #123

I strongly feel this is the wrong thing to do. I see you figured out another way to get the README example to terminate the emulation, with the JAM opcode, which is better. The bubble sort example uses the CMOS specific stop instruction (STP) to do this IIRC. I wonder if we wouldn't be better off with a "step over subroutine" function, like what debuggers have, and then end the subroutine with RTS, as normal.

[mlund]

Yes, halting the CPU is a bit drastic for a real program, but perhaps OK for emulator example; I aimed for minimal changes. My fork is forked from your fork, so it can be merged into yours and the current PR should update with the changes.

[omarandlorraine]

My fork is forked from your fork, so it can be merged into yours and the current PR should update with the changes.

Perfect. Can you make it so? Or do you want me to?

[mlund]

My fork is forked from your fork, so it can be merged into yours and the current PR should update with the changes.

Perfect. Can you make it so? Or do you want me to?

I think so, see #127

[mre]

You both are amazing. Thanks!