Hey guys. I know I made a post once about leaving and not coming back but, well I was wrong.
Even though I finished the CPU of WedNESday a long time ago these are just a few points that I have yet to cover. The truth is that WedNESday is being absorbed into a multi-platform emulator and I want just 1 6502 core to serve all of the necessary platforms (Acorn Electron, NES etc.). So what I am developing is a generic 6502 core which has the occasional platform specific modifications (i.e. lack of BCD on NES).
Sorry if any of these questions have been asked before on this forum or another one.
1. What happens when the NES is powered on in terms of what the 6502 does? Is anything initialized? And does the CPU use the reset interrupt to initialise the PC?
What I would really appreciate is if someone has already/could give me a cycle breakdown of the 6502s start sequence.
2. MOS/Synertek/etc. all made 6502s but were there any differences between the 6502s that they made? (and I refer here to 6502 and not like the 6510's 2 zero page I/O)
3. Are illegal opcodes the same across all 6502s or are there some instances where the opcode differed?
4. Some people claim that the extra byte that BRK uses can be used for some purpose but like what?
Thank you.
Even though I finished the CPU of WedNESday a long time ago these are just a few points that I have yet to cover. The truth is that WedNESday is being absorbed into a multi-platform emulator and I want just 1 6502 core to serve all of the necessary platforms (Acorn Electron, NES etc.). So what I am developing is a generic 6502 core which has the occasional platform specific modifications (i.e. lack of BCD on NES).
Sorry if any of these questions have been asked before on this forum or another one.
1. What happens when the NES is powered on in terms of what the 6502 does? Is anything initialized? And does the CPU use the reset interrupt to initialise the PC?
What I would really appreciate is if someone has already/could give me a cycle breakdown of the 6502s start sequence.
2. MOS/Synertek/etc. all made 6502s but were there any differences between the 6502s that they made? (and I refer here to 6502 and not like the 6510's 2 zero page I/O)
3. Are illegal opcodes the same across all 6502s or are there some instances where the opcode differed?
4. Some people claim that the extra byte that BRK uses can be used for some purpose but like what?
Thank you.