I'm just starting out a 6502 processor project in Logisim. I've done a less powerful processor this way before. But with 6502 come new concepts like interruptions. I would like to ask some questions and maybe you could direct me to some useful texts.
P.S. The whole project will be made out of logic gates almost entirely.
1. How are interrupts being implemented into a processor? What hardware should be added to make it work?
2. How is instruction pipeling being implemented into a processor?
3. How big is 6502's ROM that is used to decode binary opcode into instructions? (I don't know how it's called, it's the one used by Processor's Controller and can be done without ROM.)
4. How is OS or assembly language written into a processor? What hardware is required for that?
Edit:
Added the "less powerful" processor file at
https://github.com/Senijs/SAP-2 and added a picture of it.
The processor was built with reference to Paul Malvino's Simple As Possible computer-2.
The processor has all the instructions of 6502, except the Set/Clear Interrup instructions since there are is not interrupt logic in the hardware. Push/Pull Stack Pointer instructions are also not here since I didn't make a stack pointer for the processor. Some minor instructions are also dismissed like Set/Clear Overflow Flag and Set/Clear Decimal Mode since I found no use in them.
I can write out the opcodes if you want to test the processor.
I also found this diagram of 6502 architecture.
http://www.erich-foltyn.eu/Technique/6502.html How accurate is it?
I would like to know what the interrupt logic hardware does exactly.
And is it possible to write the whole Operating System/Assembler in RAM? I'm pretty sure it's impossible. You'd have to at least build ROM and other hardware that will store ASCII code and know how to transfer it to screen.
I coudn't find any information on 6502's ROM size that stores instructions and then executes it when the opcode is telling it to.