It seems Add with Carry Immediate actually takes only 4 cycles + the fetch phase (3 cycles).
Senijs, it would be more accurate to say Add with Carry Immediate takes 4 half -cycles (since one cycle includes both the Phase 1 period and the Phase 2 period).

-- Jeff


As I understand it, a cycle ...

There's a difficulty with writing a simulation in a conventional programming language: hardware is parallel, and to make a model of a parallel process is not so easy.

If you could share your story of what your model is doing for 10 cycles that might help. It does seem a large number. An add ...

Thanks for the suggestions, BigEd, I'll check out the book and Nand2Tetris project.

I think I should learn more about the 6502 cycles timing. 1 cycle can be thought of, as you said, several cycles really. I remember there being a diagram of 6502 cycles which shows how much action actually happens ...

I am trying to make a 6502 work-alike processor in Logisim. I was trying to find info about 6502's control signals/pins/bus, but couldn't find anything except for Hanson's 6502 block diagram where you can see the control signal's names, but nothing about how they actually work.
The reason I want to ...

And there's always the 6502 Bible... the Programmers Guide (David Eyes and Ron Lichty) which covers the 65816, 6502, 65C02, etc. and is an excellent reference.

I'm just starting to read this book and it looks awesome. A ton of information and the basic architectures of 6502 and 6502 alike ...

One or two people here have found that a microcoded machine is a good choice: simple datapath, complexity in the simple-to-update microcode. Same with the Gigatron.

I never heared of microcoded machines before. If I understood correcty what google said, then microcode is the "code" written in ...

There are many possible implementations which can run a chosen instruction set - you don't necessarily have to follow exactly what the 6502 does on the inside. Indeed, it will be difficult to be exact. But if you want to follow the 6502's cycle counts, or follow the exact sequence of reads, writes ...

I've done a less powerful processor this way before. It might be helpful if you could tell us more about this other processor. Then we can comment on similarities and differences as compared to 6502.

-- Jeff

ps- the C74-6502 was originally a Logisim design.

Jeff, thank you for the reply. I ...

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 ...

Thank you for your replies. I will try your suggestion, BigEd.
Arlet, the thread that you posted looks like exactly what I need. I will read up on it.
I will try to search your forum for older threads and if I don't find the answers for my questions, then I will post a new thread. I think that's how ...

Hello everyone!

I'm Senijs from Latvia, currently a student.
I've been interested in programming and especially computer/cpu design for 2 years now. I found a simple game for my phone that was based around logic gates and it got me really interested about how computers ACTUALLY work.
I used a ...