Hi,

I wonder if there's a circuit diagram for a simple 6502 based microcomputer. No ROM necessary, I just need a simple design for wire wrapping or breadboard. Where can I find circuit diagrams?

http://wilsonminesco.com/6502primer/index.html
It should answer every question that comes up in the process. If it does not, let me know, and I will improve it. What do you plan to use in place of a ROM though?

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Amazing stuff, thanks! It does not have to be ROM-less, I just want something relatively simple to build. Maybe it's just me being a donut but is there an entire circuit diagram for your design in your website?

Just purchased a 6502 from ebay! Happy times!

The 6502 is still being made today. In fact, if you count the 6502 cores inside custom ICs, they are being made in volumes of hundreds of millions of units per year-- it's just that they're not very visible and people often don't even realize they own them, like in computers under the hoods of cars and in consumer electronics. The website of the IP owner that does the licensing for the various manufacturers is http://www.westerndesigncenter.com/wdc/ .

I never put the entire computer on one schematic. There's really no reason to, and there are too many variations it could take. [Edit: I gave in and did one, at http://wilsonminesco.com/6502primer/pot ... ml#BAS_CPU. It's a very basic 65c02 computer.]

You would pretty much have to have ROM (like EEPROM) since there needs to be some program in place to get things going upon power-up. Without this, a processor by itself doesn't know the steps to go through to get its first program from disc flash or over a serial line or anywhere else to run, or even to run a keypad and display to let you key in a minimal program. There are ways around it, but they could have big problems. One example would be to get a non-volatile SRAM module like Dallas Semiconductor (now part of Maxim) makes and plan to have that be the only memory, and put the reset vector and routine into that with something esle, then plug it into your creation and turn it on. The problem there is that without a means to protect just that portion of RAM while letting the computer write to the rest of it as it needs to, programming errors could mean that you overwrite the reset vector or reset routine itself, making the computer unable to recover.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

I have a stack of 65xx, ram , rom an other stuff that BitWise sent me for free, so if you need some ic, just send me a pm. Check on this topic.

Yes, and I probably should have made the distinction. It's not trivial. There's no reason to use the old NMOS 6502 if you're making your own hardware, since the CMOS version is so much better in every way.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

CMOS is more expensive too, so if you don't care if it is CMOS or not, the old NMOS is much cheaper on ebay.

The overall cost of the computer won't be much different though after you consider the cost of sockets, board, support ICs, LCD, power supply, etc., and especially your own labor. I think it's well worth going with the CMOS.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Yes, you are probably right, unless you already have all the other components. I took a look on ebay, and it turns out that there are lots of Rockwell 65c02 currently on ebay, and they cost as much as the regular 6502...

In a way the NMOS may be kinda fun, vintage ic, old silicon, heating up like hell, sucking power .

Edit: alkopop79 have you looked at the SBC-2 schematic? I used it as a base for my sbc.

Just to clarify points made about the 65C02, I would emphasise that there's nothing wrong in a hobby project based on an NMOS 6502 - it will take more power but you'll be able to do anything you want - it was good enough for Apple ][, PET, UK101, BBC micro, VIC20, Atari 400, Kim-1, Sym-1, Superboard, JOLT, ... !

Yes, the 65C02 has some useful opcodes, but nothing you can't do without if you're not pushing the envelope. And yes, it may be the easiest to buy and the only one still produced, but if you already have a 6502, don't be discouraged.

Cheers
Ed

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!