Building a simple 6502 microcomputer

[alkopop79]

Great, thanks!

[GARTHWILSON]

Quote:

Where can I find wire wrap board? Can I just use a perf board instead?

At the lower speeds, any board that has the holes on .100" centers will work as long as there are no traces connecting the holes. Since you seem to have latched up with Mouser (possibly among others), put "Twin Industries" in their search box and you'll see lots of options. Twin is waaaaaay cheaper than Vector. There are other brands too, but Twin offers high quality and lots of variations. As for the shipping price, I consider it standard practice to get as many things at once as I think I might need anytime in the near future, so the shipping cost is proportionally less.

Quote:

How do you 'fix' the sockets to the perfboard? Can they be soldered to the board?

I have on occasion used a little hot glue, but they'll usually stay in well enough to avoid falling out if you turn it upside down until you get wires wrapped onto them, but if you get any of the kinds of perfboard that have solder pads around each hole, you could apply just a tiny bit of solder to the pins in opposite corners. Don't let the solder or flux come up the pin, or you won't be able to get the chemical welds in the wraps. The sharp corners of the pins need to be able to bite into the wire. My primer goes into the matters of cleanliness and so on that affect reliability also.

[BigEd]

Garth, any idea what hole diameter is appropriate? Digikey offers parts with 37mil or 42mil (0.94mm or 1.07mm)

Edit: ah, the smaller holes are for a board with plated through holes and pads for each hole - also more expensive. (http://www.alliedelec.com/search/produc ... U=70012513)

I found an interesting-looking forum here: http://forum.allaboutcircuits.com/tags.php?tag=wirewrap

[GARTHWILSON]

The hole sizes sound right. The plated-thru holes have their place, but won't be needed in a lot of home-made digital boards. You can still have a ground plane without the plated-thru holes. .042" is what I've always seen for the non-plated-thru ones, and then depending on the board material, sometimes the fibers on the inside of the hole kind of hold the pins in before you've added any wires to them. The insides of the holes are sometimes kind of "fuzzy" I suppose because for that kind of board it is neither necessary nor cost-effective to change the drill bits as often as they do for high-quality custom PCBs.

[BigDumbDinosaur]

BigEd wrote:

got me there - hot glue? Or maybe they push-fit.

When I used to use wire-wrap sockets on perf board I'd secure them with cyanoacrylate adhesive. If you do that, I shouldn't have to mention that once it's glued to the board it's very permanent. Also, please be careful that you don't accidentally glue yourself. If you do, you can usually break the bond with acetone (extremely flammable).

[alkopop79]

I wonder, how do WW components like the crystal or and LED? Can they be wire wrapped or do they need some sort of socket?

[rwiker]

alkopop79 wrote:

I wonder, how do WW components like the crystal or and LED? Can they be wire wrapped or do they need some sort of socket?

I don't think they can be wire-wrapped (wire-wrap sockets have square pins). One option is to simply put them in stand DIL WW sockets.

[GARTHWILSON]

Things like LEDs and resistors can be wire-wrapped but then need to be soldered, unlike .025" square posts. If the part can have a crystal connected directly, go ahead and use the crystal (like the 65c51 normally calls for); but otherwise don't bother trying to make an oscillator. Just get one in a can (like Ed recommended at viewtopic.php?f=1&t=2280&start=3) that plugs into an 8-pin or 14-pin SIP socket. They take less work and space and are more reliable than making your own, and possibly even cheaper.

The pirmer addresses both of these, but I just added the part about wire-wrapping things like resistors yesterday.

[BigEd]

I don't if these cuttable single-in-line strips are useful:
http://www.harwin.com/D01-995-Specialis ... amily.html
(The image doesn't look like wirewrap, but it is.)
You can click through to worldwide suppliers and see their stock levels.

[BigEd]

I've mentioned this site before, but I'll do so again:
http://electronics.stackexchange.com/qu ... wrap-board

[alkopop79]

BigEd wrote:

I've mentioned this site before, but I'll do so again:
http://electronics.stackexchange.com/qu ... wrap-board

I thought SIP sockets might do. Like the idea of the perforated, snap-off pin headers (the Harwin ones BigEd recommended). That would allow me to have 2 pin terminals.

[GARTHWILSON]

If you use SIP WW sockets, you will need some way to keep them perpendicular to the board so they don't slant over and touch the next row over. You can either glue them in or solder the base of at least a couple of pins to the pads around the holes. I did this on a few things on my workbench computer.

[alkopop79]

Now it's the waiting game. Wait till I get my wages... The amount of information you all provided have made me confident that I can build it!

[Dajgoro]

alkopop79 wrote:

Now it's the waiting game. Wait till I get my wages... The amount of information you all provided have made me confident that I can build it!

Well, my first working prototype used CMOS 4000 series glue logic, and it actually worked (i later switched to ttl) + it is not ww, but point to point soldering, so just don't connect something wrong, and it must work (at least @1MHz )!
And also EhBasic can be very easily modified to fit in any system.

[ElEctric_EyE]

alkopop79 wrote:

Now it's the waiting game. Wait till I get my wages...

Nice, I've been there. Lots of luck with your first computer design. I'm glad to read you are choosing WW. I have done the same many years ago on my first standalone computer. I won't bore anyone with the details, but 1 thing to pay strict attention to is power distribution and bypass capacitors. You will be tempted in the beginning, especially if you're successful, to expand your project with WW. After all, all you do is add more sockets and extend the power supply. I reached a point where the IC count was getting close to 20 ICs. I was just stringing along the power, just like I was doing with the data/address buses, with the same thickness power wire, I believe ".010 or .015". It was all working, then BAM! It stopped working, I checked and rechecked all wiring. Couldn't figure it out... It took me over a year to figure out it was noise introduced by voltage drop because of insufficient power distribution. Beware of this! and good luck!

BTW this was when I was very young and I had no scope, just a primative DMM.

My bit of advice if you want to skip over all my blah blah blah, is to pay attention to power distribution. Observe the voltages on every IC, even if your initial circuit works, and make notes.

Again, good luck!