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6502 PRIMER: Building your own 6502 computer


Basic Workbench Equipment

Obviously you will need a power supply to power your creation, probably 5V.  There are plenty of possibilities, ranging from batteries (not discussed here) to wall-warts (you probably use a small version of a wall-wart to charge your phone) to nice, adjustable workbench power supplies with voltage and current meters.  If you use a wall-wart, make sure it's regulated at 5V, or put a regulator on your computer board.  The LM7805 is a popular one that's simple to use, and tough.  Be sure to put .1µF capacitors at its input and output, close to the pins.  I use the Global Specialites 1310 which is a triple power supply (and is actually good for quite a bit more current on the two variable-voltage supplies that the specifications say) and looks like this:

Global 1310

The 1300 which you might find on eBay is the same thing from the 1980's but with an analog meter instead of digital.  These two have an outstanding reliability record.  They have three separate, isolated outputs:  a 5V one, and two that are labeled 1.3V-20V and 1/4 amp but are good for at least twice that much current and a little wider voltage range too.  These two are good for separate higher-voltage plus and minus slupplies for your projects, like you might need for op amps, the negative LCD backplane voltage needed by supertwist LCDs, analog switches, etc., and since they're there, you can run RS-232 line drivers like the MC145406 off of them instead of using something like the well known MAX232 which takes more space because of the external capacitors it requires and the extra pins to connect them.  Edit, Dec 2016: Apparently Global has discontinued the 1310.  There is however the 1301 with twice the current capacity:

Global 1301

Whatever power supply you use, make sure it does not overshoot the desired voltage for an instant when you turn it on, as that could damage the ICs in the computer you just made.  (I mention this because I've seen some integrated switching regulators that do overshoot upon turn-on.)  Also, if it is adjustable, make sure you verify the correct voltage before powering the computer up, unless the computer has its own 5V regulator.



You will also need a decent DMM (digital multimeter).  Actually, it doesn't particularly need to be digital, but most of them are today, and I've never seen an analog one with capacitance tester, frequency counter, transistor tester, diode test, or beep-on-continuity which come pretty standard on mid-range DMMs.  The analog ones generally are not as sensitive either.  You don't have to spend $100 let alone $400, but $25 probably is not enough.  There are plenty of good ones starting at $40-$60.  Go to Jameco's (or other distributor's) website and put "DMM" in the search bar.  I'm still using a Metex M-3650 I bought from Jameco in the 1980's, and operationally it seems to still be in brand-new condition.



An oscilloscope is not an absolute necessity, but it's awfully good to have.  If you can afford one, then it's a necessity!  :D  Basic new ones seem to start around $350.  It needs to be at least dual-trace, triggered, and 20MHz.  Basic stand-alone 'scopes now seem to meet all of those, in fact start at 40MHz or more which is good.  Pocket digital ones made for audio probably will not do you much good for your home-made-computer hobby.  One thing I will insist on is that you get a good pair of probes, and use them in the x10 switch position.  In the x10 position, the oscilloscope's .1V-per-division setting becomes 1V per division, and so on; but probes are never any good for the higher speeds in the x1 position!  If you buy a new 'scope, it will come with probes.  Take care of them, because they're not cheap to replace.  There's a lot more to good probes than meets the eye, and a decent pair for a low-end oscilloscope will cost you at least $40 or $50.  (They can be many times that price for the faster 'scopes!)  If you get a used 'scope, either be sure you get good probes with it, or budget some money to buy some.

Dave Jones has a rant about oscilloscopes on his EEVBlog #86, and frankly, he's right.  His basic message in this one is that cheap 'scopes like the DSO Nano are worthless; and after seeing his review of it, I totally agree!  His recommendation—actually his pleading, after all the times he's been asked about the cheapie 'scopes—is that if you're on a tight budget, then get yourself a used, basic 20MHz dual-trace triggered oscilloscope which you can sometimes even get for free these days.  I came across this video review of an oscilloscope attachment and ap for the iPad or iPhone on EEWeb, which I mention because like so many of these that seem to be a nice shortcut way to get something we used to have to pay a lot more for, they say it's very nice to use but its technical specifications are very poor, with only one analog channel, 5MHz bandwidth, 500mV/div with the probe on x10, and a 240-sample screen, which are not adequate for the work we're addressing in this 6502 primer.

A couple of good 6502.org forum topics on oscilloscopes are:
Cheap oscilloscope and other test equipment and
Recommended oscilloscope features?



A logic probe is cheap but not very often useful.  I've never had one, but it wouldn't hurt to get one if you want to, especially if you don't get an oscilloscope.



I have other pieces of equipment but not anything I would really say you need to get, at least to start.  Working for very small, low-budget companies for the last 30 years (which I enjoy), I have not had access to much expensive equipment, and being creative, I have been able to substitute for a lot of equipment using by home-made workbench computer and/or breadboards that didn't take long to make.  (My job is circuit design, mostly analog but a little digital, so I better be able to whip up that kind of stuff!)

There's a forum topic on low-budget equipment buying and making that especially deals with oscilloscopes here, and one that is all about oscilloscopes here (3 pages so far).  (These are the same ones linked above.)

Dave Jones has a video blog on setting up an electronics lab, at https://www.youtube.com/watch?v=R_PbjbRaO2E.  I posted about it on the sparkfun forum in response to someone's question, and the OP said he didn't think he would need 90% of that stuff.  But like Dave said near the end, a lot of that stuff gets accumulated slowly over the years.  He discusses the very basics at the beginning though, and I definitely agree with most of it.  I've seen here where beginners really cause themselves a lot of trouble and frustration by not getting for example a good DMM and power supply like Dave talks about, and a basic 20MHz dual-trace, triggered analog oscilloscope.  Without an oscilloscope, you're kind of working in the dark.  It's far more important than some of the things (like simulators) that beginners think they need.


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last updated Dec 21, 2016