randallmeyer2000 wrote:
I still need (1) an oscillator can (2) a reset button (though, my local radio shack will have one)
Radio Shack will have a few things when you need it right now and can't wait for an order to come; but generally you'll pay way too much there, if they have the part at all. If you can wait long enough to receive an order and can buy enough parts to make the few dollars of shipping worth it, I would suggest getting familiar with
Jameco,
Mouser, and
Digi-Key. You can do online-only if you like, but they do all have paper catalogs, unlike many industrial distributors. Jameco's catalog is the most oriented toward hobbyists and is only about 170 pages, with lots of color pictures. The other two have paper catalogs of about
2500 pages, with much smaller printing, and nearly everything is in stock, and in fact they stock a lot of things that aren't in the paper catalogs! We (the company I work at) use Mouser and Digi-Key a lot for production parts. For prototyping and hobby parts I sometimes use Jameco as well. I suppose that after I form parts lists, the company buyer probably collates them and sends a spreadsheet to the distributor, but I like to call them up with credit card in hand and list with exact stock numbers and quantities and prices in front of me. The process is very quick, especially after they have my address and other info on file. (Having the price there in front of me serves as a cross-check to make sure I got the right stock number. If the price they tell me doesn't match, I can see where the error is.)
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(3) a 3-input And gate, (4) a pin/holder-thingy for your expansion board and (5) your expansion/memory board
If you mean the memory board, I can supply the sockets as well when you order. I have both soldertail and wire-wrap. I just pass them on for my cost (which will probably be less than your cost since I buy in larger quantities).
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And power supply (which I haven't thought much about! I don't suppose a 6 VDC, wall-wart and 7805 with a few electrolytic capcitors would work fine, would it?)
The 7805 requires a little more voltage to be able to regulate. You shouldn't let the input drop below about 7V. Put monolithic ceramic capacitors at the input and output too, super close to the 7805.
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So, a few small question; buses, both address and data, generally "fan-out", right? I mean, the whole bus trace is "driven" but because of the chip select, only one chip is "listening" at any one moment? So, my PCB traces for each address pin, or data pin, will generally branch into 3 or 4 or 5 different locations, right?
Yes. "Fanout" generally refers to DC loads though, and CMOS presents essentially
no DC load, only a little input capacitance (a few pF). If you had a huge number of these loads, it can slow things down a bit, but in your case it probably won't affect your design significantly.
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Regarding clock, your primer didn't seem to comment much on the '816. I will read it over again, but from the '816 schematic it seems there is only one clock pin, and it is an input (called Phi-2, I think?).
The 6502 primer is just that, a primer, so it's pretty basic. Most people going on to the '816 have already gotten their feet wet on the 6502. I also don't have much experience on the '816 as far as hardware goes. I have the 65
802 in my workbench computer which is an '816 made to drop into an 6502 socket; so although it still offers tons of benefits, it is confined to the 64KB address space of the '02. I wrote a rather full-featured Forth kernel for the '802, and found it to be actually
easier to program than the 6502 when constantly dealing with 16-bit values.
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My question about 2n2907 was for a slightly different project; a fiber optic, TTL signal, LED driver. I bought a discrete one at radio shack on Monday; for 1$ I couldn't say no.
If you're there and see it and you need it now, perfect. Get it. But again, realize that RS charges way too much otherwise. The PN2907 is basically the same thing in the cheaper molded plastic case instead of the can, and we buy the PN2907A, 2N3906, 2N4401, MMBT3906, MMBT4401, etc. for anywhere from one and a half to four cents each in quantity. Even in singles, you'll pay about one-fifth of the RS prices if you buy from a place like Mouser.
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I think my decoder circuitry will require a 74138 (ordered and paid for, in the mail) and a 3-input And gate. Texas instruments offers $0.50 or so chips, with something like 8 to 10 ns propagation delay, so I'll probably order that soon.
If there aren't any letters after the "74," it will be the old-fashioned TTL which, worst of all, presents an extremely heavy load at its inputs. Use CMOS, like 74HC, 74HCT, 74AC, 74ACT, etc.. If you need it right now and RS has it but not in CMOS, at least get 74LS, not just 74. I'd still advise going with CMOS as much as possible though.
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for I/O a 2-input-AND can chip enable (but does 6522 work like that? is there a CE pin
The '22 has two CE inputs, one being positive logic and one being negative. Use that to your advantage. It simplifies the glue logic.
About the clock line in your last post: Don't worry about running it close to other stuff. When it matters most, you'll use a ground plane anyway, and also observe the other things written there about groundbounce and things that are at least as much if not more of a concern.