oops; I still almost made the same error; I should price/shop for for 74AC as well; and get pdfs and read them too!

I am reading all the old (last months) posts a second time; I am not known for shirking other people's good advice; at least without good reason; this stuff is complex, and I must let it "stew" and "percolate' in my brain.

A few of my posts indicate I will stress what is physically possibly, given the tools of the 6502 hobbyist. So, 74AC chips would be wise to have around. (I don't think my decoder circuit will have TTL logic 74xxs, so ACT or HCT should not be necessary?!).

One of my books has a 3 X 74318 and 1 X 74319 circuit wired as a 5 to 32 decoder. I don't think this is necessary, but maybe it is? The 64816 has a lot of address space????!! If I look for bigger )total Bytes) RAM chips, then I might need less decoding? I dunno? It's all new to me!

_________________
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?

Have spent the afternoon researching focal plane arrays (again). I have gotten out of the habit, but I should try to stay abreast of the subject.

I mention this, because my reply will undoubtedly focus, obsessively, on technologies I cannot possibly grasp adequately. I cling, in desperation, to your (collective/6502-group) hardware wisdom!

I guess I almost chuckle, when I think of using the 6502 to make something worthwhile. The CMOS sensors I purchased from Kodak (Kodak-ISS out of business; spun off, venture-vultured, then sold to ON semiconductor, who seems to have kept the CCD line and updated? and renamed? the CMOS line?), as dimly understood as the were by me, probably have equivalent processing power to the good ole 6502!

But I digress. I probably read half your primer, but my thoughts about it are still disorganized. I think address decoding and memory map are coming into focus. Had the old Wakerly "digital design" text out today, to refresh my memory (pun intended.... was studying DRAM and SRAM two nights ago) about propagation delay; 1 to 5 ns (I think?) per foot of PCB trace. Seems decent, given the prop. delays in chips, but I note that one must be cautious and read the pdfs carefully to understand "chip-delay" (several #'s are cited, depending upon the function of the chip, for the task at hand).

I think, if the decoding is not too complex, I will settle on 24KB RAM ($0000 - $5FFF) ; 16 KB I/O ($6000 - $9FFF); and 24 KB ROM ($A000 - $FFFF). This will follow the rules for IRQ/NMI and RESET stuff, and for stack in RAM and it is an approximately equal division, so that no aspect of computers function is too neglected.

So, I still want to design for immediate upgrade capability (i.e. to fully 65816 functionality), but was a bit stymied by the digikey offerings of DIP Asynchronyous Static RAM. 16MB addressable space, but the RAM chips (in DIP) are quite small?

Did I find a DRAM last night, of 512 KB? 32QTY of those would fill the space (or, 20QTY or so, leaving a little more for ROM or I/O)? Maybe I should see what Mouser offers?

I will keep wire wrap in mind. In fact, I might begin to "swear by it". I had difficulty when trying to design my focal plane array (5 or 6 or so years ago), as things were mighty crowded. At one point I decided to saw through the board and slide perpendicular boards into place. That was maybe a a mistake, though if I followed through I could have made it work (a couple of screws to physically fasten it in place, then solder the pad to the pads, or more liekly with a jumper wire between the two).

When I realized how ridiculous my sawing was, I purchased some molex (ribbon) connectors. And the project stopped there; life intruded, so i shelved it. Then Kodak/digikey stopped selling; I needed 9 CMOS sensors; I had 6 of the same kind and 3 or 4 more of different type.

I noted your advice against "running the bus out to the backplane", and then noted your exception to the rule. I will follow the thread/link--to the guy who did it properly--but haven't had a chance to, yet.

I might give my old "focal plane array" project a second try, since the CMOS sensors have come down in price (5$ per, in some instances). maybe something of the Kodak-sensor project can still be salvaged? I don't know.

I have some colloidal silver solution (or was it graphite?) for making plated through holes, but never got to that step last time. Also, if I remember right, there was alot of stuff about "deburring the holes" before electroless plating. I don't know. Maybe I was in over my head, for a hobbyist.

I have been searching through my materials, and I realized I have alot of materials and tools ready for the upcoming projects. I just need a little more organization, patience, and elbow grease.

Tell me (Garth or anybody else with an opinion) what you think of "molex-ing", i.e. tiny ribbon cables, the entirety of the CMOS image sensor (PLCC 48?-pin?) pinouts to a perpendicular board (literally "backplane" as the "frontplane" will need to be clear, so the lens can throw the image at the sensors)? How about connectors like a DIMM or SIMM has? You know, those heavy-duty, black-plastic connectors, made to handle those wide land-pads?

You're right Garth; Wire wrap is looking better all the time. Any drawbacks, in terms of AC operation? High frequency digital signals?

I wish I had the skills (and cash) to design using CCD; maybe even 3-CCD, trichroic prism assembly! Oh well; maybe next time.

Thanks for the info on the VIA; I am not a very "proprietary" guy; nor am I very "software".... YET!

Let us hope, someday, I can make a living as a scientist, and leave all this "$-talk" behind me! I very much want to push the ideas, instead of letting the $-ideas push me!

P.S. wire wrap needs me to buy posts and wire and different solder (I think?) and some connectors/sockets and such? Although, I did like how neat it looked, and I also liked those "stacked RAMs" you had. However, as previously mentioned, I might even have a problem making a doublesided board (unless I can drill holes, and run jumpers from a land on one side of the board, to a "land+trace" on the other side of the board? Can that be done? Or is that an "intermittent-electrical-problem" waiting to happen?).

Whooops; idiotic "wire wrap = no solder" . My bad! Spoke/wrote too fast!

Ever hear of "tyranny of wires" .... I think it is a known phrase. I am sure it has "made the rounds" among "computer circles". (Come to think of it, I think my father's first job, as a teen back in the early 60s, was to take the piecework off the end of the bench on production line; I think it was mostly women in the factory, wiring up the backs of RCA TV sets? funny story!)

OK, last night I was looking at some SRAM: Alliance memory Inc. ;

"The AS6C4008 is a 4,194,304-bit low power CMOS static random access memory organized as 524,288 words by 8 bits. It is fabricated using very high performance, high reliability CMOS technology. Its standby current is stable within the range of operating temperature.
The AS6C4008 is well designed for very low power system applications, and particularly well suited for battery back-up non-volatile memory application.
The AS6C4008 operates from a single power supply of 2.7V~ 5.5Vand all inputs and outputs are fully TTL compatible"

Does this seem suitable? I note the 55 ns propagation delay, and I noticed one of your posts says that is not good enough (perhaps if I run the clock at 1 MHz?)? ( viewtopic.php?f=4&t=573&p=32004#p32004 )

_________________
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?

Thanks a zillion (your site is neat! But I over-use it. More wires, less talk/type! I was looking at the user list, and noted that one could search by # of posts. I think I was 107th, with 38 posts! Far too much for guy who never ran a processor! Also, I will limit my discussion of image sensors, as that is off topic--that is, until I get my focal plane array up and running! Then, when I run into I2C problems, I will seek knowledgeable people!). I have TONS of work to do (preparation, workbench, purchase tools), before I can start working on the really interesting digital projects (I don't mean to "diss" the 6502, but I just clearly have a different purpose; vision science). Thanks a zillion.