Does your system now work, Terrance?

Yes. Thanks.

And it worked from the start with the second set of code from my original post. This post wasn't about trying to get my hardware to work, I'd already managed that. I was trying to understand if the logic I used was doing what I thought it was.

Adrien showed in the first reply that it wasn't the same and that RAM_CS was active when writing to ROM. That's good to know, but not an issue in my system. I was happy to leave it there, but luckily others continued to comment. I've learned a lot more in the process. Everyone has helped expand my knowledge.

Good to know.


Yes, but if they are there for the taking, why not use them?


Yeah, I had noticed the PLD was only outputting 4V high. I'm not super happy about it. I'll keep an eye on it, but at this point I'm liking the flexibility I gained quite a bit.


Yes, I got some flip/flops to test this idea. Haven't got to it yet though. But using it will likely impact the features I can include in my design. Originally, I was using a 65C02 with a single chip address decoder and two VIAs, two ACIAs, a 3-input AND for the IRQs, and two other chips for USB serial and keyboard interface. This fit nicely on a 100x100 mm PCB. Moving to the 65816, I add at least two chips for the bank address latch and data bus buffer, and likely a larger SRAM. But I had no space on the PCB, see attached image. Something has to give. Right now I don't know what it will be.


I wouldn't say I'm stubbornly insisting on using negative logic, but I do admit struggling with the alternative. But I'm always up for a challenge. I compiled a positive logic version of my code and according to the WINCUPL DOC file it uses the exact same number of product term as the negative logic. I suppose there is more to it than that. If not then perhaps WINCUPL has been able to optimize my code in some way. I've attached the PLD (as txt files) and DOC files for anyone that's interested.

As for the use of minimization, does its use result in some inferior result? If not, I'm back where I was, why not use what's available, realizing of course, as you point out, that I'm on the ragged edge.

I’m late to the discussion. I’ll pleased to hear that GAL can drive output to 4V, that’s definitely CMOS level.

CPLD can certainly reduce your board size to 100mmX100mm, so can PLCC packages for 65816, 6551, and 6522.
Bill

A good idea that I've eyed before but since I'm already a poster child for BigEd's So many ways for projects to go wrong post, I think I might save this one for another build.

_________________
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!

Ok, maybe I'll bite. BigEd can print up a "Failure to Proceed" poster with my picture on it.

I'll have some research to do though. I bought a PLCC socket sometime ago just for the fun of it, but I don't see how I could possibly solder it to a PCB.

Hee hee. It would be a less wonderful world, I think, if there were only one acceptable design. So I advise considering carefully what the tradeoffs are, and what your own priorities are.

It can be particularly difficult to navigate exactly what datasheets say, and what they don't say, and to figure out how strictly to take them: knowing, as we do, that we're probably not operating with worst-case parts in worst-case conditions with high stakes. As BDD notes, our employment, or people's lives, generally do not depend on our hobby constructions. The tradeoffs are mainly about the risk of difficult debugging or unreliable operation. (If unreliable means it crashes within seconds, that's probably a problem. But if it crashes every few weeks of runtime, well, in many cases we might never notice.)

Yeah, I guess you can say I'm building to typical vs minimums. I've been blasted by some elsewhere for a design that's not technically to spec, but I'm not doing product design here or creating how-to videos. This is more about the journey for me. I want to know the technical considerations, but I'm ok with typical or actual specs, if the chips work for what I'm doing.

I know a lot of folks here are doing serious development, but for me, when (if ever) I'm done I'll likely move on to something entirely different and never pick the thing up again. After all, the smart display and PS/2 controller I'm using are in many ways significantly more powerful than either the 65C02 or 65C816. And there are much better hobby alternatives if all I cared about was processing power or getting things done.

One thing about going to PLCCs is that my build edges even closer to being a W65C816SXB development board clone, which is kind of in the opposite direction of your comment. But such a shift does open the door to, why not surface mount everything else on the board and then, why not have the PCB fabricator populate everything as well. Maybe not a bad idea. I've done plenty of soldering in my life and don't really need to focus on that part of the experience.


While frustrating, I probably get the most enjoyment from tracking down such bugs. And while I'm pleased when things work on the first try, I kind of miss that I didn't have an opportunity to troubleshoot something.

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

My original goal was to build something similar to the attached image. Things morphed after I discovered that the keypad was too limiting. But I've always kept to a handheld design and thus small PCB.


Ok, just googled, I suppose you're referring to a through hole socket. I didn't see those before. I bought a surface mount socket. Or are you saying that you solder those? If so, more power to you. I couldn't do it without melting the socket.

_________________
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?

For my build, the segmented display went out with the keypad. After trying out several different character displays, I decided I wanted something much more capable. I went with a 4D Systems smart display (I attached an image with it towards the bottom of page 1). It's pricey and actually in many ways much more capable than the system I'm building. But the 65xx processors can spit out data faster than the display can process, so that's something.