I'm considering using some custom logic for the 6502/65816 builds I'm working on. And while I've found some information from searching the internet, seems like information on these devices is a bit of hit or miss; and I feel I'm still just about puzzled by what's out there when I first began my searching.

I did manage to pick up some ATF16V8 PLDs, and figured out how to program those and get them working; but I've quickly run into limits with what those can do, and I think in order to do some of the more complex things I'd like to do, I will need to move on to some CPLDs and/or FPGAs. As such I have some questions surrounding these things that I'm having trouble figuring out from internet searches.

FPGAs:
I did pick up a development board with an FPGA, and have tinkered with it a bit, but I'm not yet clear how I'd go about integrating it with my projects.

It looks like a good chunk of these are using 3.3V logic which would require some logic level shifting which I'd like to avoid if for no other reason then it's just adding more chips to the mix that add delays, and soldering work (they have a lot of pins!) and what not? (Maybe I'm over thinking it?) Are there any 5V CMOS options out there?

I've also noticed that, the board I have has a lot of support chips around the FPGA itself. I'm presuming some of these are just fancy things showing off what you can do with the FPGA, but I was wondering about how you go about programming just the raw FPGA itself. From my searching I want to say that seems what this JTAG thing is for, but all the information I can find is pretty sparse on details. With the PLD I have I can just drop them in my EEPROM programmer and call it done, but I don't think I'm going to find such a device that fits most of the surface mount packages I'm seeing the FPGAs in.

Finally, I'm a bit on the fence about these as they seem really powerful, esp. compared to the 65xxx chips, which begs the question of why would I not just use them to just include the CPU in them to begin with? (Just seems weird to slave the more powerful device off of the less capable chip like that, just curious what people think about this.)

CPLDs:
The CPLDs seemed interesting because it seems like they wouldn't just immediately overshadow the 65xxx processors, and are limited to more discrete logic operations. It also appears that there are some more 5V options.

However, they have the some of the same programming questions as the FPGA. Most appear to be PLCC or surface mount; what do you guys use to program these things?

The idea of having logic implemented in a re-programmable hardware language seems really appealing to me so I'd really like to learn more about these guys.

I think the programmable logic route can be a very fine adventure!

You're right, the relative lack of 5V parts, or even 3V parts with 5 tolerance, is a bit of an obstacle, but it's not a barrier. It's fairly likely you'll need level shifters, either in your own design or built into a submodule that you make use of. These days a PCB house will often have an affordable option to include components, so if you pick parts from their list they will do some of the assembly for you. Another option is to use a dev board which already has what you want. (If it happens to have more, that's no problem.)

And yes, if you pick a capacious FPGA, it might well be large enough to contain a CPU, and that can be an interesting option. But you don't have to do it if you don't want to. One attraction of 8 bit computing is to have access to the address and data busses, and one attraction is to have a 40 pin DIP that you can point at as the CPU. Tastes vary, and there are many ways forward.

Both CPLDs and FPGAs will most probably be programmed over JTAG, which means there'll be a header, maybe 6 pins or 10 pins, maybe with a standard pinout, and you'll need something to program the device. That something could be a proprietary dongle, or it could be a Raspberry Pi (or Pico) or it could be something in between.

Have a good adventure, and keep in touch. Do some reading, ask some questions, do some experiments.

There are many previous posts and threads too, so have a look around.

I've used some GALs (22v10s) in my 6502/816 boards. Plenty old Lattice ones on ebay and compatible ATF ones (that need a different programmer) still in production.

For designing the logic I used GALASM which runs under Linux for me.

-Gordon

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--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

That's good to know, I might have them handle the surface mount stuff which I'm just clumsy with.



Not going to lie, there is something very satisfying about snapping an IC into a bread board or socket, almost like building a Lego set.



Okay, I was thinking at least for the PLCC chips I could probably get a socket and make a small board with whatever I need to do it. Are the pins in usually suspect locations like VCC and Ground often are for 74 chips?



Yep, I've been poking around I has the brain juices flowing.

A couple more outputs than the 16V8s, but I need at least 11 lines for my address decoding I'm doing. >_<
Which is the first thing I was planning to try and use them for, I currently have 3~4 ICs handling that logic and I'd like to reduce that down to one IC and get the propagation delay down so I can look at boosting the clock speed on my 6502.

I've been eyeballing these ATF1502AS-7JX44 jobs, which seems like they'd have more than enough to do what I'd like initially. Seems like I could get my address decoding in there, plus (I hope) something to shadow the ROM into a faster RAM chip and then have it switch the clock on boot.



I'll check that out WinCupl is clearly a bit dated and has some.... ah.... "personality" let's say.

Oh, you'd normally program with JTAG in-circuit, no need to socket your chips, unless you expect to be swapping them for other reasons.

hmmm, i would personally always put PLCC and DIP chips in sockets, regardless of if you actually plan on taking them out again or not.
simply having the option to take them out without doing any desoldering is always nice to have.

but as Ed said, JTAG is designed for in-system programming, so you program the CPLD/FPGA while it's in your system using an onboard JTAG header.
said header has a standardized pinout, for the AT150x series of CPLDs it's this:

also make sure to never use the JATG Pins for your logic, as that will disable JTAG. which casues some headaches!

also in regards to the voltage, 5V FPGAs pretty much don't exist (technically they do, but are too expensive to be worth it). but if you really want to use an FPGA, then you could design your whole system to run on 3.3V instead.
it shouldn't be that difficult, unless you plan on using some part that requires 5V signals, but even then you could connect that one using level shifters and have everything else still run at 3.3V.
though of course this is only really an option if you're planning a new system, and not when you already have one where you want to replace the existing logic with an FPGA.


hm, if you're using a 65c02 have you thought about making a simple RDY circuit to slow the CPU down when accessing the ROM?
obviously you lose some performance, but it seems much easier to implement. plus later on you can then go back and redo that logic to allow the CPU to disable the ROM (which then also disabled the RDY circuit).


i found that using the commandline CUPL program directly works better.
alternatively you can use Verilog/VHDL with Quartus II web edition v13.0.
make your project around the MAX7000 series:
MAX7032 = ATF1502
MAX7064 = ATF1504
MAX7128 = ATF1508
then after synthesizing, use POF2JED to... well convert the .pof file from Quartus to a .jed file to program into the CPLD

it's a bit of a process, but i've been using it for years now and it works well enough.
but this sadly won't be an option if you're on Linux.

Programmer for ATF150x is pretty expensive, over $60 last time I checked. EPM7xxx is equivalent to ATF150x but EPM7xxx programmer is cheap, under $10, shipping included. Designing EPM7xxx can be done with free-download Quartus tool, version 13 or earlier. The tool chain is straightforward. The big IF is where to find reliable EPM7xxx? You can try eBay only because of its excellent return policy because you'll like return many of them. If you do find a reliable source, buy bunch of them. You'll like CPLD so much, you'll regret only have purchased 10-20 of them from known good source.

You can pack lots of functions into even a 64-macrocell CPLD (ATF1504 or EPM7064S) such as a 64-byte boot ROM, serial port, I2C, compact flash interface, and address decode.
Bill

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

Cool, thanks for the feedback guys.

It looks like the ATF chips are easy enough to get from someplace like Mouser/DigiKey. Looks like I can get them setup with JTAG, so I'll clearly need to learn more about how that works.

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

I'll keep that in mind, I haven't had a chance to really sink my teeth into the 65C816 I got, but I am really interested in trying it out. (I wanted to get my feet wet with the 65C02 first)



I have one of those programmers, I was trying to use it with some PIC chips, but the software seemed to loose all notion that the device was there after one program. I'd have to restart their IDE if I wanted to reprogram it.

I'm a bit leery of it as I ended up frying the first programmer and my PS/2 keyboard trying to get a PIC chip to act as a keyboard controller; I'll have to try again some day. (To be honest I'm considering using one of those USB host controller chips that has an SPI interface for things like keyboards, mice, and game controllers)



Good to know. Most of my work space is pretty cramped right now anyhow. The workspace I have sits about 3' from the front panel USB ports on my main computer. (I need to get another table in here for the electronics stuff I've started working on. XD )

Ooooff..... Been struggling with this for a couple of hours now just today.
WinCupl crashes on my design file (though I do get a JED out of the deal)
Trying to run the cupl command prompt doesn't seem to generate a JED file. (It doesn't error either)

Thought I might try and get Quartus to do it (I want to get better with Verilog anyhow), but I can't seem to get the MAX7000 series installed as a supported device for a new project. Quartus does work with the Cyclone V development board I have though. Also have it compiling to an Lattice ICE board I got from nandland.com so I know Quartus itself "works" (at least for those two devices)

Here's the output and my command I'm issuing to cupl for reference.


I also attached the PLD file on the off chance that's relevant.


As for Quartus I managed to track down the MAX device file qdz, but the installer refused to recognize it. I tried hacking the name, which got it to recognize the file, but it claims it's already installed, but MAX7000 isn't an option when I create a new project.

Any thoughts?

Nevermind the upload didn't like that. Here's the raw dump:

the ATF15xx series require more than 1 command to work.
i made myself a little batch file that would ask for what ATF15xx chip i'm synthesising for, and then does the correct command.

(%inputN% is the name of the input file without extension)

it works for me, and even generates a .fit file, which is always useful to have as it shows the exact pin placements (in case you didn't assign pins manually) and also tells you how "full" the chip is.

for the GAL22Vxx, you only need the first command.
also make sure %PATH% contains the path to both CUPL, and the FIT15xx executables. and you also need an envrioment variable called LIBCUPL that points to \Shared\cupl.dl, wherever that might be on your system.

EDIT: the -dev option for the FIT15xx executables is not needed, as the PLD file already specifies the exact chip/package.