Hi,

After a long time dedicated to my PDP-11 systems I plan to return to the 6502 world for some fun projects. And I'm planning to use again CPLDs for the Glue logic of course, it's just so easy. First I wanted to test some ideas on a breadboard. Up to now I was using a generic TQFP-44 to DIL adapter to bring the small ATF1504 CPLDs to the breadboard which always required to connect all power pins correctly and use a 10-Pin IDC adapter and wires for the JTAG to program the CPLD. Many times this was a source of error. Therefore I decided to come up with my own, ATF1504 specific, breadboard adapter



This adapter includes a wired JTAG interface and has the option to add some test pins for GND and VCC and there is also a place to put a power indicator LED to inform me when power is applied to the breadboard. At the bottom there are 4 decoupling capacitors to make the breadboard life easier. The adaptor has the size of a DIL-44 package. If interested I can provide Eagle and Gerber files.

P.S.: I'm planning to do the same for the AVR Atmega1284P with an ISP AVR interface and a crystal with load capacitors, as I will probably use this as the bootloader for the 6502 system.

I did this for my Ruby system, although I used the standard 40 pin DIL version of the 1284p and a can oscillator. https://projects.drogon.net/6502-ruby/ It's used for bootstrap, OS loading and filesystem interface as well as serial.

Cheers,

-Gordon

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

I see, you had the same issues, fast ROM is not available, and used the Atmega1284P to preload the RAM with a boot image. I solved it as well with the help of an Atmega in my ROMulus projects (not yet on my homepages https://www.5volts.ch/, but comming soon now). Some information you can find in this forum. The difference is, that I control RESET and PHI2 for the boot process and not BE and RDY as you do. And that's why I will have a Atmega1284P adapter to get ROMulus V3 on a breadboard.

An alternative to using a full microcontroller is to program a small cpld to copy the code from ROM to ram at startup. Easiest is to set it up to emulate a small rom with a copy routine.

Or even a GAL acting as a ROM - as was posted on the forum recently (can't find the link right now, sorry). I think they said it could hold about 49 bytes which might be just about enough for e.g. a serial bootloader.. It might be an interesting challenge..

Ah, here we are: viewtopic.php?p=71973#p71973

-Gordon

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

That board looks amazing! I would love the gerbers if they are available.

Also, are you using WinCUPL or something else to program that CPLD?

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Cat; the other white meat.

no idea if anyone asked for this, but i also made an adapter. mostly because i wanted to experiment with the ATF1504 before putting it into my SBC.

it doesn't have a key'd JTAG connector and obviously is a lot wider than cbscpe's design (which means you likely need 1 breadboard per side).
but therefore has the pin number written on it (and what it does, IO, GCLK, etc), uses the PLCC version of the chip, and combines all Vcc and GND lines together into one, to save wiring them on a breadboard.

i tested it myself and it works perfectly fine. (kinda hard to screw up a breakout board but i had to be sure)

in case anyone is interested here are the gerber files, you can just straight up upload this ZIP file to a PCB manufacturer, for example JLCPCB and it should work, since i did the exact same thing to get mine.
DROPBOX

I'm considering an ATF1504 for a future build, so that would be just the sort of thing I'm after for prototyping and experimentation. Thanks!

I finally found the time to update my webpage with the information about my own breadboard adapters. There you can also download the GERBER files

https://www.5volts.ch/posts/adapters/

Have fun

Peter