Super Breakout (MK 28000?) to 2716 adapter

klke

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I have a Super Breakout rev-03 non working PCB that I would like to start troubleshooting, for that I would like to convert to rev-04 that has just 3 proms and strap 2716.
Digging on the forum I found a thread about that were HudsonArcade posted valuable information:

C1, D1, E1 are the 8-bit proms, but it can be populated with 4 bit proms instead (4x 4-bit PROMs per 8-bit PROM)

C1 = ROM2 = /PROM3 + /PROM4 = J0 + J1 + L0 + L1
D1 = ROM3 = /PROM5 + /PROM6 = L0 + L1 + M0 + M1
D2 = ROM4 = /PROM7 + /PROM8 = N0 + N1 + P0 + P1

Unfortunately the M28000 to 2716 adapters I posted for free on OSHPARK need to have the /OEs inverted to be used on super breakout, so those won't work for you.

I did a high score save kit that replaces the PROMs with a CPU plugin, but I never got around to testing on real hardware.

I found his MK28000 to 2716 adapter pcb design on Oshpark and was trying to find the way to adapt so Super Breakout, this is the rev-04 rom addressing schema that I found on the Atari Superbreakout Cabinet manual:

image.jpg

When I read HudsonArcade answer I was thinking that maybe I would modify his original adapter to add a IC 7404 to invert OE signals and make it work. I started to enumerate pins of his adapter and validate it with mk28000 and 2716 schemas:

MK28000-TO-2716).jpg
And I made a comparison table on excel:
image (1).jpg

But I saw that OE signal pins of MK28000 are not pointing to any pin.
At this point, due to my complete ignorance of circuits I am absolutely lost maybe someone can help me.
Seems there are not many info about this board and how to strap other eproms besides the famous Grant Searle 2008 restoration thread.

Edit: Just wanted to document a bit Grant Searle adapter
ProgramRomBottom.jpg
 
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That board was made for Tank where the outputs are always enabled, so ~CE and ~OE are grounded.

For this application, you'd need to cut the trace that grounds ~CE and ~OE and tie that to (generated) ~ROM2/3/4 signals.

It doesn't look like the first gate of D0 used, so you should be able to pull the 7400 and replace it with a 7408 to invert ROM2/3/4, then wire the floating via to pin 14 (or 24) on the mk28000 side.


1724162286691.png
 
That board was made for Tank where the outputs are always enabled, so ~CE and ~OE are grounded.

For this application, you'd need to cut the trace that grounds ~CE and ~OE and tie that to (generated) ~ROM2/3/4 signals.

It doesn't look like the first gate of D0 used, so you should be able to pull the 7400 and replace it with a 7408 to invert ROM2/3/4, then wire the floating via to pin 14 (or 24) on the mk28000 side.


View attachment 763250
Wow this is a very simple aproach, like that I even don't need to make another pcb, I will print yours and cut/jump traces :love:
I am gonna try and I will leave feedback, many thanks
 
If you're going to bother to get board made, do this instead:

Plugs into the CPU socket, and uses a 2764, so you'll only need 1 ROM and 1 board.

(You'll still need to remove any program ROMs/PROMs since doing the decode with 1 chip didn't leave space for a buffer to disable any chips on the board during a ROM access.

1724249753078.png
 
For documentation, here's what Grant did:
1724253014996.png

~ROM is just the NOR3 of ROM2/3/4

A11 is ~ROM3 (implemented with a NOR3)
A12 is ~ROM2 (implemented with a NOR3)
 
If you're going to bother to get board made, do this instead:

Plugs into the CPU socket, and uses a 2764, so you'll only need 1 ROM and 1 board.

(You'll still need to remove any program ROMs/PROMs since doing the decode with 1 chip didn't leave space for a buffer to disable any chips on the board during a ROM access.

View attachment 763409
Wow amazing thanks a lot, this is an awesome solution.
I am analysing it and I am gonna try to design it on kicad (or maybe I will try to fill out tracks and holes and use something like this tool Image2pcb as a complete noob on this field)
I have a question, are OE 22 and CE 20 from 2764 tied together and going to SN74LS00 pin 8? So if A11 and A12 are true will send false to output enable, is it right?

1724249753078 (2).png

Many thanks again for your patience 😅
 
It's doing this -- makes more sense it you demorgan U3:B and pop the bubbles.

I can just send over gerbers if you don't want to redraw in KiCAD.

View attachment 763511
I guest I got it:
Imagen pegada.png
Even if I am trying to redraw it KiCAD I would really appreciate if you send me your gerber files, I am afraid that probably I will do some step wrong and don't wanna have to reprint the pcb 🙏
 
Here's gerbers of the version with the buffer added so you don't need to remove ROMs/PROMs from the board.
~ROM enables the on-board eprom, so it's inversion enables the '245 to communicate with the rest of the board.

You can download Viewmate from pentalogix to view them.
 

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  • SBREAK_ROM_BUFF.zip
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Awesome work, this is a must have it for any Atari Super Breakout owner and for sure will help many people and prevent many cabinets to finish on the recycling center or converted to mame 😅 . Big thanks for your time and your effort.
I was checking it in jlcpcb and looks amazing, gonna print it right now and to buy the '245. I will leave feedback as soon as I get it.
 
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