74HCT6526 SBC TestBed

[daniMolina]

All my repositories are now public.

GitHub repos:
SBC6526 https://github.com/dmolinagarcia/SBC6526
LOGISIM6526 https://github.com/dmolinagarcia/LOGISIM6526
74HCT6526 https://github.com/dmolinagarcia/74HCT6526

Of course... everything is untested, experimental, and may catch fire if anyone tries to build their own.

[daniMolina]

SBC6526 v2.0 has been commited into the repository, and it's now production ready. As soon as a second PCB I need is ready too, I'll be sending it to the fab

You can find the full schematic attached in this post.

Cheers!

[daniMolina]

Hi all.

New year, new goals, new(-ish) builds!

After procastinating for a while... I've finally come around building SBC6526v2. And, apart from a blown up LCD screen... which I've been unable to explain, everything worked like a charm.

Main improvements from v1 are as follows:

• Much better layout, fixing some issues found on v1.
• Mounting holes match those on 74HCT6526. Also a 40 pin port is on the bottom layer of the PCB, so the 74HC6526 can stack directly below SBC6526. Bye Bye ugly looking ribbon cable! Also, mounting holes act as GND and VCC rails, hopefully improving 74HCT6526 stability.
• 6522 now controls the LCD. In V1 this was done with 6526 so, everytime I reset the 6526 (It could be reset independently) the LCD crashed and many times, it didn't recover. Now LCD works all the time, no issues
• Space for two 6526. First one directly on board (left-most IC in picture below). Second one connected to the bottom port. (See last picture)
• Migrated to 4 layer layout. Even though v1 reached 16MHZ with no issues, I'm moving all my designs to 4layers.

Having two 6526s on board (Both of then can be original NMOS ICs, or any modern replacement), and not having them performing any function for the SBC, I can run tests on them, comparing behaviours between them, and hopefully, give a very much needed push to my other project.

As usual, everything is published in https://github.com/dmolinagarcia/SBC6526

Feel free to use, explore, and criticize if needed. Everything will be welcomed.

Cheers!