I use a GAL to reduce part count in this design. I’ve had a terrible time programming the GAL with a vintage Data I/O 29B and finally gave up and bought a cheap chinese programmer that seems to work better.

Prototype Prototype with LED on

After a few tweaks, especially surrounding the difficult timing on the 6522 VIA, I have the prototype up and running and even blinking a LED. I found an Apple tech note about interfacing to the 6522 that I decided to follow exactly. I had one other issue with handling the release of the selection of the C800-CFFF ram space. Some of the schematics I found online, use some inverters and a cap to slow down response to releasing the selection, presumably to ignore glitches. I found that using the same delayed clock to condition this signal as is used by the 6522 interface, seems to work as well.

I implemented the PROM on this device with an EEPROM and I have been able to write some small test programs and save them in EEPROM without any need for a prom programmer. I think experimenters are going to love this feature. I wish I had done this on the Brain Board, but I didn’t think of it at the time.

For Apple 1 lovers, note that I did a quick checkout in a Brain Board/Wozanium environment this morning and had no issues.

I have lots of ideas for projects and it will be easy to connect it to a solderless breadboard for quck and easy prototyping. Besides use for experienced hackers, I want to make this a tool for people who want to learn fundamentals of computer interfacing and hope I can find time to do a series of introductory projects. What it ends up doing, besides blinking a LED, and the projects I come up with, is up to the creative people in the Apple II community.

I’ll definitely bring the prototype to TCF east next month. I’ll have to figure out how much more testing is required before ordering a batch of boards. I’ll definitely try it in my IIe, but what else I run it in remains to be seen. The PCB layout has been tracking changes made in the prototype, so once I decide I have a good final design, it will not take long to get the boards made.