1200XL Extender Card w/OS and BASIC

reifsnyderb · September 8

Since I was able to get OS 6.3 running in RAM, I figured it would be a good time to finish up a 1200XL Extender Card I had made.

Something I noticed about other 1200XL cartridge extender cards was that they had a lot of space and no ROM. So, I figured I'd put a ROM on it along with some other logic so as to upgrade the OS and have BASIC handy. This card has OS 6.3 installed so that it's now easy to run a newer OS without doing surgery on the computer. I also decided to install Altirra BASIC on it as well. There are two switches on the left. The front switch turns the card on and off. The back switch turns BASIC on and off. There is also logic, on the card, that detects if a cartridge is installed and automatically allows the card to act as a pass through.

This was also a nice test of the next OS version I am working on as it will change the LEDs on a 1200XL. Right now, L2 lights up during SIO access. 🙂

Back side shows how I had to modify the board as I figured things out.

Edited September 8 by reifsnyderb

reifsnyderb · September 9

I applied fixes and modifications to the design and have the next card design about ready. Since I needed 2 more 4.7k ohm resistors, I added them. Also, I wasn't happy with the location of 2 other 4.7k ohm resistors and moved them so there are 4 4.7k ohm resistors all lined up. The other trace changes have been made as well. I also added a dedicated bypass capacitor for the cartridge slot. It's probably not really needed....but it won't hurt to have it anyhow. I may do a couple more, minor, silk screen changes prior to ordering fixed cards. 🙂

Testing of the cartridge connector is successful. Unsurprisingly, the Side3 cartridge has to have the card turned off, but the pass-through still works. So this 1200XL Extender card doesn't have to be removed.